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IL Ranker Series Biology for NEET Grade 12 Module 1
ISBN 978-81-985044-5-6 [SECOND
EDITION]
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Dr. B. S. Rao, the visionary behind Sri Chaitanya Educational Institutions, is widely recognised for his significant contributions to education. His focus on providing high-quality education, especially in preparing students for JEE and NEET entrance exams, has positively impacted numerous lives. The creation of the IL Ranker Series is inspired by Dr. Rao’s vision. It aims to assist aspirants in realising their ambitions.
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As we pay homage to Dr. B. S. Rao’s enduring legacy, we acknowledge the privilege of contributing to the continuation of his vision. His remarkable journey serves as a poignant reminder of the profound impact education can have on individuals and societies.
With gratitude and inspiration
Team Infinity Learn by Sri Chaitanya
Preface
The IL Ranker Series for NEET is a comprehensive series of books designed to help students prepare for one of the most important exams on their path to becoming doctors or medical professionals. The National Eligibility cum Entrance Test (NEET) is a critical step for students aiming to enter the medical field, testing not only knowledge but also their ability to think and understand the application of the concepts. Recognising the skills needed to crack the NEET and the challenges the students face, this series has been crafted to serve as a guide, mentor, and companion on their path to achieving their dream rank in NEET.
The IL Ranker Series stands out because it's built keeping NEET aspirants in mind. We've included a variety of features to cater to their learning needs and to prepare them thoroughly for the exam.
This meticulously designed book series offers a comprehensive exploration of key concepts. Organised into clear topics and subtopics, it facilitates efficient learning. Practice questions and checkpoints solidify understanding, while illustrations and tables enhance visualisation and comprehension. Chapter reviews provide a quick revision tool, ensuring knowledge retention.
The comprehensive coverage of the NCERT syllabus is supplemented by advanced questions, providing holistic preparation for the NEET exam. It incorporates diverse question types, including matching, statement, assertion & reason, and brain teasers to enhance critical thinking and application skills. The resource includes expert tips, theory-based questions, and a mix of difficulty levels, aiming to improve conceptual understanding, cross-topic synthesis, and retention of key concepts.
This second edition of the IL Ranker Series for NEET is more than just a set of books. It's a commitment to help you learn, grow, and succeed. We've designed it to ignite your passion for the medical profession and to foster a lifelong love of learning. With every page you turn, you're moving one step closer to your dream of cracking NEET with a good rank.
Key Features of the Book
Chapter Outline
1.1 Flower – A Fascinating Organ of Angiosperms
1.2 Pre-fertilisation: Structures and Events
This outlines topics or learning outcomes students can gain from studying the chapter. It sets a framework for study and a roadmap for learning.
Boxed Text
This section includes supplementary information beyond the NCERT textbook to enhance understanding and expand knowledge.
Oestrogen is responsible for the initial growth and thickening of the endometrium during the proliferative phase, while progesterone helps maintain the endometrium and prepares it for potential pregnancy during the luteal phase.
The safe period refers to the phase when a woman is least likely to conceive. In a typical 28-day menstrual cycle, it extends from day 18 of a cyle to day 9 of the next cycle.
These include mnemonics for effortless memorisation, real-life examples, and more to enhance learning. Tips and Tricks
These questions gauge students’ understanding of the topic. Correct answers build confidence for moving to the next topic.
CHAPTER REVIEW
Reproductive Health - Problems and Strategies
■ According to the World Health Organisation (WHO), reproductive health means total wellbeing in all aspects of reproduction, i.e., physical, emotional, behavioural and social.
Checkpoint
Q. How can suckling by the first-born twin indirectly contribute to faster delivery of the second child?
Answer: Suckling stimulates the release of oxytocin.
It offers a concise overview of the chapter’s key points, acting as a quick revision tool before tests.
This is a focused practice with topic-wise questions based on NCERT textbook content. It is designed to enhance students’ success in NEET by aligning with recent exam trends.
Exercises
NEET DRILL FURTHER EXPLORATION
Holding substantial weightage in the NEET Biology paper, these questions improve analytical judgement of statements.
Known for their low scoring rate and high weightage in recent NEET exams, these questions play a crucial role in improving students’ critical thinking skills to assess the logical relationship between the assertion and the reason.
MATCHING TYPE QUESTIONS
STATEMENT TYPE QUESTIONS
ASSERTION AND REASON TYPE QUESTIONS
BRAIN TEASERS
FLASHBACK
CHAPTER TEST
Modelled after the NEET exam format, this test is based on a specific chapter. It serves as a tool for students to evaluate their time management skills and gauge their mastery level in a particular chapter.
This section comprises questions that extend beyond the NCERT content yet remain relevant to NEET, preparing students for additional and pertinent challenges beyond the textbook.
These include questions for practising the correlation of information across different topics. A significant number of matching questions appear in the NEET Biology paper and are easy to score.
These complex questions that combine fun and critical thinking are aimed at fostering higher order thinking skills and encourage analytical reasoning.
Hand-picked questions from previous years NEET offer an insight into the types of questions and the important topics that are probable to appear in NEET.
CHAPTER 1
SEXUAL REPRODUCTION IN FLOWERING PLANTS
Chapter Outline
1.1 Flower – A Fascinating Organ of Angiosperms
1.2 Pre-fertilisation: Structures and Events
1.3 Double Fertilisation
1.4 Post-fertilisation: Structures and Events
1.5 Apomixis and Polyembryony
The myriad of flowers we enjoy gazing at, the scents and perfumes we swoon over, and the rich colours that attract us are all there to aid
sexual reproduction. All flowering plants show sexual reproduction. A look at the diversity of structures of the inflorescences, flowers, and floral parts shows an amazing range of adaptations to ensure the formation of the end products of sexual reproduction, the fruits and seeds. In this chapter, let us understand the morphology, structure, and processes of sexual reproduction in flowering plants (angiosperms).
1.1 FLOWER – A FASCINATING ORGAN OF ANGIOSPERMS
Human beings have had an intimate relationship with flowers since time immemorial. Flowers are objects of aesthetic,
Born in November, 1904, in Jaipur (Rajasthan), Panchanan Maheshwari rose to become one of the most distinguished botanists not only of India but of the entire world. He moved to Allahabad for higher education, where he obtained his D.Sc. During his college days, he was inspired by Dr W. Dudgeon, an American missionary teacher, to develop an interest in Botany and, especially, morphology. His teacher once expressed that if his student progresses ahead of him, it will give him great satisfaction. These words encouraged Panchanan to enquire what he could do for his teacher in return.
He worked on embryological aspects and popularised the use of embryological characters in taxonomy. He established the Department of Botany, University of Delhi, as an important centre of research in embryology and tissue culture. He also emphasised the need for the initiation of work on the artificial culture of immature embryos. These days, tissue culture has become a landmark in science. His work on test tube fertilisation and intra-ovarian pollination won worldwide acclaim. He was honoured with a fellowship from the Royal Society of London (FRS), the Indian National Science Academy, and several other institutions of excellence. He encouraged general education and made a significant contribution to school education through his leadership in bringing out the very first textbooks of Biology for Higher Secondary Schools published by NCERT in 1964.
CHAPTER 1: Sexual Reproduction in Flowering Plants 2
ornamental, social, religious, and cultural value. They have always been used as symbols for conveying important human feelings, such as love, affection, happiness, grief, mourning, etc. The cultivation of ornamental flowering plants is called floriculture.
To a biologist, flowers are morphological and embryological marvels. We have already read in the chapter “Morphology of Flowering Plants” about the various parts of a typical flower (Fig 1.1). The outermost whorl is the calyx, followed by the corolla. These are accessory whorls as they are not directly involved in the process of sexual reproduction. The essential whorls of the flower include the androecium and the gynoecium, the most important units of sexual reproduction.
TEST YOURSELF
1. What are the end products of sexual reproduction in flowering plants?
(1) Calyx and corolla
(2) Androecium and gynoecium
(3) Flowers
(4) Fruits and seeds
Answer Key
(1) 4
1.2 PRE-FERTILISATION: STRUCTURES AND EVENTS
Much before the actual flower is seen on a plant, the decision that the plant is going to
flower has taken place. Several hormonal and structural changes are initiated, leading to the floral primordium’s differentiation and further development. Inflorescences, which bear the floral buds and then the flowers, are formed. In the flower, the male and female reproductive structures, the androecium and the gynoecium, differentiate and develop. The androecium represents the male reproductive organ and the gynoecium represents the female reproductive organ.
1.2.1 Stamen, Microsporangium, and Pollen Grain
The male reproductive organ, the androecium, consists of a whorl of stamens. Stamen is equivalent to microsporophyll . A typical stamen is differentiated into two parts: a long, thin stalk called the filament and the terminal, generally bilobed structure called the anther (Fig 1.2(a)). The proximal end of the filament is attached to the thalamus or the petal of the flower. The number and length of stamens are variable in flowers of different species.
A typical angiospermic anther is bilobed (dithecous). Each lobe has two microsporangia or pollen sacs. The connective connects the two lobes. The anther is a four-sided (tetragonal) structure consisting of four microsporangia located at the corners, two in each lobe. Thus, there are four microsporangia in a dithecous anther. The microsporangia develop further and become pollen sacs (Fig. 1.2(b)). At maturity, two microsporangia of an anther lobe get united by the dissolution of the partition tissue between them. Mature dithecous anthers are tetrasporangiate bilocular (Fig 1.3). Microsporangia (pollen sacs) extend longitudinally all through the length of an anther and are packed with pollen grains.
In plants, e.g., China rose, lady’s finger, etc. (Malvaceae), anther has only a single anther lobe and two microsporangia
Fig. 1.1 Parts of a typical flower
instead of four. Such anthers are called monothecous anthers or one-lobed anthers. Mature monothecous anthers are bisporangiate
Anther
Filament (stalk)
Pollen grains
Pollen sacs
Filament (stalk)
Line of dehiscence
Sporogenous tissue
1. 3 A young anther changing into mature dehisced anther
Structure of Microsporangium
In a transverse section, a typical microsporangium appears near circular in outline. It is generally surrounded by four types of wall layers. The epidermis, endothecium, middle layers, and the tapetum (Fig. 1.4). The outer three wall layers perform the function of protection and help in the dehiscence of anther to release the pollen.
1.2 (b) Three-dimensional cut section of an anther
Middle layers
Connective
Epidermis
Endothecium
Sporogenous tissue (a) (b)
Tapetum
Epidermis
Endothecium
Middle layers
Microspore mother cells
Tapetum
Fig. 1.4 (a) Transverse section of a young anther; (b)Enlarged view of one microsporangium showing wall layers
Fig. 1.2 (a) A typical stamen
Fig.
Pollen grains
Fig
■ The epidermis is single-layered and helps in protection.
■ Endothecium is the single-layered hypodermis of the anther wall with hygroscopic thickenings of α-cellulosic fibrous bands arising from the inner tangential wall, which help in the dehiscence of the anther.
■ Middle layers consist of 1 to 5 layers. These are consumed by developing microspores.
■ The tapetum is the innermost wall layer providing nourishment to the developing pollen grains. Its cells have dense cytoplasm and more than one nucleus.
Tapetum secretes callase enzyme, which dissolves callose substances and helps in the separation of pollen from tetrads. Tapetum secretes pro-ubisch bodies, which get covered with sporopollenin and increase the thickness of exine. These are called ubisch granules.
Microsporogenesis
When anther is young, a group of compactly arranged homogenous cells, called the sporogenous tissue, occupies the centre of each microsporangium. The formation of microspores or pollen from pollen mother cell is called microsporogenesis. The cells of sporogenous tissue undergo meiotic divisions to form microspore tetrads (Fig. 1.6(a)). As the anthers mature and dehydrate, the microspores dissociate from each other and develop into pollen grains. Inside each microsporangium, several thousands of microspores or pollen grains are formed that are released with the dehiscence of anther.
Pollen Grain
Pollen grain represents the male gametophyte. Each pollen grain or microspore is a unicellular, haploid, oval, or rounded structure. Pollen grains are generally spherical, measuring about
25–50 micrometres in diameter. It has two layered walls, exine and intine (Fig. 1.5) . The outer layer, called exine, is thick, tough, and composed of sporopollenin. Sporopollenin is one of the most resistant organic materials known. It can withstand high temperatures and strong acids and alkalis. No enzyme that degrades sporopollenin is known so far. Pollen grain exine has prominent apertures called germ pores, where sporopollenin is absent. Pollen grains are well preserved as fossils because of the presence of sporopollenin. The exine exhibits a fascinating array of patterns and designs.
The inner layer, called intine, is thin and smooth and is composed of pectocellulose.
Development of Male Gametophyte
The development of the male gametophyte is more or less uniform in all flowering plants. The microspore, or the pollen grain, is the first cell of the male gametophyte. The size of the nucleus increases, and it divides periclinally and mitotically to produce a bigger vegetative cell (tube cell) and a smaller generative cell (Fig. 1.6(b)). The vegetative cell has abundant reserve food and a large irregular-shaped nucleus. The generative cell is spindle-shaped with dense cytoplasm and haploid nucleus. The generative cell floats in the cytoplasm of the vegetative cell. At this stage, the dehiscence of the anther takes place and two-celled pollen grains are released. Pollen grains are shed at two-celled stage in more than 60 per
Germ pore
Generative cell
Tube cell
Nucleus Nucleus
Cytoplasm
Cytoplasm
Fig. 1.5 Structure of pollen grain
cent of angiosperms and in the remaining at three-celled stage (one vegetative cell and two male gametes). After reaching the stigma, the intine grows out through a germ pore into a slender pollen tube. The generative cell divides into two male gametes. The lifespan of male gametophytes is very short as compared to that of the sporophyte.
which came into India as a seed contaminant with imported wheat, has become ubiquitous in occurrence and causes pollen allergy.
Asymmetric spindle
Vegetative cell
Generative cell
Fig. 1.6 (a) Enlarged view of a pollen grain tetrad; (b) stages of a microspore maturing into a pollen grain
Pollen grains of many species cause severe allergies and bronchial afflictions in some people, often leading to chronic respiratory disorders, asthma, bronchitis, etc. It may be mentioned that Parthenium or carrot grass,
Pollen grains are rich in nutrients. It has become a fashion in recent years to use pollen tablets as food supplements. In Western countries, many pollen products in the form of tablets and syrups are available in the market. Pollen consumption has been claimed to increase the performance of athletes and race horses.
The period for which pollen grains remain viable is highly variable and, to some extent, depends on the prevailing temperature and humidity. In some cereals, such as rice and wheat, pollen grains lose viability within 30 minutes of their release. In some members of Rosaceae, Leguminosae, and Solanaceae, they maintain viability for months. It is possible to store pollen grains of many species for years in liquid nitrogen (–196°C). Such stored pollen can be used as pollen banks, similar to seed banks, in crop breeding programmes.
Checkpoint
Q. Which substance is responsible for the sticky nature of the pollen grains in entomophilous plants? Answer:
The outermost oily, thick coating of pollen grains, known as the pollen kitt, is responsible for the sticky nature of pollen grains. It is mainly composed of lipids and carotenoids, which are present, particularly in pollen of entomophilous flowers.
1.2.2 The Pistil, Megasporangium (Ovule), and Embryo Sac
The gynoecium represents the female reproductive part of the flower. The gynoecium may consist of a single pistil (monocarpellary) or more than one pistil (multicarpellary). When there is more than one pistil, the pistils
Vacuoles (a)
1: Sexual Reproduction in Flowering Plants
may be fused (syncarpous, e.g., Hibiscus , Papaver) or free (apocarpous, e.g., Annona, Michelia) (Fig. 1.7). Carpels Stigma Apocarpous in Michelia
Fig. 1.7 (a) A dissected flower of Hibiscus showing pistil (other floral parts have been removed); (b) Multicarpellary, syncarpous pistil of Papaver; (c) A multicarpellary, apocarpous gynoecium of Michelia
Each carpel consists of three parts (Fig. 1.7(a)):
■ Stigma – It i s the terminal end of the style, recipient (landing platform) of the pollen grains, and is generally knob-like and sticky.
■ Style – It is the slender projection of the ovary and it bears the stigma at its terminal end.
■ Ovary – It is the swollen basal part of the pistil, which is single or many-chambered (Fig. 1.7). The ovary contains one (e.g., wheat, paddy, mango, sunflower) or more ovules (e.g., papaya, watermelon, orchid) attached to the placenta. Each ovule contains a large embryo sac at maturity. The ovary develops into a fruit, and ovule develops into a seed after fertilisation.
Structure of Megasporangium
An ovule or megasporangium develops from the placenta in the ovary. It is small, generally has an oval structure, and it consists chiefly of a
central body of tissue, the nucellus, surrounded by one o r two protective envelops called integuments . Each ovule is attached to the placenta by a small stalk called the funiculus. The place of attachment of the stalk with the main body of the ovule is called the hilum (which represents the junction between the ovule and funicle). In an inverted ovule, the funicle fuses with the main body of the ovule, forming a sort of ridge, known as raphe.
The nucellus makes up the main part of the ovule, which is the megasporangium proper. A small opening left at the apex of the integuments is called the micropyle. The cells of nucellus have abundant reserve food material. The posterior end of the ovule, where nucellus, integuments, and funiculus fuse together, is called chalaza (representing the basal part of the ovule).
A large oval structure lying embedded in the nucellus towards the micropylar end is the embryo sac or female gametophyte (Fig. 1.8). This makes the most important part of the mature ovule. It is the site of fertilisation, and later on, it bears the embryo. An ovule generally has one embryo sac formed from a megaspore.
Hilum
Funicle
Micropyle
Micropylar pole
Outer integument
Inner integument
Nucellus
Embryo sac
Chalazal pole
Fig. 1.8 A diagrammatic view of a typical anatropous ovule
Type of ovule
Unique character
1. Orthotropous Erect ovule with micropyle, chalaza, and funiculus lying on a straight line
2. Anatropous Inverted ovule in which micropyle is close to funiculus; raphe is formed between funiculus and ovular body, it is found in 82% angiosperms
3. Hemianatropous Ovular body is at right angles to funiculus (T-shaped).
4. Campylotropous The micropyle is directed towards funiculus.
5. Amphitropous Both ovular body and embryo sac are curved (horse-shoe shaped embryo sac). Micropyle is close to chalaza and nearer to funiculus.
6. Circinotropous The funiculus takes a complete turn around the body of ovule.
Megasporogenesis
The formation of megaspores from the megaspore mother cell (2n) inside the ovule is called megasporogenesis. Ovules (one of the cells of nucellus) generally differentiate into a single megaspore mother cell (MMC) in the micropylar region of the nucellus. It is a large cell containing dense cytoplasm and a prominent nucleus. The MMC undergoes meiotic division, which results in the production of four megaspores (Fig. 1.9(a))
Development of Female Gametophyte
Usually, chalazal megaspore alone remains functional, and the other three degenerate. The functional megaspore develops into the female gametophyte. Formation of a female gametophyte from a single megaspore is termed monosporic type (Fig. 1.9(b), (c)).
Megaspore is the initial cell of the female gametophyte or embryo sac. The nucleus of the functional megaspore divides mitotically to form two nuclei, which move to the opposite
poles. Two more sequential mitotic nuclear divisions result in the formation of the four nucleate and, later, the eight nucleate stages.
These mitotic divisions are free nuclear and are not followed immediately by cell wall formation. After the 8-nucleate stage, cell walls are laid down, leading to the organisation of the typical female gametophyte or embryo sac. Six of the eight nuclei are surrounded by cell walls and organised into cells; the remaining two nuclei, called polar nuclei, are situated below the egg apparatus in the large central cell.
There is a characteristic distribution of the cells within the embryo sac. Three cells are grouped at the micropylar end and constitute the egg apparatus
The egg apparatus, in turn, consists of two synergids and one egg cell. Three cells are at the chalazal end and are called the antipodals. The large central cell has two polar nuclei.
Micropylar end
Nucellus
Micropylar end
Nucellus
Micropylar end
1.9 (a) Parts of the ovule showing a large megaspore mother cell, a dyad and a tetrad of megaspores; (b) 2, 4 and 8 nucleate stages of embryo sac and a mature embryo sac; (c) A diagrammatic representation of the mature embryo sac
Thus, a typical angiospermic embryo sac at maturity is 8-nucleate and 7-celled. It is also called monosporic or Polygonum type, which is the most common type of embryo sac.
Structure of Embryo Sac
A typical embryo sac (Polygonum type) consists of three parts. They are egg apparatus, central cell, and antipodals (Fig. 1.10)
The egg apparatus consists of the larger egg cell or female gamete, and the two lateral ones are called synergids. Synergids are shortlived (one of them degenerates at the time of
the entry of the pollen tube and the second, after the entry of the pollen tube into the embryo sac). The egg cell contains the basal nucleus and upper vacuole, while synergids contain a basal vacuole and an upper nucleus. The synergids have special cellular fingerlike thickenings at the micropylar tip, called filiform apparatus.
The synergids help in the following ways: i) Synergids help in growth of pollen tube towards egg apparatus by secreting chemotropically active substances by filiform apparatus.
Megaspore mother cell
Megaspore dyad
Megaspore tetrad
Chalazal
Fig.
ii) Degenerating synergids provide a seat for the pollen tube discharge in the embryo sac.
The largest central cell consists of two polar nuclei, which fuse to form a single diploid secondary nucleus.
Antipodals are the smallest cells of all and are the vegetative cells of the embryo sac. They degenerate before or after fertilisation.
Chalazal end
Micropylar end
Fig. 1.10 A mature embryo sac
Checkpoint
In a flowering plant, the male and the female gametes are non-motile and brought together for fertilisation by pollination. Flowering plants have evolved an amazing array of adaptations to achieve pollination. They make use of external agents to achieve pollination.
Pollination
Antipodals
Polar nuclei Central cell Egg
Synergids Filiform apparatus
Q. Are there any structures in the human life cycle analogous to plant gametophytes?
Provide an explanation to support your answer.
No, in plants, the haploid (gametophyte) generation is multicellular and originates from spores. However, in the animal life cycle, the haploid phase consists of single-celled gametes (sperm or egg) directly resulting from meiosis, without the involvement of spores.
Answer:
1.2.3 Pollination
Pollination is defined as the process of transfer of pollen grains from anther to the stigma of a flower.
Direct pollination Indirect pollination
In gymnosperms, the pollen grains are transferred to the micropyle of the ovule directly. In angiosperms, the ovules are enclosed in the ovary. The pollination is called indirect pollination because the pollen grains have to first reach the stigma.
Kinds of Pollination
Depending on the source of pollen, pollination can be divided into three types (Fig. 1.11) , as explained below.
Autogamy (Self-pollination)
If the pollen grains are transferred from an anther to the stigma of the same flower, then it is called self-pollination or autogamy.
Complete autogamy is rare in a normal flower that opens and exposes the anthers and stigma. Autogamy in such flowers requires synchrony in pollen release and stigma receptivity. Also, the anther and the stigma should lie close to each other so that self-pollination can occur. Continued selfpollination results in inbreeding depression.
Contrivances or adaptations for selfpollination:
Monocliny (bisexuality) – It means that the flowers are bisexual, e.g., pea.
Homogamy – In homogamy, both the sex organs of a flower mature at the same time (synchrony in pollen release and stigma receptivity). It increases the chances for selfpollination, e.g., pea.
Cleistogamy – In some plants, bisexual flowers are formed, which never open throughout life. These are called cleistogamous flowers, such as Commelina , Viola (common pansy), and Oxalis. All the above plants have two types of flowers. One type of flower is cleistogamous, and the other type is chasmogamous flowers, which are similar to flowers of other species with exposed anthers and stigma. Cleistogamous flowers produce assured seed set even in the absence of pollinators.
In cleistogamous flowers, the anthers and stigma lie close to each other. When anthers dehisce in the flower buds, pollen grains come in contact with the stigma to bring about pollination. Thus, cleistogamous flowers are invariably autogamous, as there is no chance of cross-pollen landing on the stigma.
Bud pollination – This pollination occurs in the bud stage before the opening of flowers e.g., wheat, rice.
Geitonogamy
Geitonogamy is the transfer of pollen grains from the anther to the stigma of another flower of the same plant. Although geitonogamy is functionally cross-pollination involving a pollinating agent, genetically, it is similar to autogamy since the pollen grains come from the same plant.
Xenogamy
In xenogamy, pollen grains are transferred from anther to the stigma of a different plant.
This is the only type of pollination that brings genetically different types of pollen grains to the stigma.
Fig. 1.11 Different kinds of pollination
Agents of Pollination
Plants use abiotic (wind and water) and biotic (animals) agents to achieve pollination. Majority of plants use biotic agents for pollination.
Abiotic Agents
Only a small proportion of plants use abiotic agents. Pollen grains coming in contact with stigma are a chance factor in wind and water pollination. To compensate for this uncertainty and associated loss of pollen grains, the flowers produce enormous amounts of pollen grains compared to the number of ovules available for pollination. Both wind and water-pollinated flowers are not very colourful and do not produce nectar.
Wind pollination (anemophily): Pollination by wind (anemophily) is more common amongst abiotic pollinations. It is nondirectional and the pollen reaching the right stigma is a chance process. Wind pollination is quite common in grasses.
By wind (Anemophily)
Agents of pollination
Abiotic Biotic
By water (Hydrophily)
Characteristics of anemophilous flowers:
■ Flowers are small, inconspicuous, and generally packed in inflorescence. A familiar example is the corn cob – the tassels (bunch of silky hairs) are nothing but stigmas and styles (longest) that wave in the wind to trap pollen grains.
■ Non-essential parts are either absent or reduced.
■ The flowers are colourless, odourless, and nectarless.
■ Pollen grains are small, light, dry, and nonsticky. Winged pollen grains are present in Pinus
■ They often possess well-exposed stamens (so the pollens are easily dispersed into wind currents) (Fig. 1.12).
■ There is a single ovule inside the ovary.
■ Stigma is hairy, feathery, or branched to catch the wind-borne pollen grains.
■ In the case of unisexual flowers, the male flowers are more abundant. In bisexual flowers, the stamens are generally numerous.
By animals (Zoophily)
l By insects (Entomophily)
l By birds (Ornithophily)
l By bats (Chiropterophily)
l By ants and termites (Myrmecophily)
l By snail (Malacophily)
l By snake (Ophiophily)
Fig. 1.12 A wind-pollinated plant showing compact inflorescence and well-exposed stamens
Water pollination (hydrophily): Pollination by water is quite rare in flowering plants and is limited to about 30 genera, mostly monocotyledons. As against this, you would recall that water is a regular mode of transport
1: Sexual Reproduction in Flowering Plants
for the male gametes among the lower plant groups, such as algae, bryophytes, and pteridophytes. It is believed, particularly for some bryophytes and pteridophytes, that their distribution is limited because of the need for water for the transport of male gametes and fertilisation. Some examples of waterpollinated plants are Vallisneria and Hydrilla, which grow in fresh water, and several marine sea grasses such as Zostera . Not all aquatic plants use water for pollination. In a majority of aquatic plants, such as water hyacinth and water lily, the flowers emerge above the level of water and are pollinated by insects or wind, as in most land plants.
Characteristics of hydrophilous plants:
■ Flowers are small and not very colourful.
■ Nectar and odour are absent.
■ Stigma is long and sticky but unwettable.
■ In most water-pollinated species, pollen grains are protected from wetting by a mucilaginous covering.
It is of two types — epihydrophily and hypohydrophily.
Vallisneria exhibits epihydrophily, where pollination will take place on the surface of water. In Vallisneria, the female flower reaches the surface of water by the long stalk and the male flowers or pollen grains are released on to the surface of water. They are carried passively by water currents (Fig 1.13) ; some eventually reach the female flowers and the stigma.
In another group of water-pollinated plants, such as seagrasses, female flowers remain submerged in water, and the pollen grains are released inside the water, i.e., they exhibit hypohydrophily. Pollen grains in many such species are long and ribbon-like. They are carried passively inside the water; some of them reach the stigma and achieve pollination.
Biotic Agents
When animals bring about pollination, it is called zoophily.
The majority of flowering plants use a range of animals as pollinating agents. Bees, butterflies, beetles, wasps, ants, moths, birds, and bats are common pollinating agents.
Among the animals, insects, particularly bees, are the dominant biotic pollinating agents. Larger animals, such as some primates (lemurs), arboreal (tree-dwelling) rodents, or even reptiles (gecko lizard and garden lizard), have also been reported as pollinators in some species.
Generally, in zoophilous plants, flowers are large and attractive, and nectar glands are present. Often, flowers of animal-pollinated plants are specifically adapted for a particular species of animals.
Entomophily: It refers to insect pollination. Insects are the most common pollinators. The most common insect pollinators are moths, flies, butterflies, wasps, bees, and beetles.
Characteristics of entomophilous plants:
■ The majority of insect-pollinated flowers are large, colourful, fragrant, and rich in nectar.
■ When the flowers are small, several flowers are clustered into an inflorescence to make them conspicuous.
Female flower
Male flower Stigma
Fig 1.13 Pollination by water in Vallisneria
■ Animals are attracted to flowers by colour and/or fragrance.
■ The flowers pollinated by flies and beetles secrete foul odours to attract these animals.
■ To sustain animal visits, the flowers have to reward the animals. Nectar and pollen grains are the usual floral rewards. For harvesting the reward(s) from the flower, the animal visitor comes in contact with the anthers and the stigma. The animal’s body gets a coating of pollen grains, which are generally sticky in animal-pollinated flowers. When the animal carrying pollen on its body comes in contact with the stigma, it brings about pollination.
In some species, floral rewards provide safe places to lay eggs; an example is that of the tallest flower of Amorphophallus (the flower itself is about 6 feet in height). A similar relationship exists between a species of moth and the plant Yucca , where both species –moth and the plant – cannot complete their life cycles without each other. The moth deposits its eggs in the locule of the ovary, and the flower, in turn, gets pollinated by the moth. The larvae of the moth come out of the eggs as the seeds start developing.
Many insects may consume pollen or nectar without bringing about pollination. Such floral visitors are referred to as pollen or nectar robbers.
Outbreeding Device (Contrivances for Cross-pollination)
Flowering plants have developed many devices to discourage self-pollination and encourage cross-pollination. Some outbreeding devices are described below.
Dichogamy: In some species, pollen release and stigma receptivity are not synchronised in a bisexual flower.
■ Protandry: Anthers mature earlier than stigma, e.g., sunflower.
■ Protogyny: Gynoecium matures earlier than the anthers, e.g., Datura, Solanum.
Herkogamy: In some species, the anther and stigma are placed at different positions (Hibiscus) or in different directions (Gloriosa) so that the pollen cannot come in contact with the stigma of the same flower. Hence, self-pollination is prevented due to structural barrier.
Heterostyly: In some plants, flowers have two (dimorphic) or three (trimorphic) forms of anthers and stigmas at different levels.
Self-incompatibility: This genetic mechanism prevents self-pollen from fertilising the ovules by inhibiting pollen germination or pollen tube growth in the pistil, e.g., Passiflora, orchids.
Dicliny/unisexuality: The production of unisexual flowers is called dicliny. The plants with unisexual flowers may be monoecious or dioecious. A monoecious plant is one in which male and female organs are found on the same plant but in different flowers (maize, castor). It can prevent autogamy but not geitonogamy.
A dioecious plant is one in which male and female flowers appear on separate plants, e.g., Morus alba (mulberry), Piper betel, Vallisneria, and papaya (Carica). This condition prevents both autogamy and geitonogamy.
Checkpoint
1. Are all offspring of a self-pollinating plant identical?
2. What might account for the evolutionary prevalence of long styles in the majority of flowering plants, considering that shorter styles would facilitate easier access for pollen tubes to reach the embryo sac?
2. Long styles selectively filter out genetically inferior pollen grains incapable of effectively growing long pollen tubes, thereby promoting successful fertilisation with genetically superior pollen.
1. Not necessarily; while self-pollination can lead to offspring that are genetically similar to the parent plant, they may not be completely identical. Self-pollination can result in some genetic variation due to processes such as mutation or genetic recombination during the formation of gametes (sex cells).
Answers:
1.2.4 Pollen–Pistil Interaction
Pollination does not guarantee the transfer of the right type of pollen (compatible pollen of the same species as the stigma). Often, pollen of the wrong type, either from other species or the same plant (if it is self-incompatible), also lands on the stigma. The pistil has the ability to recognise the pollen; whether it is of the right type (compatible) or the wrong type (incompatible). If it is the right type, the pistil accepts the pollen and promotes postpollination events that lead to fertilisation. If the pollen is of the wrong type, the pistil rejects the pollen by preventing pollen germination on the stigma or the pollen tube growth in the style. The ability of the pistil to recognise the pollen, followed by its acceptance or rejection, is the result of a continuous dialogue between the pollen grain and the pistil. This dialogue is mediated by chemical components of the pollen interacting with those of the pistil. It is only in recent years that botanists have identified some of the pollen and pistil components and the interactions leading to the recognition, followed by acceptance or rejection.
As mentioned earlier, following compatible pollination, the pollen grain germinates on the stigma to produce a pollen tube through one of the germ pores. The contents of the pollen
grain move into the pollen tube. The pollen tube grows through the tissues of the stigma and style and reaches the ovary (Fig. 1.14(a)) . You would recall that in some plants, pollen grains are shed at two-celled condition (a vegetative cell and a generative cell). In such plants, the generative cell divides and forms the two male gametes during the growth of pollen tube in the stigma.
In plants that shed pollen in the three-celled condition, pollen tubes carry the two male gametes from the beginning. Pollen tube, after reaching the ovary, enters the ovule through the micropyle and then enters one of the synergids through the filiform apparatus (Fig. 1.14 (b), (c)). Many recent studies have shown that filiform apparatus present at the micropylar part of the synergids guides the entry of pollen tube. All these events — from pollen deposition on the stigma until pollen tubes enter the ovule — are called pollen–pistil interaction. As pointed out earlier, pollen–pistil interaction is a dynamic process involving pollen recognition followed by promotion or inhibition of the pollen. The knowledge gained in this area would help the plant breeder manipulate pollen–pistil interaction, even in incompatible pollinations, to get desired hybrids. The pollen of pea, chickpea, Crotalaria, balsam, and Vinca germinate in 15–30 minutes, if placed in a drop of sugar solution (of about 10%).
Pollen tube
Antipodal
Polar nuclei
Egg cell
Synergid
Fig. 1.14 (a) Longitudinal section of pistil showing path of pollen tube growth
Central cell
Egg nucleus
Plasma membrane
Synergid
Filiform apparatus
Male gametes
Vegetative nucleus
Fig. 1.14 (b) Enlarged view of an egg apparatus showing entry of pollen tube into a synergid
Polar nuclei
Male gametes
Checkpoint
Q. Why does the pollen tube enter the embryo sac only through the micropylar end?
Answer: The synergids containing the filiform apparatus are located at the micropylar end. This filiform apparatus provides chemical signals that are responsible for the exclusive entry of the pollen tube through the micropylar end.
1.2.5 Artificial Hybridisation
Artificial hybridisation is one of the major approaches to crop improvement programme. In such crossing experiments, it is important to ensure that only the desired pollen grains are used for pollination and the stigma is protected from contamination (from unwanted pollen). This is achieved by emasculation and bagging techniques.
Fig. 1.14 (c) Discharge of male gametes into a synergid and the movement of the sperms, one into the egg and the other into the central cell
Entry of Pollen Tube Inside the Ovule
Porogamy: The most common process of entry of pollen tube into the ovule through micropyle is called porogamy.
Chalazogamy: The process of entry of pollen tube into the ovule through chalaza is called chalazogamy.
Mesogamy: The process of entry of pollen tube into the ovule through integuments or funiculus is called mesogamy.
The pollen tube always enters the embryo sac through micropylar end.
If the female parent bears bisexual flowers, the removal of anthers from the flower bud, using a pair of forceps, is referred to as emasculation. Emasculated flowers have to be covered with a bag of suitable size, generally made up of butter paper, to prevent contamination of its stigma with unwanted pollen. This process is called bagging. When the pollen grains collected from the anthers of the male parent are dusted on the stigma, the flowers are rebagged, and the fruits are allowed to develop.
If the female parent produces unisexual flowers, there is no need for emasculation. In that case, the female flower buds are bagged before the flowers open. When the stigma becomes receptive, pollination is carried out using the desired pollen and the flower is rebagged.
TEST YOURSELF
1. Nutritive tissue in anther is (1) perisperm (2) endosperm (3) tapetum (4) nucellus
2. Viability of pollen grains depends on (1) exine
(2) structure of intine
(3) temperature and humidity
(4) pressure and gravity
3. What is the thick walled layer of anther helpful in its dehiscence on its dehydration and subsequent release of pollen?
(1) Epidermis (2) Endothecium
(3) Middle layers (4) Tapetum
4. Number of microspore tetrads formed from 10 pollen mother cells is (1) 40 (2) 40 (3) 30 (4) 10
5. A typical angiospermic anther is where each lobe contains microsporangia.
(1) bilobed, two (2) bilobed, four
(3) monothecous, two (4) single lobed, four
6. What is the ploidy of polar nucleus at the time of embryo sac development?
(1) n (2) 2n
(3) 3n (4) 8n
7. A typical female gametophyte develops from (1) 4 megaspores (2) 3 megaspores (3) 2 megaspores (4) single megaspore
8. Identify the terms associated with the gynoecium.
(1) Stigma, ovule, embryo sac, and placenta
(2) Thalamus, pistil, style, and ovule
(3) Ovule, ovary, embryo sac, and tapetum
(4) Ovule, stamen, ovary, and embryo sac
9. Which of the following pairs is apocarpous?
(1) Anona and Papaver
(2) Hibiscus and Papaver
(3) Anona and Michelia
(4) Hibiscus and Michelia
10. Filiform apparatus is observed in (1) egg (2) antipodals
(3) synergids (4) sperm
11. In which group of plants, water is a regular mode of transport for the male gametes?
(1) Gymnosperms and angiosperms
(2) Bryophytes, pteridophytes, and spermatophytes
(3) Bryophytes, pteridophytes, and gymnosperms
(4) Algae, bryophytes, and pteridophytes
12. Inbreeding depression is due to (1) absence of sexual reproduction
(2) absence of asexual reproduction
(3) continuous cross pollination
(4) continuous self pollination
13. Among the following, the long ribbon-like pollen grains are seen in (1) Zostera
(2) Vallisneria
(3) Water lily
(4) Grasses
14. Which of the following events is not a part of pollen–pistil interaction?
(1) Germination of pollen grain
(2) Growth of pollen tube through style
(3) Entry of pollen tube into the ovule
(4) Fertilisation
15. In pollen–pistil interaction, (1) pollen recognises whether it has fallen on the right stigma or not
(2) ovary of the pistil has the ability to recognise the pollen
(3) pollen is recognised by only style
(4) pollen is recognised by both stigma and style
16. Pollen tube generally enters the ovule through (1) chalaza (2) integument
(3) funicle (4) micropyle
17. In artificial hybridisation, bagging is done (1) prior to emasculation
(2) to prevent the contamination of stigma of female parent with unwanted pollen
(3) to the flowers of male parent to collect pollen
(4) to flowers of both male and female parents to prevent them from microbial infection
18. In the process of artificial hybridisation, removal of anthers from bisexual flowers of female parent is called (1) bagging
(2) emasculation
(3) rebagging
(4) artificial cross pollination
19. Emasculation is not required in flowers having (1) only pistil (unisexual) (2) both pistil and anthers (bisexual)
(3) both pollen and egg (4) homogamy
Answer Key
(1) 3 (2) 3 (3) 2 (4) 4
(5) 1 (6) 1 (7) 4 (8) 1
(9) 3 (10) 3 (11) 4 (12) 4
(13) 1 (14) 4 (15) 4 (16) 4 (17) 2 (18) 2 (19) 1
1.3 DOUBLE FERTILISATION
After entering one of the synergids, the pollen tube releases the two male gametes into the cytoplasm of the synergid.
Syngamy: The fusion of one male gamete with the egg to form a zygote (2n) is called syngamy or generative fertilisation. It was discovered by Strasburger.
Triple fusion: The fusion of the second male gamete with two polar nuclei or secondary nucleus to form a triploid primary endosperm
nucleus (PEN) is known as triple fusion or vegetative fertilisation. The central cell with PEN is called primary endosperm cell (PEC) and develops into endosperm, while zygote develops into embryo.
The simultaneous occurrence of syngamy and triple fusion in the embryo sac of angiosperms is called double fertilisation (Fig. 1.15). Double fertilisation and triple fusion were first reported by S.G. Nawaschin (1898) in Fritillaria and Lilium. It is unique to angiosperms.
1. At which location in the embryo sac is the zygote generally formed?
(1) Chalazal end
(2) Near the hilum
(3) Micropylar end
(4) Funicle
2. Identify the odd one based on ploidy level.
(1) Megaspore mother cell
(2) Nucellus
(3) PEN (angiosperms)
(4) Pollen mother cell
3. What is the product of triple fusion?
(1) Primary endosperm nucleus
(2) Zygote
(3) Embryo
(4) Perisperm
Answer Key
(1) 3 (2) 3 (3) 1
1.4 POST-FERTILISATION: STRUCTURES AND EVENTS
Following double fertilisation, events of endosperm and embryo development and the maturation of ovule(s) into seed(s) and ovary into fruit are collectively termed postfertilisation events.
1.4.1 Endosperm
Endosperm development precedes embryo development. As a product of triple fusion, a triploid structure called primary endosperm nucleus (PEN) is formed, which divides mitotically and forms a mass of nutritive cells called the endosperm. Endosperm accumulates food reserves and functions as the nutritive tissue for the developing embryo. Hence, endosperm development precedes embryo development.
In gymnosperms, the endosperm (female gametophyte) is haploid as it develops from a megaspore. It is a pre-fertilisation tissue.
Types of Endosperm
Depending upon the mode of its formation, angiospermic endosperm can be nuclear endosperm or cellular endosperm.
Nuclear Endosperm
It is the most common type of endosperm found in angiosperms. The primary endosperm nucleus divides repeatedly without wall formation to produce many
free nuclei. The multinucleated cytoplasm undergoes cytokinesis and gives rise to a multicellular tissue (Fig. 1.16), e.g., maize, wheat, rice, sunflower, and Capsella . The number of free nuclei formed before cellularisation varies greatly. In several cases, at maturity, the centripetal wall formation may occur to make the tissue partly cellular. For example, in coconut, the surrounding white kernel, called coconut meat, is the cellular endosperm and the coconut water in the centre is free nuclear endosperm made up of thousands of nuclei.
Cellular Endosperm
Every division of the primary endosperm nucleus is followed by cytokinesis. Therefore, endosperm becomes cellular from the very beginning (Fig. 1.17), e.g., Balsamia, Datura, and Petunia. It is reported in about 72 families of angiosperms (mostly dicots).
Fate of Endosperm
During embryogenesis, the developing embryo draws nutrition from the food stored in the endosperm.
Exalbuminous or non-endospermic seeds: If the developing embryo completely consumes the endosperm, the seed becomes nonendospermic, e.g., gram, pea, groundnut, and bean.
Albuminous or endospermic seeds: If the endosperm is partly consumed by the developing embryo, then the matured seed contains endosperm, e.g., Datura, Castor , coconut, cereals (wheat, maize, barley).
Fig. 1.16 Embryo sac showing the formation of nuclear endosperm
Fig. 1.17 Development of cellular endosperm
1.4.2 Embryo
The embryo develops at the micropylar end of the embryo sac where the zygote is situated. Most zygotes divide only after a certain amount of endosperm is formed. This is an adaptation to provide assured nutrition to the developing embryo. Though the seeds differ greatly, the early stages of embryo development (embryogeny) are similar in both monocotyledons and dicotyledons. The process of development of embryo from the zygote is called embryogenesis or embryogeny.
Embryogeny in Dicots
Let us discuss embryogenesis in dicots (Fig. 1.18)
The first division of the zygote is transverse, resulting in two cells being formed. One cell that lies towards the micropyle is called the basal or suspensor cell. The other cell that lies towards the chalaza is the apical or embryonal cell.
The basal cell (suspensor cell) and embryonal cell divide simultaneously. The embryonal cell is divided by mitotic divisions to give rise to the proembryo and the globular, heart-shaped, and mature embryo.
The suspensor cell is divided by transverse divisions, forming a 6–10 celled long filamentlike structure, which is termed a suspensor.
The main function of the suspensor is to push the developing embryo into a foodladen endosperm to provide nutrition. The micropylar cell of the suspensor swells up. This cell of suspensor is known as haustorial cell.
In Capsella, due to the curved position of the body of the ovule, the embryo becomes curved. This curved position of the embryo is called torpedo (mature embryo). A typical dicot embryo consists of an embryonal axis and two cotyledons.
The axis present between the plumule and the radicle is called the embryonal axis. It is also called tigellum (main embryonal axis). The portion of the embryonal axis above the level of cotyledons is known as epicotyl, which terminates with the plumule or stem tip. The cylindrical portion of the embryonal axis below the level of cotyledons is known as hypocotyl. Hypocotyl terminates in the radicle or root tip. The root cap covers the root tip or radicle (Fig. 1.19).
Both the cotyledons are present at the lateral position of the embryonal axis and the plumule is formed in the terminal position in dicotyledon embryo. This type of development of embryo is known as Crucifer type or onagrad type of development. It is the most common type of embryo development in dicots.
Crucifer type of embryo development is found in Capsella.
Fig. 1.18 Stages in embryo development in a dicot
Fig. 1.19 A typical dicot embryo
Hypocotyl Radicle
Root cap
Embryos of monocotyledons (Fig. 1.20) possess only one cotyledon. In the grass family, the cotyledon is called scutellum, which is situated towards one side (lateral) of the embryonal axis. At its lower end, the embryonal axis has the radical and root cap enclosed in an undifferentiated sheath, called coleorrhiza
The portion of the embryonal axis above the level of attachment of scutellum is the epicotyl. Epicotyl has a shoot apex and a few leaf primordia enclosed in a hollow foliar structure, called the coleoptile (Fig. 1.20).
Scutellum
Coleoptile Shoot apex
Fig. 1.20 Longitudinal section of embryo of grass
1.4.3 Seed
In angiosperms, the seed is the final product of sexual reproduction. It is often described
as a fertilised ovule. Seeds are formed inside fruits. A seed typically consists of seed coat(s), cotyledon(s), and an embryo axis. The cotyledons of the embryo are simple structures, generally thick and swollen due to storage of food reserves (as in legumes).
As already discussed, mature seeds may be albuminous or exalbuminous. Occasionally, in some seeds, such as black pepper and beet, remnants of nucellus are also persistent. This residual, persistent nucellus is the perisperm.
Integuments of ovules harden to form tough protective seed coats (Fig. 1.21(a)) . The micropyle remains as a small pore in the seed coat. This facilitates the entry of oxygen and water into the seed during germination. As the seed matures, its water content is reduced, and seeds become relatively dry (10–15 per cent moisture by mass). The general metabolic activity of the embryo slows down. The embryo may enter a state of inactivity, called dormancy , or, if favourable conditions are available (adequate moisture, oxygen, and suitable temperature), they germinate.
As ovules mature into seeds, the ovary develops into a fruit, i.e., the transformation of ovules into seeds and ovary into fruit proceeds simultaneously. The wall of the ovary develops into the wall of fruit, called pericarp. The fruits may be fleshy, as in guava, orange, mango, etc., or dry, as in groundnut, mustard, etc. Many fruits have evolved mechanisms for dispersal of seeds.
In most plants, by the time the fruit develops from the ovary, other floral parts degenerate and fall off. However, in a few species, such as apple, strawberry, cashew, etc., the thalamus also contributes to fruit formation. Such fruits are called false fruits (Fig. 1.21(b)). Most fruits, however, develop only from the ovary and are called true fruits . Although, in most of the species, fruits are the result of fertilisation, there are a few species
Plumule Cotyledons
Cotyledons
Seed coat
Shoot apical meristem
Hypocotyl root axis
Root tip
Seed coat
Endosperm
Cotyledon
Hypocotyl root axis
Shoot apical meristem
Root tip
Endocarp Mesocarp
in which fruits develop without fertilisation. Such fruits are called parthenocarpic fruits. Banana is one such example. Parthenocarpy can be induced by applying growth hormones. Parthenocarpic fruits are seedless.
Seeds offer several advantages to angiosperms. Some advantages are listed below.
■ Since reproductive processes such as pollination and fertilisation are independent of water, seed formation is more dependable.
■ Seeds have better adaptive strategies for dispersal to new habitats and help the species to colonise in other areas.
■ They have sufficient food reserves; young seedlings are nourished until they are capable of photosynthesis on their own.
■ The hard seed coat protects the young embryo.
Micropyle
Cotyledon
Endosperm
Endosperm
Pericarp
Scutellum
Coleoptile Plumule
Radicle
Coleorrhiza
Thalamus
Thalamus
Achene
Fig. 1.21 (a) Structure of some seeds (b) False fruits of apple and strawberry
■ Being products of sexual reproduction, they generate new genetic combinations, leading to variations.
Seed is the basis of our agriculture. Dehydration and dormancy of mature seeds are crucial for the storage of seeds, which can be used as food throughout the year and also to raise crops in the next season.
Seed Viability
The ability of seeds to retain the power of germination over a period of time is called the viability of seeds. This period varies greatly. In a few species, the seeds lose viability within a few months. Seeds of a large number of species live for several years. There are several records of very old yet viable seeds. The oldest is that of a lupine, Lupinus arcticus, excavated from Arctic Tundra. The seed germinated and flowered after an estimated recorded 10,000 years of dormancy. A recent record of a 2000-year-old viable seed is of the date palm, Phoenix dactylifera , discovered during the archaeological excavation at King Herod’s palace near the Dead Sea. Seed viability is influenced by conditions during storage and non-germination. Excessive dry or damp weather and high temperatures are known to reduce viability of all seeds.
TEST YOURSELF
1. A dicot genus with oily endosperm in its mature seed is
(1) wheat (2) castor
(3) groundnut (4) coconut
2. Number of seeds is equal to the number of fertilised
(1) ovules
(2) ovaries
(3) carpels
(4) antipodals
3. Identify the hollow foliar structure that encloses the shoot apex and a few leaf primordia of epicotyl.
(1) Coleorhiza
(2) Scutellum
(3) Coleoptile
(4) Epiblast
4. The most common type of endosperm development is
(1) helobial type
(2) free nuclear type
(3) cellular type
(4) indirect type
5. Arrange the following stages of embryogeny of dicots in correct progressive sequence.
A. Proembryo
B. Heart-shaped embryo
C. Globular embryo
D. Mature embryo
(1) A → C → B → D
(2) A → B → C → D
(3) C → B → A → D
(4) B → C → A → D
6. As the seed matures, its water content is reduced to
(1) 80–0% moisture by mass
(2) 10–15% moisture by mass
(3) 25–35% moisture by mass
(4) 35–50% moisture by mass
7. Seed viability of date palm is
(1) 2000 years
(2) 1000 years
(3) 5000 years
(4) 100 years
8. If the number of chromosomes in egg cell is 8, then what is the number of chromosomes in endosperm?
(1) 24 (2) 8
(3) 16 (4) 12
9. What is ploidy of perisperm?
(1) n (2) 2n
(3) 3n (4) 4n
10. Micropyle exists in
(1) ovule and ovary
(2) seed and embryo
(3) seed and ovule
(4) fruit and inflorescence
Answer Key
(1) 2 (2) 1 (3) 3 (4) 2
(5) 1 (6) 2 (7) 1 (8) 1
(9) 2 (10) 3
1.5 APOMIXIS AND POLYEMBRYONY
Although seeds, in general, are the products of fertilisation, a few flowering plants, such as some species of Asteraceae and grasses, have evolved a special mechanism to produce seeds without fertilisation, called apomixis
Apomixis is a form of asexual reproduction that mimics sexual reproduction. There are several ways of development of apomictic seeds. In some species, the diploid egg cell is formed without reduction division and develops into the embryo without fertilisation. More often, as in many Citrus and mango varieties, some of the nucellar cells surrounding the embryo sac start dividing, protruding into the embryo sac, and developing into the embryos. In such species, each ovule contains many embryos. The occurrence of more than one embryo in a seed is referred to as polyembryony.
Hybrid varieties of several of our food and vegetable crops are being extensively cultivated. The cultivation of hybrids has tremendously increased productivity. One of the problems of hybrids is that hybrid seeds have to be produced every year. If the seeds collected from hybrids are sown, the plants in the progeny will segregate and do not maintain
hybrid characters. Production of hybrid seeds is costly, and hence, the cost of hybrid seeds becomess too expensive for the farmers. If these hybrids are made into apomicts, there is no segregation of characters in the hybrid progeny. Then, the farmers can keep on using the hybrid seeds to raise new crops year after year, and he does not have to buy hybrid seeds every year. Because of the importance of apomixis in the hybrid seed industry, active research is going on in many laboratories around the world to understand the genetics of apomixis and to transfer apomictic genes into hybrid varieties.
Checkpoint
Q. What is the genetic composition of embryos produced through apomixis? Answer: The genetic composition of embryos produced through apomixis is same as maternal parent.
TEST YOURSELF
1. Nucellar polyembryony is commonly seen in which of these plants?
(1) Apple and mango
(2) Pepper and citrus
(3) Mango and citrus
(4) Apple and sugarbeet
2. Occurrence of more than one embryo is called
(1) polyembryony
(2) embryony
(3) parthenogenesis
(4) fertilisation
3. Seed production without fertilisation is called
(1) parthenocarpy
(2) apospory
(3) apomixis
(4) polyembryony
4. Which of the following can be expected if scientists succeed in introducing apomictic gene into hybrid varieties of crops?
(1) Polyembryony will be seen and each seed will produce many plantlets.
(2) Seeds of hybrid plants will show longer dormancy.
(3) Farmers can keep on using the seeds produced by the hybrids to raise new crop year after year.
(4) There will be segregation of the desired characters only in the progeny.
CHAPTER REVIEW
Pre-Fertilisation: Structures and Events
Stamen, Microsporangium, and Pollen Grain
■ A typical stamen consists of two parts: the slender stalk, known as the filament, and the terminal bilobed structure called the anther.
■ The proximal end of the filament is attached to either the thalamus or the petal of the flower.
■ The transverse section of an anther shows a distinct bilobed structure, with each lobe consisting of two microsporangia located at the corners, totalling four microsporangia in the entire anther.
■ The microsporangia develop into pollen sacs, extending longitudinally along the length of the anther, and are packed with pollen grains.
■ The structure of a microsporangium is typically near-circular in outline when viewed in a transverse section.
■ It is surrounded by four layers of walls: the epidermis, endothecium, middle layers, and tapetum.
■ The epidermis, endothecium, and middle layers primarily provide protection and aid in the dehiscence of the anther for pollen release.
5. What is common between vegetative reproduction and apomixis?
(1) Both are applicable to only dicot plants.
(2) Both bypass the flowering phase.
(3) Both occur round the year.
(4) Both produce progeny identical to the parent.
Answer Key
(1) 3 (2) 1 (3) 3 (4) 3
(5) 4
■ The innermost layer, the tapetum, nourishes the developing pollen grains. It is characterised by dense cytoplasm and usually more than one nucleus per cell.
■ Tapetal cells can become binucleate through various mechanisms, such as endomitosis or karyokinesis without cytokinesis.
■ In young anthers, a group of compactly arranged homogenous cells, called sporogenous tissue, occupies the centre of each microsporangium.
■ Microsporogenesis is the process through which microspores are formed from a pollen mother cell (PMC) via meiosis. Microspores are arranged in clusters of four cells known as microspore tetrads.
■ As anthers mature and dehydrate, microspores dissociate from each other and develop into pollen grains. Several thousand pollen grains are formed within each microsporangium and are released upon anther dehiscence.
■ Pollen grains serve as male gametophytes.
■ Pollen grains typically have a spherical shape with a diameter ranging from 25 to 50 micrometres and a prominent twolayered wall.
■ The outer layer, called the exine, is composed of sporopollenin, a highly resistant organic material that protects pollen grains and makes them as wellpreserved as fossils. Germ pores in the exine facilitate pollen tube formation during pollination.
■ The inner wall of the pollen grain, called the intine, is a thin layer made of cellulose and pectin.
■ Mature pollen grains contain two cells: the vegetative cell, which is larger and contains abundant food reserves, and the generative cell, which is smaller and floats within the cytoplasm of the vegetative cell.
■ In some angiosperms, pollen grains are shed with two cells (2-celled stage), while in others, the generative cell divides mitotically to produce two male gametes before shedding (3-celled stage).
■ Pollen grains of many species can cause allergies and respiratory disorders in susceptible individuals.
■ Pollen grains are rich in nutrients and are used as food supplements in some cultures, with claims of enhancing athletic performance and health.
■ The viability of pollen grains varies widely, depending on factors such as temperature and humidity. While some grains lose viability within minutes of release, others can remain viable for months.
■ Pollen grains can be stored for extended periods in seed banks by cryopreservation in liquid nitrogen (–196°C), enabling their use in crop breeding programs.
The Pistil, Megasporangium (Ovule), and Embryo Sac
■ The gynoecium, or female reproductive part of the flower, may consist of a single pistil (monocarpellary) or more than one pistil (multicarpellary), which can be fused (syncarpous) or free (apocarpous).
■ Each pistil comprises three parts: the stigma, style, and ovary. The stigma serves as a landing platform for pollen grains, the style is an elongated slender part beneath the stigma, and the basal bulged part is the ovary, which contains the ovarian cavity (locule) and the placenta.
■ The ovule is a small structure attached to the placenta by a stalk called the funicle, with the hilum representing the junction between the ovule and the funicle. Each ovule has one or two protective envelopes called integuments, encircling the nucellus, except at the tip, where the micropyle is located.
■ Enclosed within the integuments is the nucellus, containing abundant reserve food materials, and the embryo sac or female gametophyte, typically formed from a single megaspore.
■ Megasporogenesis involves the formation of megaspores from the megaspore mother cell (MMC) through meiotic division, resulting in the production of four megaspores.
■ In most flowering plants, only one megaspore remains functional, developing into the female gametophyte (embryo sac) through monosporic development.
■ The nucleus of the functional megaspore undergoes three rounds of mitosis (freenuclear divisions) followed by nuclear rearrangement and cell wall formation.
■ This results in formation of a typical female gametophyte or embryo sac, which is a 7-celled and 8-nucleated structure.
■ The embryo sac has a characteristic distribution of cells, with three cells grouped at the micropylar end, forming the egg apparatus (two synergids and one egg cell), three cells at the chalazal end, called the antipodals, and the large central cell containing two polar nuclei.
Pollination
■ Pollination is the mechanism by which non-motile male and female gametes in flowering plants are brought together for fertilisation.
■ There are three types of pollination:
• Autogamy: Pollination occurs when pollen grains are transferred from the anther to the stigma of the same flower.
• Geitonogamy: Pollination involves the transfer of pollen grains from the anther to the stigma of another flower on the same plant.
• Xenogamy: Pollination occurs when pollen grains from the anther of one plant are transferred to the stigma of a different plant.
■ Plants utilise various agents for pollination, including abiotic agents, such as wind and water, and biotic agents, such as animals.
■ Wind-pollinated flowers typically have light, non-sticky pollen grains and wellexposed stamens, while water-pollination is found in a limited number of genera, mostly monocotyledons.
■ Animal-pollinated flowers are often large, colourful, and fragrant, attracting animals such as bees, butterflies, flies, beetles, birds, and bats. These flowers provide rewards like nectar and pollen grains to attract pollinators.
■ Flowers have evolved various mechanisms to prevent self-pollination and encourage cross-pollination, including asynchronous pollen release and stigma receptivity, physical separation of anther and stigma, self-incompatibility mechanisms, and the production of unisexual flowers.
■ Following compatible pollination, the pollen grain germinates on the stigma to produce a pollen tube, facilitating the
transfer of male gametes to the ovule for fertilisation.
■ Pollen–pistil interaction is a dynamic process of pollen recognition by the pistil, leading to either acceptance or rejection of the pollen grain based on its compatibility.
■ Plant breeders use techniques such as emasculation and bagging to control pollination and prevent contamination in artificial hybridisation experiments, ensuring desired crosses for crop improvement.
Double Fertilisation
■ After the pollen tube enters a synergid, it releases two male gametes.
■ One male gamete fuses with the egg cell, forming a diploid zygote (syngamy).
■ The other male gamete fuses with two polar nuclei, forming a triploid primary endosperm nucleus (triple fusion).
■ Fusion with two polar nuclei with the male gamete is termed triple fusion, involving three haploid nuclei.
■ Double fertilisation refers to syngamy and triple fusion that occur within the embryo sac.
■ The central cell becomes the primary endosperm cell (PEC), developing into the endosperm. The zygote develops into an embryo.
Post-Fertilisation: Structures and Events
■ Endosperm development precedes embryo development to provide nutrition to the developing embryo.
■ The primary endosperm cell undergoes repeated divisions to form a triploid endosperm tissue filled with reserve food materials.
■ In free-nuclear endosperm development, the PEN gives rise to free nuclei before cellularisation.
■ The embryo may completely consume the endosperm before seed maturation, or the endosperm can persist in the mature seed.
■ Embryo development begins at the micropylar end of the embryo sac, where the zygote is located.
■ Zygotes typically divide only after a certain amount of endosperm is formed to ensure nutrition.
■ Embryogeny starts with the formation of the proembryo, followed by the globular, heart-shaped, and mature embryo stages.
■ A typical dicotyledonous embryo consists of an embryonal axis and two cotyledons.
■ Monocotyledonous embryos possess an embryonal axis and a single cotyledon. In the grass family the cotyledons called scutellum.
■ Seeds in angiosperms are the final products of sexual reproduction, formed inside fruits.
■ A seed typically consists of seed coat(s), cotyledon(s), and an embryo axis.
■ Cotyledons are simple structures, often thick and swollen due to the storage of food reserves.
■ Seeds may be non-albuminous (completely consumed endosperm) or albuminous (retain part of endosperm).
■ Integuments of ovules harden into tough protective seed coats, with the micropyle remaining as a seed pore. It facilitates entry of water and oxygen during seed germination.
■ As the seed matures its water content is reduced and becomes relatively dry. The seed enters a state of dormancy until the on set of favourable conditions.
■ Ovary develops into a fruit simultaneously with ovules maturing into seeds.
■ Fruits may be fleshy or dry, and many fruits have mechanisms for seed dispersal.
■ Some fruits develop from structures other than the ovary and are called false fruits,
while those developing solely from the ovary are true fruits.
■ Fruits developed without fertilisation are parthenocarpic, e.g., banana. Parthenocarpy can be induced by growth hormones.
■ Seeds offer advantages like independence from water for reproductive processes, adaptive strategies for dispersal, nourishment of seedlings, and genetic variation. They are crucial for agriculture.
■ Dehydration and dormancy of mature seeds enable their storage and use as food or for raising crops in subsequent seasons.
■ The viability of seeds varies greatly, with some species remaining alive for several years or even hundreds of years, as evidenced by records of very old yet viable seeds like Lupinus arcticus and Phoenix dactylifera
Apomixis and Polyembryony
■ Apomixis in flowering plants is a form of asexual reproduction mimicking sexual reproduction.
■ Apomictic seeds develop without fertilisation, often through mechanisms like the formation of diploid egg cells without reduction division or the division of nucellar cells.
■ Apomictic embryos are genetically identical and can be considered clones.
■ Apomixis is particularly advantageous in agriculture for maintaining hybrid characteristics without the need to develop hybrid seeds every year.
■ Active research is ongoing globally to understand the genetics of apomixis and transfer apomictic genes into hybrid varieties.
■ In some species, multiple embryos develop within each ovule. This condition is known as polyembryony.
Exercises
NEET DRILL
Flower – A Fascinating Organ of Angiosperms
1. Choose the features of flowers that aid in sexual reproduction.
A. Scent
B. Bright colours
C. Floral rewards
D. Nectaries
(1) A and B only (2) A, B and C only
(3) A, B, C and D (4) C and D only
2. Choose the correct statement.
(1) All the flowers are brightly coloured and attractive.
(2) Flowers are usually involved in asexual or vegetative reproduction.
(3) Every flower has androecium and gynoecium.
(4) Some flowers are complete flowers and some are incomplete.
3. Floriculture refers to
(1) study of flowers
(2) study of flowering plants
(3) study of cultivation of ornamental flowering plants
(4) study of development of flowers
Pre-fertilisation: Structures and Events
Stamen, Microsporangium and Pollen Grain
4. Pollen stored in
(1) liquid oxygen at –196°C
(2) liquid nitrogen at –196°C
(3) liquid oxygen at 196°C
(4) liquid nitrogen at 196°C
5. Arrange the following layers of anther wall from outside to inside.
I. Tapetum
II. Endothecium
III. Epidermis
IV. Middle layers
(1) IV, III, II, I (2) III, II, IV, I
(3) II, IV, III, I (4) II, III, I, IV
6. Dehiscence of anther is facilitated by A. epidermis
B. endothecium
C. middle layer
(1) A and B only (2) B and C only
(3) A and C only (4) A, B and C
7. Ploidy of cells of tetrad of microspores is
(1) 4n (2) 3n
(3) n (4) 2n
8. Which of the following process is shown by the anther of a stamen?
(1) Development of embryo sac
(2) Formation of megaspores
(3) Formation of microspores
(4) Development of embryo
9. Pollen grain represents (1) female gametophyte
(2) male gametophyte
(3) male gamete
(4) female gamete
10. A mature pollen grain
a) contains a bigger generative cell and smaller vegetative cell
b) contains exine and intine
c) lacks germ pores
Choose the incorrect one(s) w.r.t a typical angiospermic plant.
(1) a and b (2) b only
(3) a and c (4) c only
11. Carrot grass (Parthenium) came into India as a contaminant along with imported (1) paddy (2) maize
(3) barley (4) wheat
12. Identify the correct statement.
(1) In over 70 percent of angiosperms, pollen grains all shed at 2-celled stage.
(2) In 50% species of angiosperms, pollination occurs at 3-celled stage of pollen grain.
(3) Intine of pollen grain is made up of cellulose and lignin.
(4) Pollen grains of a many species cause severe allergies and bronchial afflictions in some people.
13. In young anther, central region of microsporangium is occupied by
(1) pollen grains
(2) archesporium
(3) sporogenous tissue
(4) microspores
14. A typical angiospermic anther is (1) monothecous (2) tetrathecous
(3) dithecous (4) trithecous
The Pistil, Megasporangium (ovule) and Embryo sac
15. Bulged basal part of pistil is (1) stigma (2) style
(3) ovary (4) stamen
16. The number of ovules in an ovary may be many in which of the following pair of plants?
(1) Mango and wheat
(2) Paddy and wheat
(3) Papaya and watermelon
(4) Orchids and mango
17. The number of ovules in an ovary may be variable. It can be one ovule in a ovary, in which of the following pair of plants?
(1) Mango and wheat
(2) Papaya and orchids
(3) Watermelon and orchids
(4) Paddy and papaya
18. What is the three celled structure with gamete as one of the cell in female gametophyte of flowering plant?
(1) Antipodals
(2) Primary endosperm cell
(3) Egg apparatus
(4) Tapetum
19. Monosporic embryo sac
(1) is formed after 1 mitosis and 3 meiosis
(2) develops from single megaspore
(3) is seven nucleate and eight celled (4) has 3 egg cells
Pollination, Pollen-Pistil Interaction, and Artificial Hybridisation
20. A dioecious flowering plant prevents both (1) autogamy and xenogamy
(2) autogamy and geitonogamy
(3) geitonogamy and xenogamy
(4) cleistogamy and xenogamy
21. Plants which produce two types of flowers are
(a) Viola
(b) Oxalis
(c) Commelina
(1) a only
(2) a and c only
(3) b and c only
(4) a, b and c
22. What type of pollination is primarily prevented in castor plant, which is monoecious ? (unisexual male and female flowers on the same plant)
(1) Autogamy and geitonogamy
(2) Only geitonogamy
(3) Only xenogamy
(4) Only autogamy
23. The type of pollination involving the transfer of pollen grains from anther to the stigma of the same flower is known as
(1) geitonogamy (2) xenogamy
(3) autogamy (4) apogamy
24. What is the function of tassels in the corn cob?
(1) To protect seeds
(2) To attract insects
(3) To trap pollen grains
(4) To disperse pollen grains
25. Water pollination
A. is rare in flowering plants
B. is limited to 30 genera
C. takes place mostly in monocotyledons
(1) A and B only
(2) B and C only
(3) A and C only
(4) A,B and C
26. Which of the following is correct with reference to animal pollinated plants?
(a) Butterflies, flies, beetles, wasps, ants, moths and bats are common pollinating agents.
(b) Rodents, lizards and primates are also pollinators in some species.
(c) Animal pollinated plants are specifically adapted for particular species.
(1) a only (2) a and c only
(3) b and c only (4) a, b and c
27. Read the following statements and pick the incorrect one.
(1) The pollinating agent in the majority of hydrophytes are insects, as flowers are aerial in most of them.
(2) Numerous ovules inside an ovary and sticky pollen are the characters observed in wind pollinated flowers.
(3) Vallisneria is a fresh water plant with epihydrophylly, whereas Hydrilla is a fresh water plant with hypohydrophylly.
(4) Zostera (sea grass)is a marine plant with ribbon like pollen and exhibits hypohydrophylly.
28. In an artificial hybridisation programme in date palm, which of the following steps would not be relevant?
(1) Emasculation
(2) Bagging of female flower
(3) Collection of pollen
(4) Dusting of pollen on stigma
29. To overcome incompatible pollination so as to get desired hybrids, a plant breeder must have the knowledge of ______
(1) pollen-nucellar interaction
(2) pollen-egg interaction
(3) pollen-pistil interaction
(4) pollen-embryo sac interaction
Double Fertilisation
30. Female plant is octaploid and male plant is tetraploid. Identify the ploidy of zygote.
(1) hexaploid
(2) tetraploid
(3) octaploid
(4) pentaploid
31. How many nuclei participate in syngamy, triple fusion and double fertilisation respectively?
(1) 2, 3 and 5
(2) 3, 2 and 5
(3) 1, 2 and 5
(4) 2, 2 and 5
Post-Fertilisation: Structures and Events
32. The seeds of rice and wheat are
(a) endospermic
(b) non-endospermic
(c) perispermic
(1) a only (2) b only
(3) a and b (4) c only
33. The morphological nature of the edible part of coconut is
(1) cotyledon (2) endosperm
(3) pericarp (4) perisperm
34. What is true about parthenocarpic fruit?
(a) They are seedless fruits.
(b) Banana is an example of parthenocarpic fruit.
(c) It can be induced by growth hormones.
(1) a only (2) a and b only
(3) a and c only (4) a, b and c
FURTHER EXPLORATION
1. Horse shoe shaped embryosac/nucellus is characteristic of (1) orthotropous ovule
(2) anatropous ovule
(3) amphitropous ovule
(4) campylotropous ovule
2. Pollination by snakes is referred to as (1) anemophily (2) entomophily
(3) malacophily (4) ophiophily
3. In which one of the following, achene fruits are formed?
(1) Apple (2) Mango
MATCHING TYPE QUESTIONS
1. Match Column-I with Column-II.
Column-I Column-II
(A) Cleistogamy (I) Inter-plant pollination
(B) Chasmogamy (II) Intraplant but interflower pollination
(C) Geitonogamy (III) Pollination in opened flowers
Apomixis and Polyembryony
35. Apomixis and cleistogamy are similar in A) mode of reproduction B) showing assured seed set C) not showing the requirement of a pollinator
(1) A, B and C
(2) A and B only
(3) B and C only
(4) A and C only
(3) Strawberry (4) Coconut
4. The anther in Capsella is (1) monolobed and monosporangiate (2) bilobed and bisporangiate (3) bilobed and tetrasporangiate (4) monolobed and bisporangiate
5. Apomixis term was coined by (1) Wrinkler
(2) Kary Mullis
(3) Leeuwenhoek (4) Strasburger
(D) Xenogamy (IV) Pollination in closed flowers
Select the correct option.
(A) (B) (C) (D)
(1) IV III II I
(2) III IV I II
(3) IV III I II
(4) IV I II III
2. Match Column-I with Column-II.
Column-I Column-II
(A) Dry fruit (I) Banana
(B) Fleshy fruit (II) Mustard
(C) False fruit (III) Orange
(D) Parthenocarpic fruit (IV) Strawberry
Select the correct option.
(A) (B) (C) (D)
(1) II III IV I
(2) II IV I III
(3) III II IV I
(4) II I III IV
3. Match Column-I with Column-II.
Column-I Column-II
(A) Pollen viability of rice (I) 10,000 years
(B) Pollen viability of some members of Solanaceae family (II) 2000 years
(C) Seed viability of Lupinus arcticus (III) 30 minutes
(D) Seed viability of Phoenix dactylifera (IV) Few months
Select the correct option.
(A) (B) (C) (D)
(1) II IV I III
(2) III IV I II
(3) III I IV II
(4) III II I IV
4. Match Column-I with Column-II.
Column-I Column-II
(A) Germ pore (I) Organic material
(B) Sporopollenin (II) Food supplement
(C) Pollen tablet (III) Emergence of pollen tube
(D) Pollen bank (IV) Crop breeding programmes
Select the correct option.
(A) (B) (C) (D)
(1) IV II I III
(2) III I II IV
(3) III II I IV
(4) IV I II III
5. Match Column-I with Column-II.
Column-I Column-II
(A) Yucca (I) Perispermic seeds
(B) Water hyacinth (II) More than 100 years of seed dormancy
(C) Lupin (III) Symbiotic pollination
(D) Beet (IV) Pollinated by insects
Select the correct option.
(A) (B) (C) (D)
(1) I II IV III
(2) III IV II I
(3) II III I IV
(4) IV III I II
6. Match Column-I with Column-II.
Column-I
Column-II
(A) Bilobed anther (I) Tapetum
(B) Single lobed anther (II) Four microsporangia
(C) Innermost wall layer of anther (III) Two microsporangia
(D) Central region of young anther (IV) Sporogenous tissue
Select the correct option.
(A) (B) (C) (D)
(1) IV III I II
(2) I II IV III
(3) II III I IV
(4) I IV III II
7. Match Column-I with Column-II.
Column-I
Column-II
(A) Egg apparatus (I) Two nuclei
(B) Single antipodal cell (II) Single nucleus
(C) Central cell before fertilisation (III) Three nuclei
(D) Tapetum (IV) Multi nucleate
Select the correct option.
(A) (B) (C) (D)
(1) I III II IV
(2) II I III IV
(3) IV III I II
(4) III II I IV
8. Match Column-I with Column-II.
Column-I
Column-II
(A) Wind pollination (I) Beetles
(B) Water pollination (II) Packed inflorescence
(C) Foul odoured flowers (III) Floral rewards
(D) Nectar and pollen (IV) Very few lower plants
Select the correct option.
(A) (B) (C) (D)
(1) I III II IV
(2) II I III IV
(3) IV I III II
(4) II IV I III
9. Match Column-I with Column-II.
Column-I Column-II
(A) Apple fruit (I) Spindle shaped
(B) Generative cell (II) Thalamus
(C) Typical anther (III) Nearly circular
(D) Microsporangia (IV) Tetragonal
Select the correct option.
(A) (B) (C) (D)
(1) I III II IV
(2) IV I III II
(3) II I IV III
(4) III II I IV
10. Match Column-I with Column-II.
Column-I Column-II
(A) Yucca (I) Water pollination
(B) Sunflower (II) Wind pollination
(C) Miaze (III) Apomixis
(D) Zostera (IV) Moth
Select the correct option.
(A) (B) (C) (D)
(1) I III IV II
(2) IV III II I
(3) III I II IV
(4) II IV III I
STATEMENT TYPE QUESTIONS
Each question has two statements: statement I (S-I) and statement II (S-II). Mark the correct answer as
(1) if both statement I and statement II are correct,
(2) if both statement I and statement II are incorrect,
(3) if statement I is correct but statement II is incorrect,
(4) if statement I is incorrect but statement II is correct.
1. S-I : During the formation of the embryo sac, cell wall is formed immediately at two nucleated stage before further nuclear division.
S-II : Four cells are grouped together at the chalazal end during the embryo sac formation.
2. S-I : In most water pollinated species, pollen grains are not covered by a mucilaginous covering.
S-II : Wind and water pollinated flowers do not produce nectar.
3. S-I : Flowering plants have developed many outbreeding devices to discourage self pollination and to encourage crosspollination.
S-II : Continued self-pollination result in inbreeding depression.
4. S-I : Several hormonal and structural changes take place for further development of the floral primordium.
ASSERTION AND REASON QUESTIONS
In each of the following questions, a statement of Assertion (A) is given, followed by a corresponding statement of Reason (R). Mark the correct answer as
(1) if both (A) and (R) are true and (R) is the correct explanation of (A),
S-II : Inflorescence bear flowers and then flower buds are formed.
5. S-I : The number of free nuclei formed before cellularisation during endosperm formation is fixed among various species.
S-II : Endosperm is completely consumed before seed maturation in castor.
6. S-I : The early stages of embryo development is different in monocots and dicots.
S-II : The zygote first gives rise to proembryo and then globular embryo.
7. S-I : Micropyle facilitates the entry of oxygen and water into the seed during germination.
S-II : During unfavourable conditions, seed may enter into inactive state called dormancy.
8. S-I : Seeds have better adaptive strategies for dispersal to new habitats.
S-II : Orobanche and Striga are parasitic plants.
9. S-I : Seed is the basis of our agriculture.
S-II : Dehydration and dormancy of mature seeds promotes the usage of seeds in agriculture for next season.
10. S-I : Pollen sacs extend horizontally all along the length of a typical anther.
S-II : The microsporangia develop further and become pollen sacs.
(2) if both (A) and (R) are true but (R) is not the correct explanation of (A),
(3) if (A) is true but (R) is false,
(4) if both (A) and (R) are false.
1. (A) : An angiospermous flower represents
the modified condensed shoot which performs the function of sexual reproduction.
(R) : Flowers contain reproductive structures called petals and sepals which participate in sexual reproduction.
2. (A) : Pollen grains can withstand the influence of high temperatures, strong acids and alkalies.
(R) : Pollen grains have an inner wall layer made of cellulose and pectin.
3. (A) : Cleistogamous flowers are invariably autogamous.
(R) : Cleistogamous flowers do not open at all, and anthers and stigma lie close to each other in them.
4. (A) : In some flowers male and female sex organs mature at different times.
(R) : This is a safeguard mechanism against cross-pollination.
5. (A) : Insect-pollinated plants produce less pollen when compared to windpollinated plants.
BRAIN TEASERS
1. Arrange the following structures from largest to smallest, assuming that they belong to two generations of the same angiosperm.
(1) Ovary
(2) Ovule
(3) Egg
(4) Gynoecium
(5) Embryo sac
(1) 4 → 2 → 1 → 5 → 3
(2) 5 → 4 → 3 → 1 → 2
(3) 5 → 1 → 4 → 2 → 3
(4) 4 → 1 → 2 → 5 → 3
2. What does the practice of detasseling corn in the corn belt states, where unwanted male flowers are removed to ensure pollination of female flowers by desired pollen for hybrid
(R) : The wastage of pollen grain is reduced to the minimum in insect-pollinated plants because of directional pollination.
6. (A) : Double fertilisation involves two nuclear fusions in angiosperms.
(R) : Sygamy and triple fusion occur simultaneously in angiosperms.
7. (A) : In maize, autogamy is prevented but not geitonogamy.
(R) : In maize, bisexual flowers are present.
8. (A) : Apomictic embryos are diploid.
(R) : Meiotic division does not take place during the formation of apomictic embryos.
9. (A) : In apomixis, plants of new genetic variations are not produced.
(R) : In apomixis, reductional division takes place.
10. (A) : Active research is going on in many laboratories around the world to understand the genetics of apomixis.
(R) : There is an importance of apomixis in the hybrid seed industry.
corn, indicate about the flowers of corn?
(1) Perfect and the plant is dioecious
(2) Perfect, and the plant is monoecious
(3) Imperfect and the plant is dioecious
(4) Imperfect and the plant is monoecious
3. What would happen if a researcher exposes pollen grains to two stains developed for seed plants, one staining sporophyte tissue blue and the other staining gametophyte tissue red, and then removes the excess stain?
(1) The pollen grains will be pure red.
(2) The pollen grains will be pure blue.
(3) The pollen grains will have red interiors and blue exteriors.
(4) The pollen grains will have blue interiors and red exteriors.
4. What is the minimum number of pollen grains needed to form 50 mature seeds if an ovary contains 50 ovules?
(1) 25 (2) 50
(3) 100 (4) 500
5. What do the beige, petal-less flowers that emerge before the leaves in spring and the dioecious nature of cottonwood, aspen, and willow trees suggest about these trees?
(1) Their insect pollinators are specialists.
(2) Early emerging insects are probably the pollinators.
FLASHBACK (Previous NEET Questions)
1. Identify the correct description about the given figure. (2024–I)
(3) Wind-pollinated plant inflorescence showing flowers with well exposed stamens
(4) Water pollinated flowers showing stamens with mucilaginous covering
2. In angiosperm, the haploid, diploid and triploid structures of fertilised embryo sac sequentially are (2023)
(1) synergids, antipodals and polar nuclei
(2) synergids, primary endosperm nucleus and zygote
(3) antipodals, synergids, and primary endosperm nucleus
(3) Their pollen is dispersed by wind.
(4) The trees are self-pollinating.
6. While observing a flower in your garden, you notice carpels with exceptionally long styles and stamens with notably short filaments. This plant is most likely to reproduce by ________.
(1) cross-pollination
(2) selfing
(3) asexual reproduction
(4) vegetative reproduction
(4) synergids, zygote and primary endosperm nucleus
3. Given below are two statements. (2022) Statement I : Cleistogamous flowers are invariably autogamous
Statement II : Cleistogamy is disadvantageous as there is no chance for cross pollination
In the light of the above statements, choose the correct answer from the options given below.
(1) Both statement I and statement II are incorrect
(2) Statement I is correct but statement II is incorrect
(3) Statement I is incorrect but statement II is correct
(4) Both statement I and statement II are correct
4. In some member of which of the following pairs of families, pollen grains retain their viability for months after release? (2021)
(1) Rosaceae; leguminosae
(2) Poaceae; rosaceae
(3) Poaceae; leguminosae
(4) Poaceae; solanaceae
5. In some plants thalamus contributes to fruit formation. Such fruits are termed as (2020-II)
(1) parthenocarpic fruit
(2) false fruits
(3) aggregate fruits
(4) true fruits
6. What is the fate of the male gametes discharged in the synergid? (2019)
(1) One fuses with the egg and other fuses with central cell nuclei.
(2) One fuses with the egg, other(s) degenerates in the synergid.
(3) All fuse with the egg.
(4) One fuses with the egg, other(s) fuse(s) with synergid nucleus.
7. Which of the following has proved helpful in preserving pollen as fossils? (2018)
(1) Pollen kitt (2) Cellulosic intine
(3) Oil content (4) Sporopollenin
8. Functional megaspore in an angiosperm develops into an (2017)
(1) endosperm (2) embryo sac
(3) embryo (4) ovule
9. Seed formation without fertilisation in flowering plants involves the process of (2016-I)
CHAPTER TEST
1. Vegetative cell of pollen grain differs from generative cells in terms of
A. size
B. extent of food reserves
C. shape of nucleus
(1) A only
(2) B only
(3) C only
(4) A, B and C
(1) somatic hybridisation
(2) apomixis
(3) sporulation
(4) budding
10. Coconut water from a tender coconut is (2015-R)
(1) innermost layers of the seed coat
(2) degenerated nucellus
(3) immature embryo
(4) free nuclear endosperm
11. Geitonogamy involves (2014)
(1) fertilisation of a flower by the pollen from another flower of the same plant
(2) fertilisation of a flower by the pollen from the same flower
(3) fertilisation of a flower by the pollen from a flower of another plant in the same population
(4) fertilisation of a flower by the pollen from a flower of another plant belonging to a distant population
12. Which one of the following statements is correct? (2013)
(1) Endothecium produces the microspores
(2) Tapetum nourishes the developing pollen
(3) Hard outer layer of pollen is called intine
(4) Sporogenous tissue is haploid
2. Pollen tablets are used for/as
(1) fossilisation
(2) germplasm collection
(3) food supplement
(4) food for insect
3. How many mitotic divisions are required to produce mature male gametophyte from microspore?
(1) 1 (2) 2
(3) 3 (4) 4
4. Given below are two statements. One is labelled Assertion (A) and the other is labelled Reason (R).
Assertion (A) : During embryo sac formation, initial mitotic divisions are strictly free nuclear.
Reason (R) : During embryo sac development, nuclear divisions are not followed immediately by cell wall formation.
In light of the above statements, choose the correct answer from the options given below.
(1) Both (A) and (R) are true and (R) is the correct explanation of (A).
(2) Both (A) and (R) are true but (R) is not the correct explanation of (A).
(3) (A) is true but (R) is false.
(4) Both (A) and (R) are false.
5. Multicarpellary syncarpous gynoecium is present in
(1) Nelumbo (2) Papaver
(3) Michelia (4) Rosa
6. Given below are two statements.
Statement I : The process of formation of megaspores from the megaspore mother cell is called megasporogenesis.
Statement II : The process of development of the embryo sac from the functional megaspore, where the egg cell is also formed, is termed as gametogenesis.
In light of the above statements, choose the correct answer from the options given below.
(1) Both statements I and II are correct.
(2) Both statement I and statement II are incorrect.
(3) Statement I is correct but statement II is incorrect.
(4) Statement I is incorrect but statement II is correct.
7. In which stage of embryo sac development, there is movement of nuclei towards opposite poles?
(1) 2 nucleated stage (2) 4 nucleated stage
(3) 6 nucleated stage (4) 7 celled stage
8. Given below are two statements.
Statement I : In a mature pollen grain, two male gametes are formed.
Statement II : An embryo sac has only one female gamete.
In light of the above statements, choose the correct answer from theoptions given below.
(1) Both statement I and statement II are correct.
(2) Both statement I and statement II are incorrect.
(3) Statement I is correct but statement II is incorrect.
(4) Statement I is incorrect but statement II is correct.
9. Embryo sac is best described as (1) progenitor of next generation
(2) mitotic product from zygote
(3) female gametophyte
(4) megasporangium
10. In angiosperms, the functional megaspore in the linear tetrad is generally____ from micropylar end.
(1) first
(2) second
(3) third
(4) fourth
11. In a ovary with 100 ovules ready for fertilisation, how many megaspores fail to form embryo sacs?
(1) 200 (2) 100
(3) 300 (4) 75
12. The type of pollination that brings genetically different types of pollen grains to the stigma of a plant is
(1) xenogamy (2) geitonogamy
(3) chasmogamy (4) autogamy
13. Foul smelled flowers are pollinated by
(1) bees and bats
(2) birds and snakes
(3) bats and snails
(4) flies and beetles
14. Given below are two statements. One is labelled Assertion (A) and the other is labelled Reason (R).
Assertion (A) : Wind is the pollinating agent in corn.
Reason (R) : Corn plant has hidden stamens.
In light of the above statements, choose the correct answer from the options given below.
(1) Both (A) and (R) are true and (R) is the correct explanation of (A).
(2) Both (A) and (R) are true but (R) is not the correct explanation of (A).
(3) (A) is true but (R) is false.
(4) Both (A) and (R) are false.
15. Which one is not an outbreeding device?
(1) Self incompatibility
(2) Dioecy
(3) Close positioning of anther and stigma in a bisexual flower
(4) Occurrence of stigma receptivity and pollen release of a bisexual flower at different times.
16. Flowers are not colourful and do not emit smell, when they are
(1) wind pollinated
(2) insect pollinated
(3) bird pollinated
(4) animal pollinated
17. Total cells involved in double fertilisation of an angiosperm are
(1) two male gametes, one synergid and one egg cell
(2) vegetative cell, one male gamete, egg cell and central cell
(3) two male gametes, egg cell and an antipodal cell
(4) two male gametes, egg cell and central cell
18. Cob is the name given to the inflorescence of (1) Sorghum (2) corn
(3) paddy (4) wheat
19. Given below are two statements.
Statement I : Geitonogamy is genetically similar to autogamy.
Statement II : Geitonogamy occurs between flowers of different plants of the same species.
In the light of given statements, choose the correct answer from the options given below.
(1) Both statement I and statement II are correct.
(2) Both statement I and statement II are incorrect.
(3) Statement I is correct but statement II is incorrect.
(4) Statement I is incorrect but statement II is correct.
20. Flowers of which of the following plant provide safer places for laying eggs by a moth?
(1) Mustard (2) Chillies
(3) China rose (4) Yucca
21. Given below are two statements. One is labelled Assertion (A) and the other is labelled Reason (R).
Assertion (A) : Synergids play an important role in directing pollen tube growth.
Reason (R) : Synergids secrete some chemotropically active substance.
In light of the above statements, choose the correct answer from the options given below.
(1) Both (A) and (R) are true and (R) is the correct explanation of (A).
(2) Both (A) and (R) are true but (R) is not the correct explanation of (A).
(3) (A) is true but (R) is false.
(4) Both (A) and (R) are false.
22. In angiosperms, female flower is called as (1) staminate flower (2) pistillate flower
(3) oogonium (4) bisexual flower
23. A diploid (2n) female plant is crossed with a tetraploid (4n) male plant. What would be the ploidy of embryo and endosperm respectively in the resulting seeds?
(1) Diploid and triploid
(2) Diploid and pentaploid
(3) Triploid and tetraploid
(4) Triploid and hexaploid
24. How many meiotic divisions are required for the formation of 80 zygotes in an angiospermic plant?
(1) 40 (2) 100
(3) 80 (4) 160
25. Zygote is always (1) haploid
(2) diploid
(3) triploid
(4) tetraploid
26. Identify the most common abiotic pollinator.
(1) Water
(2) Temperature
(3) Soil
(4) Wind
27. In which of the following pair of plants, endosperm not only nourishes the embryo but also the seedling to form plantlet during seed germination.
(1) Bean and groundnut
(2) Coconut and groundnut
(3) Coconut and castor
(4) Castor and pea
28. Given below are two statements. One is labelled Assertion (A) and the other is labelled Reason (R).
Assertion (A) : Endosperm in angiosperms is triploid.
Reason (R) : It is formed due to the fusion of three triploid nuclei.
In light of the above statements, choose the correct answer from the options given below.
(1) Both (A) and (R) are true and (R) is the correct explanation of (A).
(2) Both (A) and (R) are true but (R) is not the correct explanation of (A).
(3) (A) is true but (R) is false.
(4) Both (A) and (R) are false.
29. Given below are two statements. One is labelled Assertion (A) and the other is labelled Reason (R).
Assertion (A) : Endosperm formation precedes division in zygote and subsequent development of embryo.
Reason (R) : Endosperm ensures assured nutrition to developing embryo.
In light of the above statements, choose the correct answer from the options given below.
(1) Both (A) and (R) are true and (R) is the correct explanation of (A).
(2) Both (A) and (R) are true but (R) is not the correct explanation of (A).
(3) (A) is true but (R) is false.
(4) Both (A) and (R) are false.
30. A feature of sexual reproduction found only in angiosperms is
(1) a chemical attractant guides the sperm towards the egg
(2) non-motile gametes
(3) one male gamete fuses with egg cell and other fuses with polar nuclei
(4) male gametes are carried by pollen tube.
31. Rearrange the following events of sexual reproduction in the sequence in which they occur in majority of angiospermic plants.
(a) Fertilization
(b) Pollination
(c) Embryogenesis
(d) Gametogenesis
(1) d, b, a, c
(2) b, a, c, d
(3) d, b, c, a
(4) d, a, b, c
32. Each cell of sporogenous tissue in anther is
(1) microspore
(2) pollen
(3) potential pollen mother cell
(4) megaspore mother cell
33. Which oldest seed is excavated from Arctic Tundra?
(1) Lupin arcticus
(2) Phoenix dactylifera
(3) Solanum nigrum
(4) Raphanus sativus
34. Identify the set of fleshy fruits.
(1) Groundnut, cashewnut and mustard
(2) Mango, guava and orange
(3) Wheat, groundnut and rice
(4) Guava, groundnut and wheat
35. Apomixis can lead to formation of a haploid embryo. The cell involved in such case is
(1) nucellar cell without fertilisation
(2) an egg cell without fertilisation
(3) an egg cell by fertilisation
(4) a megaspore mother cell without fertilisation
36. Match Column-I with Column-II.
Column-I Column-II
(A) A whorl of stamens (I) Corolla
(B) A whorl of sepals (II) Calyx
(C) A whorl of carpels (III) Androecium
(D) A whorl of petals (IV) Gynoecium
Select the correct option.
(A) (B) (C) (D)
(1) III II IV I
(2) II III IV I
(3) III IV I II
(4) III I II IV
37. How many male gametes and female gametes are produced by each male and female gametophytes respectively in flowering plants?
(1) One and one
(2) Two and two
(3) One and two
(4) Two and one
38. Match Column-I with Column-II.
Column-I Column-II
(A) Endothecium (I) Cotyledon in cereal grain
(B) Hilum (II) Anther wall layer
(C) Perisperm (III) Persistent nucellus
(D) Scutellum (IV) Region of attachment of funicle with ovular body
Select the correct option.
(A) (B) (C) (D)
(1) II IV III I
(2) I III IV II
(3) III II I IV
(4) IV I II III
39. Match Column-I with Column-II.
Column-I Column-II
(A) Selfincompatibility (I) Grass embryo
(B) Monoecious (II) Perispermic
(C) Epiblast (III) Genetic mechanism
(D) Black pepper (IV) Castor
Select the correct option.
(A) (B) (C) (D)
(1) IV III II I
(2) III IV I II
(3) IV I II III
(4) III I II IV
40. Match Column-I with Column-II.
Column-I Column-II
(A) Vegetative cell (I) Sporopollenin
(B) Generative cell (II) Spindle shaped cell
(C) Exine (III) Large sized and has abundant food reserve
(D) Intine (IV) Cellulose and pectin
Select the correct option.
(A) (B) (C) (D)
(1) I II III IV
(2) IV II III I
(3) III II I IV
(4) II I IV III
41. Choose the correct set of structures with respect to essential units of sexual reproduction of a flower.
A. Calyx
B. Corolla
C. Androecium
D. Gynoecium
(1) A and B only
(2) C and D only
(3) A and C only
(4) B and D only
42. Match Column-I with Column-II.
Column-I (Parts of embryo) Column-II (Features)
(A) Cotyledon (I) Portion below the cotyledon
(B) Epicotyl (II) Portion above the cotyledon
(C) Plumule (III) Tip of epicotyl
(D) Hypocotyl (IV) Embryonic leaf
Select the correct option.
(A) (B) (C) (D)
(1) I II III IV
(2) I III II IV
(3) IV II III I
(4) I II IV III
43. Which of the following statements is correct?
(a) Each ovule/megasporangium has one or two protective envelopes called integuments that encircle the nucellus except at the micropyle.
(b) The chalaza represents the basal part of the ovule.
(c) The central mass of cells called the nucellus has abundant reserve food materials.
(d) In general, a single cell of nucellus in the micropylar region differentiates into a megaspore mother cell (MMC).
(e) The megaspore mother cell divides by meiosis to form four megaspores.
(f) All the four megaspores further undergo mitosis to form the female gametophyte.
(1) a, b, c, d and f only
(2) b, c, d, e and f only
(3) a, b, c, d and e only
(4) a, c, d, e and f only
44. Read the following statements
(A) All the changes from pollen deposition on the stigma until the pollen tube enter the ovule are collectively called pollen pistil interactions.
(B) Chemical dialogue between male gametes and antipodals is a prerequisite for postpollination events.
(C) Pollen tube enters into the ovule from the micropylar end.
(D) Pollen tube directly enters the egg cell to release male gametes.
Pick the correct statement.
(1) A and B only (2) B and C only
(3) A and C only (4) B and D only
45. Read the following statements and pick the correct pair of statements.
(A) True fruits are always associated with false fruits.
(B) False fruits do not possess any seeds.
(C) Thalamus contributes to true fruit formation in apple, cashew and strawberry.
(D) True fruits can have fleshy pericarp as seen in orange and guava, or can be dry as seen in groundnut and mustard.
(1) A and B only (2) B and C only
(3) A and C only (4) B and D only
ANSWER KEY
NEET Drill
Further Exploration
Matching Type
and Reason
Brain Teasers
Chapter Test
HUMAN REPRODUCTION CHAPTER 2
Chapter Outline
2.1 The Male Reproductive System
2.2 The Female Reproductive System
2.3 Gametogenesis
2.4 Menstrual Cycle
2.5 Fertilisation and Implantation
2.6 Pregnancy and Embryonic Development
2.7 Parturition and Lactation
Humans are sexually reproducing and viviparous. The reproductive events in humans include:
■ Gametogenesis: The formation of gametes
■ Insemination: The transfer of sperm into the female genital tract
■ Fertilisation: The fusion of male and female gametes , leading to the formation of the zygote
■ Implantation: The attachment of the blastocyst to the uterine wall (fertilisation is followed by the formation and development of the blastocyst and its implantation)
■ Gestation: The embryonic development
■ Parturition: The delivery of the baby
These reproductive events occur after puberty (sexual maturity).
There are remarkable differences between the reproductive events in the male and in the female. For example, sperm formation continues even in old men, but the formation of the ovum ceases in women around the age of fifty years.
2.1 THE MALE REPRODUCTIVE SYSTEM
The male reproductive system is located in the pelvis region. It includes a pair of testes along with accessory ducts, glands and the external genitalia (Fig. 2.1).
2.1.1 Testes
The testes are paired, oval, pinkish , male primary sex organs suspended outside the abdominal cavity within a pouch called the scrotum .
2.1 Lateral view of male reproductive system
The scrotum helps maintain the low temperature of the testes (2-2.5oC lower than the normal internal body temperature) necessary for spermatogenesis. Each scrotal sac encloses one testis.
The cavity of the scrotal sac is connected to the abdominal cavity through the inguinal canal The testes descend into the scrotum during the seventh month of foetal development. The failure of the testes to descend into the scrotum is called cryptorchidism. It can result in sterility.
Urinary bladder
Seminal vesicle Rectum
Scrotum
Pubic bone
Prostate Gland
Vas deferens
Penis
Urethra
Fig.
In adults, each testis is oval with a length of about 4 to 5 cm and a width of about 2 to 3 cm. It is covered by a dense fibrous capsule called tunica albuginea . Tunica albuginea extends inward to form septa that divide the testis into about 250 testicular lobules. Each lobule contains one to three highly coiled seminiferous tubules in which sperm are produced (Fig.2.2).
Spermatic cord
Vas deferens
Vasa efferentia
Rete testis
Epididymis
Tunica albuginea
Seminiferous tubule
Fig. 2.2 Longitudinal section of testis
Each seminiferous tubule is internally lined by two types of cells: male germ cells (spermatogonia) and Sertoli cells (sustentacular cells).
The spermatogonia produce the primary spermatocytes, which undergo meiotic division, finally leading to sperm production. Sertoli cells provide nutrition to the spermatozoa. They also produce a hormone called inhibin, which inhibits the secretion of FSH.
The interstitial space outside the seminiferous tubules contains interstitial cells or Leydig cells (Fig. 2.3). Leydig cells produce androgens, the most important of which is testosterone. Testosterone controls the development of secondary sexual characters and spermatogenesis. Other immunologically competent
cells (e.g., macrophages and lymphocytes) are also present in the interstitial spaces.
Interstitial cells
Spermatogonia
Spermatozoa
Sertoli cells
Fig. 2.3
The male sex accessory ducts include rete testis, vasa efferentia, epididymis and vas deferens. These ducts store and transport the sperm from the testis to the outside through the urethra. The seminiferous tubules of the testis open into the vasa efferentia through a network of tubules in the testis called rete testis.
2.1.2 Epididymis
The vasa efferentia leave the testis and open into a narrow, tightly coiled tube called epididymis located along the posterior surface of each testis. The epididymis serves for the storage and maturation of sperm (Fig.2.2).
2.1.3
Vasa Deferentia
The vas deferens or ductus deferens is a long, narrow, muscular tube. It starts from the tail of the epididymis, ascends through the inguinal canal into the abdomen and loops over the urinary bladder. The terminal part of the vas deferens and the duct of the seminal vesicle unite to form a short muscular ejaculatory duct. (Fig. 2.4). The two ejaculatory ducts converge in the centre of the prostate and open into the urethra.
Structure of seminiferous tubule
Vas deferens
Prostate
Bulbourethral gland
Urethra
Urethral opening
Fig. 2.4 Male reproductive system (Front view)
2.1.4 Urethra
Bladder
Seminal vesicle
Penis
Epididymis
Testicle
Foreskin
Structure
In males, the urethra is the shared terminal duct of the reproductive and urinary systems. The urethra originates from the neck of the urinary bladder and extends through the penis to its external opening, called the urethral meatus. The urethra provides an exit for urine and semen during ejaculation in males.
2.1.5 Penis
The penis and the scrotum constitute the male external genitalia (Fig.2.5(a)). The penis serves as a urinal duct and also copulatory organ that transfers spermatozoa to the vagina of a female.
The human penis is made up of three columns of spongy tissue – two corpora cavernosa and one corpus spongiosum (Fig. 2.5(b)). Urethra is enclosed by corpus spongiosum
The glans penis is the enlarged, bulbous structure at the tip of the penis. Glans penis is covered by a loose fold of skin (foreskin) called prepuce. The urethra passes through the corpus spongiosum and opens out at the tip of the glans penis by external urethral meatus.
Ventral (b) Transverse section
Fig. 2.5 Penis
The path of passage of spermatozoa:
Seminiferous tubules → Rete testis → Vasa efferentia → Epididymis → Vas deferens → Ejaculatory duct → Urethra → Vagina of the female.
2.1.6
Male Accessory G lands
The male accessory glands (Fig.2.4) include paired seminal vesicles, a prostate gland and paired bulbourethral glands. Secretions of these glands constitute the seminal plasma, which is rich in fructose, calcium and certain enzymes. Fructose is used by sperm for ATP production. Seminal fluid provides a medium for the transport of sperm, nourishes sperm, and neutralises the acidity of the male urethra and the vagina. Semen is a mixture of sperm and seminal fluid.
Corona
Root
Shaft
Neck
Glans penis
Fore skin
External urethral meatus (a)
Skin
Urethra
Corpus Spongiosum
Corpus Cavernosum
Deep Dorsal Vein
Superficial Vein
Dorsal
Seminal Vesicles
A pair of seminal vesicles is located behind the base of the urinary bladder. The duct of each seminal vesicle opens into an ejaculatory duct. The secretions of seminal vesicles contributes to the bulk of the volume of semen.
Prostate Gland
The single prostate gland is located beneath the urinary bladder around the urethra. The prostate gland secretes a fluid that contributes to sperm motility.
Bulbourethral Glands
Bulbourethral glands (Cowper’s glands) are located beneath the prostate gland at the base of the penis. Their secretions lubricate the penis.
Checkpoint
Q. How can cryptorchidism contribute to sterility?
Answer: If testes fail to descend into the scrotum, higher temperatures in the pelvic cavity destroy germ cells.
TEST YOURSELF
1. In the human male reproductive system, ejaculatory duct connects the (1) ureter to the urethra
(2) ureter to the urinary bladder
(3) epididymis to the vas deferens
(4) vas deferens to the urethra
2. Spermatogenesis occurs in the (1) seminal vesicle
(2) epididymis
(3) seminiferous tubules
(4) vas deferens
3. The interstitial spaces in the testes do not contain
(1) Leydig cells
(2) immunocompetent cells
(3) Sertoli cells
(4) blood vessels
4. The secretions of which of the following male accessory glands help in the lubrication of the penis?
(1) Prostate gland
(2) Bulbourethral glands
(3) Skene’s glands
(4) Bartholin’s glands
5. Select the correct set of male accessory glands.
(1) Prostate gland, seminal vesicles and bulbourethral glands
(2) Seminal vesicles, Skene’s glands and Cowper’s glands
(3) Bartholin’s glands, pineal gland and bulbourethral glands
(4) Prostate gland, Bartholin’s gland and bulbourethral glands
6. The number of testicular lobules in each testis of human being is (1) 1 to 3 (2) 25 (3) 250 (4) 2500
7. The seminal plasma is rich in all of the following, except (1) glucose (2) calcium (3) fructose (4) enzymes
Answer Key
(1) 4 (2) 3 (3) 3 (4) 2
(5) 1 (6) 3 (7) 1
2.2 THE FEMALE REPRODUCTIVE SYSTEM
The female reproductive system consists of a pair of ovaries along with a pair of oviducts, uterus, cervix, vagina and external genitalia located in the pelvic region (Fig. 2.6) . These parts of the female reproductive system, along with a pair of mammary glands, are integrated
structurally and functionally to support the processes of ovulation, fertilisation, pregnancy, parturition and child care.
2.2.1 Ovaries
Ovaries are the primary female sex organs that produce the female gametes (ova) and several steroid hormones (ovarian hormones). There are a pair of ovaries, one on each side of the lower abdomen . Each ovary is about 2 to 4 cm in length. The ovaries are anchored to the uterus by the ovarian ligament and attached to the pelvic wall by the suspensory ligament.
Each ovary consists of the following regions, from outside to inside:
■ Germinal epithelium: It is made of simple cuboidal epithelium.
■ Tunica albuginea: It is made of dense connective tissue.
■ Stroma: It is divided into a peripheral cortex and an inner medulla.
• Cortex: It appears more dense and granular due to the presence of numerous ovarian follicles in various stages of development.
• Medulla: It contains loose connective tissue with abundant blood vessels, lymphatic vessels and nerve fibres.
2.2.2 Oviducts (Fallopian tubes)
The oviducts (fallopian tubes), uterus and vagina constitute the female accessory ducts. Each fallopian tube is about 10-12 cm long and extends from the periphery of each ovary to the uterus.
The fallopian tubes serve for the transport of the oocytes released from the ovaries. They are internally lined by ciliated simple columnar epithelium. Ciliated cells and peristaltic contractions help move an ovum (secondary oocyte) or zygote toward the uterus. The fallopian tubes are the normal sites of fertilisation.
Each fallopian tube consists of three parts (Fig. 2.6):
■ Infundibulum: It is the funnel-shaped part closer to the ovary. The edges of the infundibulum possess finger-like projections called fimbriae, which help in the collection of the ovum after ovulation.
■ Ampulla: It is the middle, curved, wider part of the oviduct. It is the site of fertilisation.
■ Isthmus: It is the last narrow part of the oviduct that joins the uterus.
2.2.3 Uterus (Womb)
The uterus is a single large, muscular, highly vascular and inverted pear-shaped structure present in the pelvis between the bladder and the rectum (Fig. 2.6). The uterus is connected to the pelvic wall by a mesentery
The uterus is subdivided into three regions (Fig. 2.7):
■ Fundus: The dome-shaped superior portion
■ Body: Large central portion
■ Cervix: Inferior narrow portion that opens into vagina
The cavity of the cervix is called the cervical canal. The cervical canal and the vagina form the birth canal.
Ovary
Fig. 2.6 Section through female pelvis
The wall of the uterus has three layers:
■ Perimetrium: It is the external thin membranous part.
■ Myometrium: It is the middle thick layer of smooth muscle. It exhibits strong contractions during parturition.
■ Endometrium: It is the inner glandular lining. It undergoes cyclic changes during the menstrual cycle.
Uterine fundus
Uterine cavity
Endometrium
Myometrium
The ves tibule is a centrally located depression, bounded by two pairs of fleshy folds of tissue called labia minora and labia majora. It has two apertures – an anterior external urethral orifice and a posterior vaginal orifice.
■ Mons p ubis is a cushion of fatty tissue covered by skin and pubic hair.
■ Labia majora are two longitudinal fleshy folds of skin that extend from the mons pubis and surround the vaginal opening.
Perimetrium Isthmus
Ovary Fimbriae Cervix Cervical canal
2.7 Parts of the female reproductive system
The uterus functions in menstruation, implantation of a fertilised egg, development of a foetus during pregnancy, and parturition (childbirth).
2.2.4 Vagina
The vagina is a large, median, fibromuscular tube that extends from the cervix to the vestibule. It is lined by non-keratinised stratified squamous epithelium. It is highly vascular and opens into the vestibule by the vaginal orifice.
The vagina is a passageway for sperm and the menstrual flow, the receptacle of the penis during sexual intercourse, and a part of the birth canal.
2.2.5 The Female External Genitalia ( Vulva)
The female external genitalia (vulva) include the mons pubis, labia majora, labia minora, hymen and clitoris (Fig. 2.8).
■ Labia minora are two smaller folds of skin medial (inner) to the labia majora.
■ The clitoris is a sensitive, erectile structure that lies at the upper (anterior) junction of the two labia minora above the urethral opening. It is homologous to the penis of the male (Table 2.1)
■ The hymen is a mucous membrane that partially covers the vaginal orifice.
The hymen is often torn during the first coitus (intercourse). However, it can also be broken by a sudden fall or jolt, insertion of a vaginal tampon, active participation in some sports like horseback riding, cycling etc. In some women, the hymen persists even after coitus. The presence or absence of hymen is not a reliable indicator of virginity or sexual experience.
Fallopian tube
Fig.
Mons pubis
Urethral opening
Clitoris
Labia majora
Labia minora
Perineum
Vaginal opening
Anus
Fig. 2.8 External genitalia
The accessory reproductive glands of the female include the paraurethral (Skene’s), greater vestibular (Bartholin’s), and lesser vestibular glands.
Table 2.1 Homologous parts of male and female reproductive systems
Male Female
Testes Ovaries
Scrotum Labia majora
Penis Clitoris
Prostate Skene’s gland
Cowper’s glands Bartholin’s glands
2.2.6 Mammary Glands
Functional mammary glands are characteristic of all female mammals. The mammary glands can be considered part of both the integumentary system and the female reproductive system. Mammary glands are the modified sweat glands. The mammary glands in female humans are paired structures (breasts) that contain glandular tissue and variable amounts of fat. The glandular tissue of each breast is divided into 15–20 mammary lobes containing clusters of cells called alveoli. The cells of the alveoli secrete milk, which is stored in the cavities (lumens) of the alveoli. The alveoli open into mammary tubules. The mammary tubules of each lobe join to form a mammary duct. Several mammary ducts join to form a wider mammary ampulla which is connected to the lactiferous duct in the ‘nipple’ through which milk is sucked out by the baby (Fig. 2.9).
Oestrogen and progesterone mainly promote the development of mammary glands and alveoli. Milk production is stimulated mainly by prolactin. Milk ejection is stimulated by oxytocin.
Recall the path of milk in the mammary gland with the mnemonic ‘All Mothers Make Abundant Love’. Mammary A lveoli → M ammary tubule → M ammary duct → mammary A mpulla → L actiferous duct. Remember that a tubule is smaller than a duct, and alveoli are the starting point.
TEST YOURSELF
1. Birth canal is formed by the (1) uterus and vagina (2) uterus and cervix
(3) cervical canal and vagina (4) cervical canal and inguinal canal
2. The glandular tissue of each breast is divided into
(1) 5-10 mammary lobes
(2) 30–40 mammary lobes
(3) 20-30 mammary lobes
(4) 15–20 mammary lobes
3. Finger-like projections of the oviduct are called
(1) acini (2) villi
(3) fimbriae (4) rugae
Fig. 2.9 L.S. of mammary gland
4. In the female external genitalia, the cushion of fatty tissue covered by skin and pubic hair is termed
(1) mons pubis (2) labia majora
(3) labia minora (4) clitoris
5. Which of the following is shaped like an inverted pear?
(1) Infundibulum
(2) Uterus
(3) Ovary
(4) Vagina
6. Which of the following undergoes cyclical changes during menstrual cycle?
(1) Myometrium (2) Endometrium
(3) Mesometrium (4) Perimetrium
Answer Key
(1) 3 (2) 4 (3) 3 (4) 1
(5) 2 (6) 2
2.3 GAMETOGENESIS
Gametogenesis is the process of formation of gametes (sperm and ovum) from the primary sex organs (testes and ovaries). Gametogenesis in a male is called spermatogenesis, and that in a female is called oogenesis.
2.3.1 Spermatogenesis
Spermatogenesis is the process by which sperm cells are produced in the testes. It consists of several phases:
Spermatocytogenesis
The spermatogonia (2n) present in the inner lining of seminiferous tubules multiply by mitotic division and develop into spermatocytes. Each spermatocyte is diploid and contains 46 chromosomes (Fig. 2.10).
Spermatidogenesis
Primary spermatocytes periodically undergo meiosis to produce spermatids.
Meiosis I: A primary spermatocyte completes the first meiotic division, leading to the formation of two secondary spermatocytes. Since meiosis I is a reductional division, secondary spermatocytes are haploid, each with 23 chromosomes.
Meiosis II: The two secondary spermatocytes undergo the second meiotic division to produce four equal spermatids. Meiosis II is equational, and hence the spermatids are haploid, each with 23 chromosomes.
Spermiogenesis
Each haploid spermatid is transformed into a haploid spermatozoon (sperm). During spermiogenesis, spermatids undergo further structural changes and differentiation to become mature spermatozoa. At the end of spermiogenesis, sperm heads are embedded in the Sertoli cells.
The events in spermiogenesis are:
■ Formation of acrosome from the Golgi complex at the tip of the sperm
■ Shedding of excess cytoplasm
■ Elongation and condensation of the nucleus
■ Separation of centrioles
■ Development of a tail or flagellum (axial filament)
■ Development of mitochondrial spiral
No cell division occurs during spermiogenesis.
Spermiation
Sperm cells are released from the epithelium of the seminiferous tubules into the lumen of the seminiferous tubules.
DIPLOID (2n)
DIPLOID (2n)
DIPLOID (2n)
HAPLOID (n)
HAPLOID (n)
HAPLOID (n)
HAPLOID (n)
Fig. 2.10 Spermatogenesis
Hormonal Regulation of Spermatogenesis
Spermatogen esis starts at puberty due to a significant increase in the secretion of gonadotropin releasing hormone (GnRH) f from the hypothalamus. The increased levels of GnRH stimulate the anterior pituitary (adenohypophysis) to secrete two gonadotropins - luteinising hormone (LH) and follicle stimulating hormone (FSH).
LH acts on the Leydig cells and stimulates the secretion of testosterone (androgen). Testosterone, in turn, stimulates the process of spermatogenesis (Fig. 2.11) . The excess level of testosterone inhibits the secretion of LH from the anterior pituitary and GnRH from the hypothalamus.
FSH acts on the Sertoli cells and stimulates the secretion of some factors (such as androgen binding proteins and inhibin) that help in the process of spermiogenesis. These factors create a supportive environment for sperm development. Spermiogenesis is triggered directly by testosterone.
■ Androgen binding proteins (ABPs) help in spermiogenesis by concentrating testosterone in the seminiferous tubules.
■ Growth factors support the proliferation and differentiation of spermatocytes.
■ Inhibin mainly acts on the anterior pituitary gland and inhibits the secretion of FSH (once the degree of spermatogenesis required for male reproductive functions has been achieved).
Structure of a Sperm Cell
The spermatozoon is a microscopic cell consisting of a head, neck, middle piece and tail. A plasma membrane envelops the whole body of the spermatozoon (Fig. 2.12).
Head
The head of a spermatozoon contains an elongated haploid nucleus. The anterior portion of the nucleus is covered by a cap-like structure called the acrosome. The acrosome contains numerous enzymes that facilitate fertilisation by aiding the penetration of the sperm into the ovum.
The acrosome contains numerous enzymes called sperm lysins such as proteases, acid phosphatase and hyaluronidase.
Fig. 2.11 Hormonal control of spermatogenesis
Neck
It is a short, narrow structure between the head and the middle piece. Its cytoplasm contains two centrioles.
The proximal centriole plays a role during the first cleavage of the fertilised ovum. The distal centriole gives rise to the axial filament, which extends into the tail.
Middle piece
The middle piece contain numerous mitochondria . Mitochondria produce energy for the movement of the tail that facilitate sperm motility, which is essential for fertilisation. Acrosome Neck
The correct plural form of ‘sperm’ is also ‘sperm’, not ‘sperms’.
Sperm released from the seminiferous tubules are transported by the accessory ducts. Secretions of the epididymis, vas deferens, seminal vesicle and the prostate are essential for the maturation and motility of sperm. The seminal plasma, along with the sperm, constitutes the semen. The functions of male sex accessory ducts and glands are maintained by the androgens, testicular hormones.
2.3.2 Oogenesis
Fig. 2.12 Structure of sperm
The Nebenkern is a sheath of fused mitochondria in the middle piece of the sperm.
Tail
It is the longest part of a sperm, with axial filament throughout its length. The sperm swims with the help of the tail. Recall that this as an example of flagellar movement .
Sperm motility is essential for fertilisation. A human male ejaculates about 200 to 300 million sperm during coitus. At least 60 per cent sperm cells must have normal shape and size, and at least 40 per cent of them must show vigorous motility for normal fertility.
Oogenesis (Fig. 2.15) is the process of the formation and development of mature female gametes, also known as ova. Oogenesis begins during the embryonic development stage. Two million oogonia (egg mother cells) are formed within each foetal ovary. They do not multiply after birth. The oogonia differentiate into primary oocytes. They start meiotic division, progressing into prophase-I, and are temporarily arrested at this stage.
Follicular Development
An ovarian follicle is a structure in the ovarian cortex consisting of an oocyte surrounded by follicle or granulosa cells. A follicle undergoes a series of developmental stages, ultimately forming a mature or Graafian follicle.
Primary Follicle
It is an early stage formed before birth. Each primary follicle contains an oocyte surrounded by a layer of granulosa cells. A large number of primary follicles degenerate during the phase from birth to puberty. At puberty, only 60,000 to 80,000 primary follicles are left in each ovary.
The process of degeneration of follicles is known as follicular atresia.
Secondary Follicle
The follicular cells of a primary follicle become cuboidal and multiply to form several layers of granulosa cells. The granulosa cells are surrounded by a theca made up of stromal cells. These follicles are called secondary follicles.
Tertiary Follicle
The secondary follicle transforms into a tertiary follicle, which is characterised by the presence of an antrum. The antrum is a fluidfilled cavity that develops between granulosa cells (Fig. 2.13) . The theca differentiates into two layers:
■ Theca interna: The inner layer of cuboidal secretory cells.
■ Theca externa: The outer layer of stromal cells and collagen fibres.
The cells of theca interna and granulosa cells secrete the hormone oestrogen.
Graafian Follicle
The primary oocyte within the tertiary follicle grows in size and completes its first meiotic division. It is an unequal division resulting in the formation of a large haploid secondary oocyte and a tiny first polar body. The secondary oocyte retains the bulk of the nutrient-rich cytoplasm of the primary oocyte.
The first polar body typically degenerates soon after its formation. The secondary oocyte begins the second meiotic division, but the division stops at metaphase–II.
Polar bodies are byproducts of unequal cell division during oogenesis. The mature egg or ovum retains most of the cytoplasm, supplying essential nutrients for early developmental stages. The polar bodies discard excess genetic material, ensuring only one viable egg with a haploid set of chromosomes is produced per menstrual cycle.
The mature follicle is called the Graafian follicle (Fig. 2.14) . The secondary oocyte at this stage has a glycoprotein layer called zona pellucida. The zona pellucida is secreted by the oocyte itself. The layer of granulosa cells firmly attached to zona pellucida is called corona radiata.
Ovulation
The Graafian follicle ruptures to release the secondary oocyte (ovum) from the ovary into the pelvic cavity. This process is called ovulation (Fig. 2.15).
Tertiary follicle Secondary follicle
follicle
albicans
luteum
Ovulation
Mature follicle
(Graafian folllicle)
Fig. 2.13 Diagrammatic sectional view of ovary
Fig. 2.14 Structure of a Graafian follicle
Fig. 2.15 Oogenesis
The secondary oocyte that is shed from the ovary is surrounded by a plasma membrane called oolemma. Tiny vesicles, called cortical granules, lie just under the egg’s plasma membrane (Fig. 2.14). Between the oolemma and the zona pellucida, is a distinct space called perivitelline space, in which the first polar body is located.
Corpus Luteum
After ovulation, the ruptured Graafian follicle transforms into the corpus luteum . It is a temporary endocrine structure that primarily secretes progesterone.
If the ovum is not fertilised, the corpus luteum persists for about 14 days and eventually regresses, forming corpus albicans (white body)
If the ovum is fertilised, leading to pregnancy, the corpus luteum remains for three to four months. The progesterone it produces is crucial for sustaining the early
stages of pregnancy. After this period, the placenta takes over progesterone secretion.
2.3.3 Spermatogenesis Vs Oogenesis
There are several fundamental differences between spermatogenesis and oogenesis in humans, as outlined in the Table 2.2 and Fig. 2.16
Table 2.2 Differences between spermatogenesis and oogenesis.
Spermatogenesis Oogenesis
Location Seminiferous tubules of the testes Ovarian follicles of the ovary
Begins At puberty Before birth
Frequency Daily One egg is released per cycle.
Duration About 72 days Years
No. of cell divisions during meiosis 4 3
Nature of meiosis Continuous Discontinuous
Cell cycle Not arrested Arrested at prophase I and metaphase II
Type of cell divisions during meiosis Equal Unequal
No. of gametes formed from one primary gamete mother cell 4 1
Number of polar bodies 0 2
Motility of gamete Small and motile Large and nonmotile
Total number of gametes produced 200 to 300 million per ejaculate
About 400 in lifetime
Spermatogonia
Fig. 2.16 Spermatogenesis vs oogenesis
Checkpoint
Q. If an egg is removed surgically from the ovary of a 10-year-old girl, at what stage of cell cycle will that be?
Answer: Prophase I of Meiosis I
TEST YOURSELF
1. The rel ease of mature sperm from Sertoli cells into the lumen of the seminiferous tubule is termed (1) spermiogenesis
(2) insemination
(3) spermiation
(4) ejaculation
2. During oogenesis in humans, the secondary oocyte completes meiosis II (1) at the time of ovulation
(2) at the time of fertilisation after the entry of the sperm into the oocyte (3) at the time of coitus
(4) at the time of fertilisation before the entry of the sperm into the oocyte
3. In oogenesis, which cells are produced after the first meiotic division?
(1) Primary oocyte and first polar body
(2) Primary oocyte and second polar body
(3) Secondary oocyte and first polar body
(4) Secondary oocyte and second polar body
4. Spermatogenesis starts at (1) embryonic development
(2) birth (3) puberty
(4) middle age
5. Maturation of spermatids into sperm is termed (1) spermiogenesis (2) spermiation
(3) capacitation
(4) ejaculation
6. During oogenesis, second meiotic division is completed in (1) ovary (2) fallopian tube (3) uterus (4) vagina
7. At the end of spermiogenesis, sperm heads remain embedded in the
(1) Sertoli cells
(2) Leydig cells
(3) Paneth cells
(4) Kupffer cells
8. The membrane that immediately surrounds the secondary oocyte is (1) zona reticularis (2) corona radiata
(3) zona fasciculata (4) zona pellucida
9. The fluid-filled cavity in a tertiary ovarian follicle is termed (1) antrum
(2) theca
(3) lacuna
(4) alveolus
10. The acrosome of the sperm contains (1) enzymes that help in fertilisation (2) hormones that enhance libido
(3) mitochondria that provide ATP (4) centrioles that initiate cleavage
11. In a mammalian sperm, spirally arranged mitochondria around the axial filament are present in the region of (1) head
(2) middle piece
(3) principal piece of tail
(4) end piece of tail Answer Key
(1) 3 (2) 2 (3) 3 (4) 3 (5) 1 (6) 2 (7) 1 (8) 4
(9) 1 (10) 1 (11) 2
2.4 MENSTRUAL CYCLE
The reproduc tive cy cle in fe male primates, such as monkeys, apes, human beings, etc., is called the menstrual cycle. Menarche, the first occurrence of menstruation, occurs at puberty. In human beings, menstrual cycles
cease around 50 years of age. The natural cessation of menstrual cycles is referred to as menopause.
Cyclic menstruation is an indicator of the normal reproductive phase, extending between the menarche and the menopause. The typical length of the menstrual cycle in humans is 28 or 29 days. One ovum (more precisely, a secondary oocyte) is released during the middle of each menstrual cycle.
The female reproductive cycle includes the ovarian and uterine cycles that occur simultaneously. The ovarian cycle involves events in the ovaries leading to the maturation and release of an oocyte. The uterine (menstrual) cycle comprises simultaneous changes in the endometrium of the uterus, preparing it for the potential implantation of a fertilised ovum. These changes in the ovary and the uterus are induced by changes in the levels of pituitary and ovarian hormones.
2.4.1 Phases of Menstrual Cycle
The cycle of events from one menstruation to the next is called the menstrual cycle. Each cycle includes menstrual phase, follicular phase, ovulation and luteal phase. The following description applies to a typical 28day menstrual cycle (Fig. 2.17).
Fig. 2.17 Menstrual cycle
Menstrual Phase
Menstruation or menses is considered the first phase of menstrual cycle. This lasts about 3 to 5 days, starting from day 1 of the cycle.
Hormone levels
■ During the menstrual phase, progesterone and oestrogen levels decline since the corpus luteum degenerates by the end of the previous cycle in the absence of fertilisation.
■ FSH and LH levels are low.
Events in the ovary
■ Most ovarian follicles are in the early stages of development or quiescent (inactive)
Events in the uterus
■ This phase primarily focuses on the shedding of the uterine lining.
■ The menstrual flow results from the breakdown of the endometrial lining of the uterus and its blood vessels due to declining levels of progesterone and oestrogen. The menstrual discharge passes to the exterior through the cervix and the vagina.
■ It is important to note that menstruation occurs only if the ovum released in the previous cycle is not fertilised.
■ Absence of menstruation may be indicative of pregnancy. However, it may also be caused by some other causes like stress, poor health etc.
Follicular Phase (Proliferative Phase)
This phase lasts from days 6 to 13. It is more variable in length than the other phases.
Hormone levels
■ FSH and LH levels increase gradually towards the end of the follicular phase.
■ FSH and LH stimulate the ovarian follicles to secrete oestrogens. Oestrogen levels peak around the 12th day.
■ Progesterone levels remain low since there is no corpus luteum to secrete it.
Events in the ovary
■ FSH initiates follicular growth, while LH stimulates further development of the ovarian follicles. Oestrogens also aid in follicular growth. The name follicular phase refers to the follicular growth and development of the follicles.
■ A primary follicle in either ovary grows to become a fully mature Graafian follicle. This follicle forms a bulge on the surface of the ovary.
Normally, the one dominant secondary follicle becomes the mature (Graafian) follicle. Other follicles undergo atresia under the influence of inhibin and oestrogen secreted by the dominant follicle. Fraternal (dizygotic) twins result when two codominant secondary follicles ovulate, and subsequently the two ova get fertilised.
Events in the uterus
■ The endometrium of the uterus regenerates through proliferation (hence the name proliferative phase).
■ Oestrogens stimulate the repair of the endometrium.
■ The thickness of the endometrium roughly doubles.
Ovulatory Phase
Ovul ation occurs during the middle of the cycle (around 14th day).
Hormone Levels
■ Both LH and FSH attain a peak level in the middle of the cycle (day 14).
■ High levels of oestrogens exert a positive feedback effect, leading to increased secretion of GnRH and LH during the mid-cycle (low levels of oestrogens during other phases of the menstrual cycle exert a negative feedback effect, leading to decreased secretion of GnRH, FSH and LH).
■ Rapid secretion of LH leading to its maximum level during the mid-cycle is called LH surge (Fig. 2.18).
Events in the ovary
■ LH surge induces the rupture of the Graafian follicle and, thereby, the release of the ovum at the secondary oocyte stage (ovulation) into the pelvic cavity. The secondary oocyte remains surrounded by its zona pellucida and corona radiata.
Ovulation typically occurs around 14 days before the start of the next menstrual period. So, subtract 14 days from the total duration of the menstrual cycle to estimate the potential day of ovulation. For example, if the menstrual cycle is 28 days long, ovulation is expected on 28–14 = 14 th day. If the menstrual cycle is 32 days long, ovulation is expected on 32–14=18th day.
Luteal Phase (Secretory Phase)
This phase extends between ovulation and the onset of the next menses. It lasts from day 15 to day 28.
Hormone levels
■ The corpus luteum secretes large amounts of progesterone, which is essential for the maintenance of the uterine endometrium and its secretory function. It also secretes oestrogens.
■ The progesterone level peaks around day 21. The second (smaller) peak of oestrogen appears a few days later.
■ Progesterone inhibits the release of GnRH from the hypothalamus, leading to a decline in FSH and LH levels.
Events in the ovary
■ The remnants of the Graafian follicle transform into the corpus luteum under the influence of LH. The luteal phase is named after and characterised by the presence of the corpus luteum.
■ The decline in FSH and LH prevents further development of follicles and ovulation.
Events in the uterus
■ Progesterone promotes the growth and the vascularisation of endometrium.
■ Oestrogens secreted by the corpus luteum thicken the endometrium further. Such an endometrium is essential for the implantation of the fertilised ovum, more precisely, the blastocyst, and other events related to pregnancy.
■ Progesterone stimulates the endometrium to synthesise and secrete glycogen (hence the name secretory phase). The glycogen provides an energy source for the early embryo.
■ Progesterone inhibits uterine movements and supports pregnancy.
High progesterone levels during the luteal phase suppress FSH secretion. This inhibits the development of new follicles. The focus shifts from the development of new follicles to the maintenance of the uterine lining and preparation for a potential pregnancy.
2.4.2 Impact of Pregnancy on Menstrual Cycle
■ During pregnancy, all events of the menstrual cycle stop, and there is no menstruation.
■ In the absence of fertilisation, the corpus luteum degenerates. This causes disintegration of the endometrium, leading to menstruation and marking a new cycle.
The oe strous cycle is the female reproductive cycle in nonprimate mammals. In the absence of pregnancy, the lining of the uterus is reabsorbed instead of being shed. The oestrous cycles occur exclusively during the breeding season.
Oestrogen is responsible for the initial growth and thickening of the endometrium during the proliferative phase, while progesterone helps maintain the endometrium and prepares it for potential pregnancy during the luteal phase.
Fig. 2.18 Ovarian and uterine events during menstrual cycle
2.4.3 Menstrual Hygiene
Maintenance of hygiene and sanitation during menstruation is very important.
■ Take a bath and clean yourself regularly.
■ Use sanitary napkins or clean homemade pads.
■ Change sanitary napkins or homemade pads after every 4-5 hrs as per the requirement.
■ Dispose of the used sanitary napkins properly wrapping it with a used paper.
■ Do not throw the used napkins in the drainpipe of toilets or in open areas.
■ Wash hands with soap after handling the napkin.
Checkpoint
Q. The blood levels of which hormone among oestrogen, progesterone, FSH, and LH is the lowest around the time of ovulation in a woman?
Answer: Progesterone
TEST YOURSELF
1. Immediately after ovulation, the ruptured Graafian follicle transforms into
(1) corpus callosum
(2) corpus albicans
(3) corpus luteum
(4) corpus spongiosum
2. Corpus luteum produces large amounts of (1) estradiol
(2) testosterone
(3) progesterone
(4) FSH
3. In a typical 28-day menstrual cycle, oestrogen levels are highest around
(1) 5th day
(2) 12th day
(3) 21st day
(4) 28th day
4. The levels of both oestrogen and progesterone are minimum
(1) during late follicular phase
(2) mid luteal phase
(3) at the time of ovulation
(4) at the onset of menstruation
5. The regeneration of endometrium during proliferative phase of menstrual cycle is stimulated by (1) relaxin
(2) testosterone
(3) progesterone
(4) oestrogen
6. L.H surge induces (1) ovulation
(2) menstruation
(3) parturition
(4) fertilisation
7. Ovulation in humans involves the release of (1) oogonium
(2) primary oocyte
(3) secondary oocyte
(4) mature ovum
8. Menstruation occurs due to a decline in the blood levels of
(1) LH
(2) oxytocin
(3) FSH
(4) progesterone
Answer Key
(1) 3 (2) 3 (3) 2 (4) 4 (5) 4 (6) 1 (7) 3 (8) 4
2.5 FERTILISATION AND IMPLANTATION
During coitus, semen is ejaculated through the penis into the vagina (insemination).
Spermatozoa acquire the ability to fertilise the
ovum only after undergoing some changes in the female genital tract. These changes are called capacitation.
Capacita tion is the process by which sperm undergoes physiological changes in the female reproductive tract, enabling them to fertilise an egg. This includes alterations to the sperm’s membrane and increased motility .
2.5.1 Fertilisation
The motile spermatozoa swim rapidly, pass through the cervix, enter the uterus, and finally reach the ampullary region of the fallopian tube. The ovum released by the ovary is also transported to the ampullary region, where fertilisation takes place. Fertilisation can only occur if the ovum and sperm are transported simultaneously to the site of fertilisation. This is the reason why not all copulations lead to fertilisation and pregnancy.
Fig. 2.19 Structure of ovum
The process of fusion of a sperm with an ovum is called fertilisation. During fertilisation, a sperm comes in contact with the zona pellucida layer of the ovum and induces changes in the membrane that block the entry of additional sperm. Thus, only one sperm can fertilise an ovum (monospermy).
Fast block to polyspermy occurs due to the deoplarisation of oocyte’s cell membrane which prevents the fusion of another sperm. Slow block t o polyspermy involves the exocytosis of cortical granules from the egg’s cytoplasm (cortical reaction). These granules contain enzymes that solidify the zona pellucida, making it impermeable to further sperm binding a nd fusion (zona reaction).
Acrosomal enzymes facilitate sperm entry into the cytoplasm of the ovum through the zona pellucida and the plasma membrane, inducing the completion of the meiotic division of the secondary oocyte. The second meiotic division is also unequal and results in the formation of a second polar body and a haploid ovum (ootid). Soon, the haploid nucleus of the sperm (male pronucleus) and that of the ovum (female pronucleus) fuse to form a diploid zygote (Fig. 2.19).
Acrosomal enzymes include hyaluronidase that dissolves hyaluronic acid in the extracellular matrix and acrosin that digests zona pellucida.
Sex of the Baby
The sex of the baby is decided at the time of fertilisation itself. In human beings, sex is determined on the basis of sex chromosome pattern. The sex chromosomes of males are XY, and those of females are XX.
During spermatogenesis among males, two types of gametes are produced; 50% of sperm carry the X-chromosome, and the remaining 50% carry the Y -chromosome besides autosomes.
In case the ovum is fertilised by a sperm carrying X-chromosome, the zygote develops
into a fe male. If the ovum is fertilised by a sperm carrying Y-chromosome, the zygote develops into male offspring (Fig. 2.20). Thus, the sex of the baby depends on the type of the sperm that fertilises the ovum
2.5.2 Cleavage
The mitotic division called cleavage starts as the zygote moves towards the uterus through the isthmus of the oviduct. The cells formed as a result of cleavage are called blastomeres. The cleavages form 2,4,8,16 daughter cells called blastomeres (Fig. 2.21). The term embryo refers to the developmental stage up to the first eight weeks after fertilisation. From the beginning of the ninth week, the developing organism is called a foetus.
During cleavage, the embryo’s volume remains roughly constant as the individual blastomeres progressively decrease in size. The DNA content of the embryo increases due to mitotic divisions without a considerable increase in cytoplasmic mass.
Fig. 2.20 Sex determination
Fig. 2.21 Transport of ovum, fertilisation, cleavage and passage of growing embryo through fallopian tube
2.5.3 Morula
When the number of daughter cells is 8-16, the solid ball of cells is called a morula, as it looks like a mulberry. The zona pellucida still surrounds the tiny embryo.
2.5.4 Formation of Blastocyst (Blastulation)
The morula continues to divide and transforms into a blastocyst as it moves further into the uterus. Outer peripheral cells enlarge and become flattened to form trophoblast or trophectoderm (outer epithelium of the blastocyst), and the inner cells remain as inner cell mass (formative cells). The spaces formed between the trophoblast and inner cell mass are fused to form a cavity called blastocoel (Fig. 2.22).
The inner cell mass gives rise to the embryo. It contains stem cells, which have the potency to give rise to all the tissues and organs.
M onozygotic (identical) twins develop from a single fertilised ovum. They are genetically identical and hence are always of the same sex. The process involves the separation of developing cells into two embryos, which mostly occurs before day 8 of development. Separation that occurs after 8 days is more likely to produce conjoined twins.
Inner cell mass
Trophoblast
Blastocoel
Fig. 2.22 Blastocyst
2.5.5 Implantation
It is the embedding of the blastocyst into the endometrium of the uterus. The cells of the trophoblast stick to the uterine endometrium. The wall of the trophoblast develops chorionic villi that branch and project into the highly vascular uterine endometrium to draw nourishment for the embryo.
The uterine cells divide rapidly and cover the blastocyst. Implantation leads to pregnancy.
After implantation, the endometrium becomes modified and is known as the decidua.
Checkpoint
Q. What unique feature of cell division during cleavage in the developing embryo allows for efficient gas exchange? (hint: surface-to-volume ratio)
Answer: During cleavage, the developing embryo undergoes rapid cell divisions, with each division resulting in progressively smaller daughter cells. This provides a higher surface area-to-volume ratio for a more efficient exchange of gases, ensuring sufficient oxygen supply for the rapidly dividing cells and their growing metabolic demands.
TEST YOURSELF
1. The type of allosome(s) present in gametes of human female is/are
(1) X-chromosome
(2) Y-chromosome
(3) X or Y chromosome
(4) X and Y chromosome
2. The embryonic stage that gets implanted into uterine endometrium is
(1) morula
(2) blastocyst
(3) zygote
(4) gastrula
3. Fertilisation can only occur if (1) sperm is released into the vagina exactly at the time of ovulation
(2) coitus takes place during night time
(3) insemination takes place during menstruation
(4) the ovum and sperm are transported simultaneously to the ampullary region of the fallopian tube
4. The process by which the embryo attaches to the endometrium of the uterus is termed
(1) implantation
(2) gastrulation
(3) parturition
(4) blastulation
5. The number of chromosomes in the human zygote is (1) 46
(2) 23
(3) 45
(4) 22
Answer Key
(1) 1 (2) 2 (3) 4 (4) 1
(5) 1
2.6 PREGNANCY AND EMBRYONIC DEVELOPMENT
After im plantation, the inner cell mass (embryo) differentiates into an outer layer called ectoderm and an inner layer called endoderm. A mesoderm soon appears between the ectoderm and the endoderm. All tissues and organs of the adult are derived from these three primary germ layers (Fig. 2.23).
The i n ner cell mass differentiates into hypoblast and epiblast. Gastrulation is the process in which the cells of epiblast rearrange into ectoderm, mesoderm, and endoderm. The large-scale movements of cells during gastrulation are known as morphogenetic movements.
connection between the developing foetus and the mother’s uterine wall. It plays a crucial role in facilitating nutrient exchange, waste elimination, and hormone production to support foetal development.
Formation of the Placenta
2.6.1 Extraembryonic (Foetal) Membranes
Foetal membranes are membranous coverings and sacs connected to the embryo. These are amnion chorion, allantois and yolk sac ( Fig. 2.24).
■ Amnion: The amnion is a fluid-filled sac that surrounds and protects the developing embryo.
■ Chorion: The chorion is the outermost membrane that contributes to the formation of the placenta.
■ Yolk Sac: It plays a role in the the development of the digestive tract.
■ Allantois: It is involved in the removal of embryonic waste products.
2.6.2 Placenta
The human placenta is a vital organ formed during pregnancy, serving as a temporary
The placenta originates from both embryonic and maternal tissues. It is primarily formed from the chorionic villi, finger-like projections of the trophoblast. They extend into the uterine tissue and maternal blood. Maternal blood vessels and chorionic villi interdigitate with each other and jointly form the placenta. The placenta is a structural and functional unit between the developing embryo (foetus) and the maternal body. The placenta is connected to the embryo through an umbilical cord, which helps in the transport of substances to and from the embryo (Fig. 2.24).
Functions of the Placenta
■ Nutrient and Gas Exchange: The placenta facilitates the supply of oxygen and nutrients to the embryo.
■ Waste Removal : The placenta helps remove carbon dioxide and excretory/ waste materials produced by the embryo.
■ Transport of Substances: The placenta is connected to the embryo through an umbilical cord which helps in the transport of substances to and from the embryo.
■ Hormone Production: The placenta acts as an endocrine tissue and produces hormones crucial for maintaining a healthy pregnancy. These hormones include hCG, hPL, oestrogens, progestogens, etc. In the later phase of pregnancy, a hormone called
Fig. 2.23 Gastrulation
relaxin is also secreted by the ovary. It may be noted that hCG, hPL and rel axin are produced in women only during pregnancy.
■ Immune Support: The placenta contributes to immune protection by preventing the direct transfer of maternal antibodies to the foetus.
Placental Hormones
1. Human Chorionic Gonadotropin (hCG)
This hormone supports the early stages of pregnancy. Like LH, it maintains the corpus luteum, which produces progesterone during the first trimester.
The common pregnancy test, known as the Gravindex test, detects the presence of hCG in a woman’s urine or blood.
2. Human Placental Lactogen (hPL)
It inhibits the uptake of glucose by maternal cells to ensure that glucose is available for foetal growth and development.
3. Progesterone and Oestrogen
These hormones are initially produced by the corpus luteum. The placenta takes over their production during pregnancy. They are essential for maintaining the uterine lining and supporting foetal development. Oestrogens promote uterine growth and the development of the mammary glands.
Hormonal Changes During Pregnancy
During pregnancy, the levels of other hormones like oestrogens, progestogens, cortisol, prolactin, thyroxine, etc., are increased severalfold in the maternal blood. Increased
production of these hormones is essential for supporting foetal growth, metabolic changes in the mother and maintenance of pregnancy
Fig. 2.24 The human foetus within the uterus
2.6.3 Timetable of some events during Pregnancy
Pregnancy is the intrauterine development of the embryo or foetus (also called the gestation period ). The human pregnancy lasts about nine months. The gestation period in some animals is given in Table. 2.3.
Table 2.3 Gestation Periods in Different Mammals
Developmental Changes in the Human Embryo
The avera ge duration of human pregnancy (gestation period) is about 9 months. Human gestation can be divided for convenience into three trimesters of about three months each.
Chorion
Amnion
Embryo
Allantois
Yolk sac
Fetal portion of placenta
Maternal portion of placenta
Chorionic villi
Cavity of uterus
Plug of mucus in cervix
Umbilical cord
Table 2.4 Developmental Milestones
Time
After one month
By the end of the second month
By the end of 3rd month
Developmental Milestone
The embryo’s heart is formed. The first sign of a growing foetus may be noticed by listening to the heart sounds carefully using a stethoscope.
The foetus develops limbs and digits.
Most of the major organ systems are formed (organogenesis). The limbs and external genital organs are well-developed.
During 5th month
The first movements of the foetus and the appearance of hair on the head are usually observed.
By the end of 24 weeks
By the end of nine month (3rd trimester)
The body is covered with fine hair, eyelids separate (second trimester), and eyelashes are formed.
The foetus is fully developed and is ready for delivery.
Checkpoint
Q. Why is hCG a marker for early pregnancy detection in urine and blood tests?
Answer: hCG is produced only during pregnancy by the placenta shortly after implantation (a few days after fertilisation). It is detectable before a missed period. It increases rapidly in both blood and urine, allowing for sensitive detection methods.
TEST YOURSELF
1. The first movements of the human foetus are observed during (1) first month of pregnancy
(2) first trimester of pregnancy
(3) fifth month of pregnancy
(4) ninth month of pregnancy
2. Which of the following set of hormones are produced only during pregnancy time in women?
(1) hCG, hPL, oestrogen
(2) hCG, hPL, relaxin
(3) hCG, hPL, progestogen
(4) hCG, hPL, LH
3. Eyelids of the human foetus separate by the (1) end of second trimester
(2) end of third trimester
(3) end of first trimester
(4) end of first week
4. The placenta is connected to the embryo by (1) amnion
(2) umbilical cord
(3) allantois
(4) notochord
5. Placenta secretes all the following hormones, except
(1) hCG (2) hPL
(3) hGH (4) progesterone
6. Which of the following differentiates into embryonic ectoderm, endoderm and mesoderm?
(1) Trophoblast
(2) Inner cell mass
(3) Desidua capsularis
(4) Chorionic villi
Answer Key
(1) 3 (2) 2 (3) 1 (4) 2
(5) 3 (6) 2
2.7 PARTURITION AND LACTATION
Parturition marks the end of pregnancy with the delivery of the offspring, while lactation ensures the provision of vital nutrients through the mother’s milk.
2.7.1
Parturition (Childbirth)
Childbirth begins wit h labour, a series of strong, rhythmic uterine contractions that push the foetus and placenta out of the body. This process of childbirth, or the delivery of the foetus, is called parturition. Parturition is induced by a complex neuroendocrine mechanism involving cortisol, oestrogen and oxytocin.
Oestrogen increases the uterine sensitivity to oxytocin. Prostaglandins intensify uterine contractions and soften the cervix. Cortisol produced by the foetus promotes lung maturation and stimulates uterine contractions.
The decline in progesterone levels enables the uterus to respond to oxytocin and prostaglandins, promoting strong contractions for childbirth.
The signals for parturition originate from the fully developed foetus and the placenta, which induce mild uterine contractions called foetal ejection reflex.
Signals from the foetus include increased cortisol levels (a uterine stimulant) and pulmonary surfactant (which signals the readiness of the foetal lungs for breathing after birth). Signals from the placenta include reduced progesterone production, increased oestrogen production, and the release of prostaglandins. These combined signals contribute to the induction of the foetal ejection reflex.
The foetal ejection reflex triggers the release of oxytocin from the maternal pituitary. Oxytocin acts on the uterine muscle and causes stronger uterine contractions, which, in turn, stimulate further secretion of oxytocin. The stimulatory reflex between the uterine contractions and oxytocin secretion continues, resulting in increasingly stronger contractions. This leads to the expulsion of the baby out of the uterus through the birth canal.
Doctors may administer synthetic oxytocin to induce delivery. Pitocin is the brand name for a synthetic form of oxytocin,
Soon after the infant is delivered, the placenta, along with the decidua, is also expelled out of the uterus (afterbirth).
2.7.2 Lactation
One aspect of post-natal care unique to mammals is lactation, the production of mother’s milk. The mammary glands of the female undergo differentiation during pregnancy and start producing milk towards the end of pregnancy. Prolactin secreted by the anterior pituitary (Fig. 2.25) stimulates the mammary glands to produce milk. The ejection of milk is induced by oxytocin. This helps the mother in feeding the newborn.
The milk produced during the initial few days of lactation is called colostrum, which contains several antibodies (especially IgA) absolutely essential to protect newborn babies from initial sources of infections. Breast feeding during the initial period of infant growth is recommended by doctors for bringing up a healthy baby.
Fig. 2.25 Milk production and ejection
Checkpoint
Q. How can suckling by the first-born twin indirectly contribute to faster delivery of the second child?
Answer: Suckling stimulates the release of oxytocin.
CHAPTER REVIEW
■ The reproductive events in humans include gametogenesis, insemination, fertilistion, cleavage, blastulation, implantation, gestation and parturition.
■ Sperm formation continues even in older men, unlike in women.
The Male Reproductive System
■ The scrotum helps maintain the low temperature of the testes (2–2.5o C lower than the normal internal body temperature) necessary for spermatogenesis.
■ Each testis consists of approximately 250 testicular lobules, each containing one to three seminiferous tubules.
TEST YOURSELF
1. Oxytocin stimulates (1) parturition and milk secretion
(2) milk secretion and milk ejection
(3) implantation and parturition
(4) parturition and milk ejection
2. Colostrum is rich in (1) IgA antibodies
(2) IgG antibodies
(3) IgM antibodies
(4) IgE antibodies
3. Parturition is induced by a complex neuroendocrine mechanism promoted by all of the following hormones, except (1) cortisol
(2) progesterone
(3) oestrogen
(4) oxytocin
Answer Key (1) 4 (2) 1 (3) 2
■ Each seminiferous tubule is lined by male germ cells and Sertoli cells.
■ Sertoli cells provide nutrition to the germ cells.
■ Interstitial spaces contain Leydig cells that secrete androgens as well as immunologically competent cells.
■ The male sex accessory ducts include rete testis, vasa efferentia, epididymis and vas deferens.
■ The path of pa ssage of spermatozoa: Seminiferous tubules → Rete testis → Vasa efferentia → Epididymis → Vas deferens → Ejaculatory duct → Urethra → Vagina of the female.
■ The epididymis is located along the posterior surface of each testis.
■ Vas deferens and a duct from the seminal vesicle join to form an ejaculatory duct that opens into the urethra.
■ The urethra originates from the urinary bladder, extends through the penis and opens out by the urethral meatus.
■ Glans penis is the enlarged end of the penis covered by a loose fold of skin called prepuce (foreskin).
■ The male accessory glands include a pair of seminal vesicles, a prostate and a pair of bulbourethral glands.
■ Secretions of male accessory glands constitute the seminal plasma, which is rich in fructose, calcium and certain enzymes.
■ The secretions of bulbourethral glands help in the lubrication of the penis.
The Female Reproductive System
■ The female reproductive system consists of a pair of ovaries along with a pair of oviducts, uterus, cervix, vagina and external genitalia located in the pelvic region.
■ Ovaries are the primary female sex organs. They produce the female gametes and steroid ovarian hormones.
■ Each ovary is connected to the pelvic wall and uterus by ligaments.
■ Each ovary is covered by a thin epithelium which encloses the ovarian stroma.
■ The stroma is divided into two zones – a peripheral cortex and an inner medulla.
■ The oviducts (fallopian tubes), uterus and vagina constitute the female accessory ducts.
■ Each fallopian tube consists of three parts: infundibulum, ampulla and isthmus.
■ The funnel-shaped infundibulum bears finger-like fimbriae, which help in the
collection of the ovum.
■ Ampulla is the site of fertilisation.
■ The isthmus has a narrow lumen, and it joins the uterus.
■ The uterus (womb) is like an inverted pear supported by ligaments attached to the pelvic wall.
■ The uterus opens into the vagina through a narrow cervix.
■ The cervical canal, along with the vagina, forms the birth canal.
■ The wall of the uterus has three layers of tissue: outer perimetrium, middle myometrium, inner endometrium.
■ The external thin membranous perimetrium, middle thick layer of smooth muscle, myometrium and inner glandular layer called endometrium that lines the uterine cavity.
■ The glandular endometrium undergoes cyclical changes during the menstrual cycle.
■ The thick layer of smooth muscle, the myometrium, exhibits strong contraction during parturition.
■ The female external genitalia include mons pubis, labia majora, labia minora, hymen and clitoris.
■ Mons pubis is a cushion of fatty tissue covered by skin and pubic hair.
■ The labia majora are fleshy folds of tissue that extend down from the mons pubis and surround the vaginal opening.
■ The labia minora are paired folds of tissue under the labia majora.
■ The opening of the vagina is often covered partially by a membrane called the hymen.
■ The presence or absence of hymen is not a reliable indicator of virginity or sexual experience.
■ The clitoris is a tiny finger-like structure that lies at the upper junction of the two labia minora above the urethral opening.
■ The glandular tissue of each breast is divided into 15-20 mammary lobes containing clusters of cells called alveoli that secrete milk.
■ The path of flow of milk in the mammary gland: alveoli, mammary tubules, mammary duct, mammary ampulla, lactiferous duct.
Gametogenesis
■ The sequence of stages during spermatogenesis: spermatogonia (2n) → primary spermatocytes (2n) → secondary spermatocytes (n) → spermatids (n), spermatozoa (n).
■ Spermatogenesis begins at puberty.
■ Spermatogonia undergo mitosis. Primary spermatocyte undergoes meiosis I. Secondary spermatocyte undergoes meiosis II.
■ One primary spermatocyte produces four equal haploid spermatids.
■ The spermatids are transformed into spermatozoa by a process called spermiogenesis.
■ Spermiation is the release of spermatozoa from Sertoli cells into the lumen of seminiferous tubules.
■ Spermatogenesis starts at the age of puberty due to a significant increase in the levels of GnRH, a hypothalamic hormone.
■ GnRH stimulates the secretion of FSH and LH.
■ LH stimulates Leydig cells to synthesise and secrete androgens, which stimulate spermatogenesis.
■ FSH stimulates Sertoli cells to secrete some factors which help in spermiogenesis.
■ A sperm is composed of a head, neck, a middle piece and a tail.
■ The sperm head contains the nucleus and acrosome.
■ The acrosomal enzymes help in fertilisation.
■ The middle piece possesses numerous mitochondria.
■ A human male ejaculates about 200 to 300 million sperm during coitus.
■ For normal fertility, it is essential that at least 60 per cent of these sperm exhibit normal shape and size, and at least 40 per cent of them show vigorous motility.
■ Secretions of the epididymis, vas deferens, seminal vesicle and prostate are essential for the maturation and motility of sperm.
■ The seminal plasma, along with the sperm, constitutes the semen.
■ Androgens maintain the functions of male sex accessory ducts and glands.
■ Oogenesis is markedly different from spermatogenesis.
■ Oogenesis is initiated during the embryonic development stage.
■ Two million oogonia are formed within each foetal ovary. No more oogonia are formed after birth.
■ Primary oocytes are arrested at prophase-I till puberty.
■ A primary follicle contains a primary oocyte surrounded by a layer of granulosa cells.
■ A large number of primary follicles degenerate during the phase from birth to puberty.
■ At puberty, only 60,000 to 80,000 primary follicles are left in each ovary.
■ A secondar y follicle contains a primary oocyte surrounded by several layers of granulosa cells and theca.
■ A tertiary follicle is characterised by a fluidfilled cavity called antrum.
■ The theca in a tertiary follicle is organised into inner theca and theca externa.
■ Meiosis I during oogenesis is an unequal division resulting in the formation of a large haploid secondary oocyte and a tiny first polar body.
■ A mature follicle with a secondary oocyte (surrounded by zona pellucida) and first polar body is called a Graafian follicle.
■ Ovulation is the release of the secondary oocyte from the Graafian follicle.
Menstrual
Cycle
■ The menstrual cycle is the reproductive cycle in female primates (e.g. monkeys, apes and human beings).
■ Menstrual cycles occur from menarche (puberty) to menopause (50 years).
■ The typical length of the human menstrual cycle is either 28 or 29 days.
■ The menstrual phase is the first phase of the menstrual cycle, and it lasts for 3-5 days.
■ The menstrual flow results due to the breakdown of the endometrial lining of the uterus.
■ Lack of menstruation may be indicative of pregnancy. It may also be caused due to some other causes.
■ During this follicular phase, the primary follicles in the ovary grow to become a fully mature Graafian follicle.
■ During the follicular phase, the uterus regenerates through proliferation under the influence of oestrogens.
■ The LH and FSH levels increase gradually during the follicular phase and peak on the 14th day.
■ LH surge induces ovulation.
■ During the luteal phase, the remaining parts of the Graafian follicle transform into the corpus luteum.
■ The corpus luteum secretes large amounts of progesterone, which is essential for the maintenance of the endometrium.
■ During pregnancy, all events of the menstrual cycle stop, and there is no menstruation.
■ In the absence of fertilisation, the corpus luteum degenerates, leading to the disintegration of the endometrium which results in menstruation.
Fertilisation and Implantation
■ Fertilisation can only occur if the ovum and sperm are transported simultaneously to the ampullary region.
■ The secretions of the acrosome help the sperm enter into the cytoplasm of the ovum through the zona pellucida and the plasma membrane.
■ Changes in the plasma membrane of the oocyte block the entry of additional sperm.
■ Entry of sperm induces the completion of the meiotic division of the secondary oocyte.
■ The second meiotic division is also unequal and results in the formation of a second polar body and a haploid ovum.
■ The zygote carrying XX would develop into a female baby, and the one carrying XY would form a male.
■ The embryo with 8 to 16 blastomeres is called a morula.
■ The morula transforms into a blastocyst as it moves further into the uterus.
■ The blastocyst has an outer layer of cells called trophoblast and an inner group of cells called the inner cell mass.
■ The trophoblast layer gets attached to the endometrium.
■ The inner cell mass gets differentiated as the embryo.
Pregnancy and Embryonic Development
■ After implantation, chorionic villi and uterine tissue become interdigitated with each other and jointly form the placenta.
■ The placenta is connected to the embryo through an umbilical cord, which helps in the transport of substances to and from the embryo.
■ The placenta produces several hormones like hCG, hPL, oestrogens, progestogens, etc.
■ In the later phase of pregnancy, a hormone called relaxin is also secreted by the ovary.
■ hCG, hPL and relaxin are produced in women only during pregnancy.
■ During pregnancy, the levels of other hormones like oestrogens, progestogens, cortisol, prolactin, thyroxine, etc., are increased several folds in the maternal blood.
■ Increased production of these hormones is essential for supporting foetal growth, metabolic changes in the mother and maintenance of pregnancy.
■ After implantation, the inner cell mass differentiates into ectoderm and endoderm. A mesoderm soon appears.
■ The inner cell mass contains certain cells called stem cells, which have the potency to give rise to all the tissues and organs.
■ In human beings, after one month of pregnancy, the embryo’s heart is formed.
■ The first sign of a growing foetus may be noticed by listening carefully to the heart sound through the stethoscope.
■ By the end of the second month of pregnancy, the foetus develops limbs and digits.
■ By the end of 12 weeks (first trimester), most of the major organ systems are formed (e.g., limbs and external genitalia).
■ The first movements of the foetus and the appearance of hair on the head are usually observed during the fifth month.
■ By the end of about 24 weeks (end of the second trimester), the body is covered with fine hair, eyelids are separated, and eyelashes are formed.
Parturition and Lactation
■ A complex neuroendocrine mechanism induces parturition.
■ The signals for parturition originate from the fully developed foetus and the placenta, which induce mild uterine contractions called foetal ejection reflex.
■ The foetal ejection reflex triggers the release of oxytocin from the maternal pituitary.
■ Oxytocin stimulates uterine contractions.
■ Soon after the infant is delivered, the placenta is also expelled out of the uterus.
■ The mammary glands of the female undergo differentiation during pregnancy and start producing milk towards the end of pregnancy.
■ The milk produced during the initial few days of lactation is called colostrum.
■ Colostrum contains several antibodies (esp. IgA) essential to develop resistance in newborn babies.
NEET DRILL
The Male Reproductive System
1. Which one of the following is true with regard to human reproduction?
(1) Gametogenesis starts at birth in males.
(2) Females can continue producing gametes even at old age.
(3) Males are capable of producing gametes even at old age.
(4) Gametogenesis begins after menarche in females.
2. Which of the following is common to male reproductive system and urinary system?
(1) Ureter (2) Vas deferens
(3) Urethra (4) Ejaculatory duct
3. Which of the following structures in the human male reproductive system is unpaired?
(1) Vas deferens
(2) Bulbourethral gland
(3) Prostate gland
(4) Seminal vesicle
4. If vasa efferentia gets blocked, the gametes will not be transported from
(1) testis to epididymis
(2) epididymis to vas deferens
(3) vas deferens to ejaculatory duct
(4) ejaculatory duct to urethra
5. Which of the following gland is not seen in the male reproductive system?
(1) Seminal vesicle
(2) Prostate gland
(3) Bulbourethral gland
(4) Bartholin’s gland
6. In human testes, seminiferous tubules and vasa efferentia are connected by
(1) epididymis
(2) vas deferens
(3) ejaculatory duct
(4) rete testis
7. Which of the following is not an accessory duct in the male reproductive system?
(1) Vasa deferens
(2) Epididymis
(3) Seminiferous tubule
(4) Vasa efferentia
8. Seminal plasma in humans is rich in which of the following?
(a) Glucose
(b) Fructose
(c) Calcium
(d) Enzymes
(1) Only (a)
(2) Only (b) and (c)
(3) Only (b), (c) and (d)
(4) Only (c) and (d)
The Female Reproductive System
9. The part of the fallopian tube that joins the uterus is
(1) ampulla (2) isthmus
(3) infundibulum (4) cervix
10. Which of the following is a correct description of labia majora?
(1) Paired folds of tissue under the labia minora
(2) Tiny finger-like structures above the urethral opening
(3) Fleshy folds of tissue surrounding the vaginal opening
(4) Membrane which partially covers the opening of the vagina
11. Which of the following sweep the ovulated egg into fallopian tube?
(1) Labia (2) Ligaments
(3) Fimbriae (4) Rugae
12. Mark the correct statement about the endometrium.
(1) It undergoes strong contractions during the child birth.
(2) It is the external membranous layer of the uterine wall.
(3) It undergoes cyclical changes during menstrual cycle.
(4) It is the middle muscular layer of the uterine wall.
13. Ovaries produce all the following, except (1) inhibin (2) oestrogens
(3) FSH (4) progesterone
14. The endometrium is the lining of the (1) uterus (2) vagina
(3) fallopian tube (4) vestibule
15. The clusters of milk-secreting cells of the mammary glands are termed (1) alveoli (2) tubules
(3) fascicles (4) ampullae
Gametogenesis
16. FSH acts on the Sertoli cells and stimulates the secretion of some factors which help in the process of
(1) capacitation
(2) fertilisation
(3) spermiogenesis
(4) parturition
17. Which of the following statements is not true?
(1) Spermatogenesis occurs in the seminiferous tubules of the testes.
(2) Spermatogenesis continues even in old men.
(3) Spermatogenesis is initiated during embryonic stage.
(4) Spermatogenesis is controlled by hormones.
18. At least _____ of sperms should have normal shape for normal fertility.
(1) 10% (2) 30%
(3) 60% (4) 20%
19. Which of the following undergoes mitosis?
(1) Primary spermatocyte
(2) Spermatid
(3) Secondary spermatocyte
(4) Spermatogonium
20. Which of the following undergoes meiosis I?
(1) First polar body
(2) Primary oocyte
(3) Secondary oocyte
(4) Oogonium
21. Select the correct sequence of stages in oogenesis.
22. The second meiotic division during spermatogenesis produces (1) spermatogonia
(2) secondary spermatocytes
(3) spermatozoa (4) spermatids
23. Head of sperm contains (1) haploid nucleus
(2) diploid nucleus
(3) mitochondria
(4) axoneme
24. Semen consists of the secretions of all the following, except
(1) prostate gland
(2) seminal vesicles
(3) Bartholin’s glands
(4) bulbourethral glands
25. Sertoli cells are regulated by the pituitary hormone
(1) FSH (2) GH
(3) prolactin (4) LH
26. FSH stimulates which of the following cells to secrete some factors that help in the process of spermatogenesis?
(1) Leydig cells (2) Sertoli cells
(3) Paneth cells (4) Kupffer cells
27. The number of chromosomes in the first polar body formed during oogenesis in female humans is
(1) 46 (2) 23
(3) 44 (4) 22
28. Select the correct match.
(1) Spermiation - Transfer of sperms into the female genital tract
(2) Implantation - The delivery of the baby
(3) Spermiogenesis - Transformation of spermatids into spermatozoa
(4) Capacitation - Blockage of additional sperms from penetrating the oocyte
29. Select the correct match of a hormone and its source.
(1) LH – Corpus luteum
(2) Testosterone – Sertoli cells
(3) GnRH – Adenohypophysis
(4) Oestrogen – Graafian follicle
Menstrual Cycle
30. Select the incorrect statement.
(1) The reproductive cycle in the female primates is called menstrual cycle.
(2) Menarche is the first onset of menstruation.
(3) Menopause is the permanent cessation of menses.
(4) Lack of menstruation is a certain indicator of pregnancy.
31. Which of the following is not associated with ovulatory phase of menstrual cycle?
(1) High GnRH pulse frequency
(2) LH surge
(3) High levels of oestrogen
(4) High levels of progesterone
32. Which of the following options correctly represents the plasma concentrations of pituitary and ovarian hormones around the time of ovulation?
FSH LH Oestrogen Proges terone
(1) High High High Low
(2) High High Low Low
(3) Low High Low High
(4) Low Low High High
33. Which is correctly matched in a normal 28-day menstrual cycle?
(1) Endometrium regenerates – 5 th to 10th day
(2) Release of egg – 5th day
(3) Endometrium secretes nutrients for implantation – 11th to 14th day
(4) Rise in progesterone level – 1st to 15th day
Fertilisation and Implantation
34. At what stage does the human embryo attach to the uterine wall?
(1) Morula (2) Blastocyst
(3) Gastrula (4) Zygote
35. The sex of the baby is determined at the time of
(1) gametogenesis depending on the type of allosome of the sperm
(2) gametogenesis depending on the type of allosome of the ovum
(3) fertilisation depending on the type of allosome of the sperm
(4) fertilisation depending on the type of allosome of the ovum
36. The layer of the blastocyst that gets attached to the endometrium during implantation is (1) epiblast (2) trophoblast (3) hypoblast (4) inner cell mass
37. The number of chromosomes in the human zygote is (1) 46 (2) 23 (3) 45 (4) 22
38. In the female reproductive tract, morula stage is formed (1) after the embryo enters the uterus (2) after implantation (3) in the fallopian tube (4) before cleavage
39. Fertilisation in humans can occur only if (1) sexual intercourse takes place on the day of ovulation
(2) the ovum and sperm are transported to the ampullary region simultaneously (3) the oocyte has completed second meiotic division before ovulation
(4) ovum is transported to the vagina that receives sperm during coitus
Pregnancy and Embryonic Development
40. The fifth month of the foetus is marked by (1) separation of eye lids (2) formation of eye lashes (3) appearance of hair on head (4) beginning of the heart beat
41. What is common between the corpus luteum and the placenta?
FURTHER EXPLORATION
1. Cowper’s gland is located (1) below the prostate gland (2) in the abdominal cavity (3) under the prepuce (4) above the urinary bladder
2. Select the correct sequence of layers around a mature ovum inside-out.
(1) Both are formed from the remnants of Graafian follicle
(2) Both serve as temporary endocrine glands
(3) Both secrete hCG and hPL
(4) Both are composed of maternal tissue and foetal tissue
42. In human beings, by the end of the second month of pregnancy,
(1) the foetus develops limbs and digits
(2) the first movements of the foetus
(3) the body is covered with lanugo (fine hair)
(4) the foetal heart is yet to produce heart sounds
Parturition and Lactation
43. Which of the following hormones does not promote parturition?
(1) Cortisol (2) Progesterone
(3) Oestrogen (4) Oxytocin
44. For the newborn, colostrum is an important source of
(1) digestive enzymes
(2) oxygen
(3) clotting factors
(4) antibodies
45. The foetal ejection reflex in human triggers the release of
(1) oxytocin from paternal pituitary
(2) relaxin from foetal ovary
(3) oxytocin from maternal pituitary
(4) human chorionic gonadotropin from placenta
(1) Perivitelline space, corona radiata, oolemma, zona pellucida
(2) Corona radiata, oolemma, perivitelline space, zona pellucida
(3) Oolemma, perivitelline space, zona pellucida, corona radiata
(4) Oolemma, perivitelline space, corona radiata, zona pellucida
3. The column of the penis through which urethra passes is (1) corpus luteum
(2) corpus callosum
(3) corpus cavernosum
(4) corpus spongiosum
4. Eggs of human are (1) alecithal
(2) megalecithal
(3) cleidoic
(4) mesolecithal
5. During a typical menstrual cycle, progesterone level peaks only once, but 2 peaks of oestrogen can be observed on (1) 12th day and 21st day
(2) 5th day and 9th days
(3) 3rd day and 28th day
(4) 1st day and 28th day
6. The fibrous external layer of the testis is
(1) tunica vaginalis
(2) tunica albuginea
(3) tunica adventitia
(4) tunica intima
7. Which of the following is a female accessory gland?
(1) Rectal glands
(2) Prostate gland
(3) Bartholin’s glands
(4) Cowper’s glands
8. A bulk of semen is secreted by (1) seminal vesicles.
(2) prostate gland.
(3) bulbourethral glands.
(4) Bartholin’s glands.
9. In a 30-day menstrual cycle, ovulation occurs on
(1) 16th day
(2) 15th day (3) 14th day
(4) 17th day
10. During f ertilisation, only one sperm can penetrate the oocyte. The entry of additional sperms is blocked by
(1) depolarisation of the cell membrane of the oocyte
(2) secretion of enzymes from acrosome (3) capacitation of spermatozoa
(4) fusion of pronuclei of sperm and ovum
11. The clitoris of the female reproductive system is homologous to (1) prostate gland of male (2) penis of male
(3) seminal vesicle of male (4) testis of male
12. Mark the incorrect statement about testis. (1) It is the site of maturation and capacitation of the sperm.
(2) It is both a primary sex organ and an endocrine structure.
(3) It is oval in shape and is covered by a dense covering.
(4) It has many compartments called testicular lobules.
13. Prepuce is a loose fold of skin covering the (1) testis
(2) vaginal orifice
(3) scrotum
(4) glans penis
14. Androgen binding protein is produced by (1) Paneth cells
(2) Sertoli cells
(3) Goblet cells
(4) Leydig cells
15. Failure of descent of testes into the scrotum is termed (1) hydroceol
(2) inguinal hernia
(3) cryptorchidism
(4) erectile dysfunction
16. During spermiogenesis, acrosome is formed from
(1) golgi body
(2) endoplasmic reticulum
(3) vacuole
(4) ribosome
17. Centrioles of sperm are located in the (1) head (2) neck
(3) middle piece (4) tail
18. Zona pellucida is digested by (1) acrosin
(2) hyaluronidase
(3) lysozyme
(4) carbonic anhydrase
19. Bartholin’s glands are homologous to (1) rectal glands
(2) inguinal glands
(3) prostate glands
(4) Cowper’s glands
20. The female reproductive cycle in nonprimate mammals is termed (1) oestrous cycle (2) menstrual cycle
MATCHING TYPE QUESTIONS
1. Match Column-I with Column-II.
Column-I Column-II
(A) Seminiferous tubules (I) Sperm maturation
(B) Epididymis (II) Secretion of androgens
(C) Leydig cells (III) Spermatogenesis
(D) Bulbourethral glands (IV) Lubrication of penis
Select the correct option.
(A) (B) (C) (D)
(1) I III II IV
(2) III I II IV
(3) III I IV II
(4) IV II I III
(3) Cori’s cycle (4) Kreb’s cycle
21. Capacitation refers to the activation of the (1) female gamete in the male reproductive tract
(2) female gamete in the female reproductive tract
(3) male gamete in the female reproductive tract
(4) male gamete in the male reproductive tract
22. Which of the following is not a function of Sertoli cells?
(1) Secretion of inhibin
(2) Nourishment of germ cells
(3) Secretion of ABP
(4) Secretion of testosterone
23. The type of placenta in humans is (1) hemochorial
(2) hemoendothelial
(3) epitheliochorial
(4) syndesmochorial
2. Match Column-I with Column-II. Column-I (Parts of sperm) Column-II
(A) Head (I) Energy
(B) Neck (II) Motility
(C) Tail (III) Centriole
(D) Middle piece (IV) Acrosome
Select the correct option.
(A) (B) (C) (D)
(1) IV II III I
(2) III IV II I
(3) IV III II I
(4) IV III I II
3. Match Column-I with Column-II.
Column-I Column-II
(A) Milk synthesising hormone (I) Progesterone
(B) Pregnancy hormone (II) LH
(C) Milk letdown hormone (III) Prolactin
(D) Formation of corpus luteum (IV) Oxytocin
Select the correct option.
(A) (B) (C) (D)
(1) I III II IV
(2) III IV II I
(3) III I IV II
(4) III IV I II
4. Match Column-I with Column-II.
Column-I Column-II
(A) Secretory phase (I) Maturation of follicle
(B) Proliferative phase (II) Development of corpus luteum
(C) Menstruation (III) Breakdown of endometrial lining
Select the correct option.
(A) (B) (C)
(1) III I II
(2) II III I
(3) II I III
(4) I II III
5. Match Column-I with Column-II.
Column-I Column-II
(A) Morula (I) Outer layer of blastocyst
(B) Trophoblast (II) Results in the formation of ootid
(C) Second meiotic division (III) Embryo with 8-16 blastomeres
(D) Inner cell mass (IV) Differentiates as the embryo
Select the correct option.
(A) (B) (C) (D)
(1) III I IV II
(2) I III II IV
(3) II IV III I
(4) III I II IV
6. Match Column-I with Column-II.
Column-I Column-II
(A) Fimbriae (I) Menstruation
(B) Endometrium (II) Capture of ovum
(C) Ovaries (III) Primary sex organs
(D) Clitoris (IV) External genitalia
Select the correct option.
(A) (B) (C) (D)
(1) IV II III I
(2) II I III IV
(3) I III II IV
(4) II III I IV
STATEMENT TYPE QUESTIONS
Each question has two statements: statement I (S-I) and statement II (S-II). Mark the correct answer as
(1) if both statement I and statement II are correct
(2) if both statement I and statement II are incorrect
(3) if statement I is correct but statement II is incorrect
(4) if statement I is incorrect but statement II is correct
1. S-I : The testes in male humans are situated outside the abdominal cavity within a pouch called the scrotum.
S-II : The scrotum helps in maintaining the high temperature of the testes necessary for spermatogenesis.
2. S-I : Each testis of a male human has about 250 compartments called testicular lobules.
S-II : Each lobule contains one to three highly coiled uriniferous tubules.
3. S-I : The sperm head contains an elongated diploid nucleus covered by a cap-like structure, acrosome.
S-II : The acrosome is filled with enzymes that help in the fertilisation of the ovum.
4. S-I : After implantation, chorionic villi and uterine tissue become interdigitated with each other and jointly form a placenta.
S-II : The placenta is connected to the embryo through an umbilical cord which helps in the transport of substances to and from the embryo.
5. S-I : The infundibulum of the fallopian tube bears finger-like projections called villi.
S-II : The infundibulum has a narrow lumen and joins the uterus.
6. S-I : The menstrual flow results from the breakdown of the myometrial lining of the uterus.
S-II : LH surge triggers menstruation.
7. S-I : The glandular tissue of each breast is divided into 15-20 mammary alveoli.
S-II : The mammary alveoli are clusters of cells that secrete and store milk.
8. S-I : Soon after the infant is delivered, the placenta is also expelled out of the uterus.
S-II : The mammary glands of the female undergo differentiation during pregnancy and start producing milk towards the end of pregnancy.
9. S-I : The interstitial spaces between the seminiferous tubules contain Sertoli cells.
S-II : Other immunologically competent cells are also present in the interstitial spaces.
10. S-I : Changes in the levels of pituitary hormones induce changes in the ovary.
S-II : Changes in the levels of ovarian hormones induce changes in the uterus.
11. S-I : The male accessory glands include paired seminal vesicles, unpaired prostate and paired bulbourethral glands.
S-II : Secretions of male accessory glands constitute the seminal plasma, which is rich in glucose, calcium and certain enzymes.
12. S-I : Immediately after implantation, trophoblast differentiates into ectoderm and endoderm.
S-II : These two layers give rise to all tissues (organs) in adults.
13. S-I : The primary oocyte undergoes meiosis II, resulting in the formation of a secondary oocyte and the first polar body.
S-II : Meiosis II of oogenesis is an unequal reductional division.
14. S-I : The perimetrium undergoes cyclical changes during the menstrual cycle.
S-II : The endometrium exhibits strong contraction during the delivery of the baby.
15. S-I : The first sign of a growing foetus may be noticed by listening to the heart sound carefully through the stethoscope.
S-II : In human beings, the embryo’s heart is formed after one trimester of pregnancy.
16. S-I : FSH acts on the Sertoli cells and stimulates the secretion of some factors that help in the process of spermiogenesis.
S-II : Spermiogenesis involves the development of the sperm tail and the reduction of excess cytoplasm.
ASSERTION AND REASON QUESTIONS
In each of the following questions, a statement of Assertion (A) is given, followed by a corresponding statement of Reason (R). Mark the correct answer as
(1) if both (A) and (R) are true and (R) is the correct explanation of (A)
(2) if both (A) and (R) are true but (R) is not the correct explanation of (A)
(3) if (A) is true but (R) is false
(4) if both (A) and (R) are false
1. (A) : D uring pregnancy, all events of the menstrual cycle stop, and there is no menstruation.
(R) : In the absence of fertilisation, the
17. S-I : The cleavage starts while the zygote moves through the isthmus of the oviduct towards the uterus.
S-II : The morula continues to divide and transforms into the blastocyst as it moves further into the uterus.
18. S-I : A primary spermatocyte undergoes the first meiotic division, leading to the formation of two equal, haploid secondary spermatocytes.
S-II : Four haploid spermatids are formed from each secondary spermatocyte.
19. S-I : The absence of hymen is a reliable indicator of virginity.
S-II : The absence of menstruation is a reliable indication of pregnancy.
20. S-I : The human male ejaculates about 200 to 300 billion sperms during coitus.
S-II : For normal fertility, at least 60 per cent of these sperms must have normal shape and size, and at least 40 per cent of them must show vigorous motility.
corpus luteum degenerates.
2. (A) : Sperm motility is crucial for normal fertility.
(R) : For normal fertility, at least 90 per cent of the ejaculated sperm must show vigorous motility.
3. (A) : Penis and clitoris are homologous.
(R) : Both serve as a passageway for urine and semen.
4. (A) : Ovulation around the 14 th day of a 28-day menstrual cycle.
(R) : FSH attains a peak level around the 14th day of a 28-day menstrual cycle.
5. (A) : The failure of the descent of the testes into the scrotum can result in sterility.
(R) : The testes require a slightly lower temperature than the body for spermatogenesis.
6. (A) : The presence or absence of a hymen is a very reliable indicator of virginity.
(R) : The hymen is always torn during the first coitus (intercourse).
7. (A) : Myometrium exhibits strong contractions during the delivery of the baby.
(R) : Skeletal muscles are capable of powerful contractions.
8. (A) : Androgens are responsible for the secondary sexual characteristics in men.
(R) : Androgens play a crucial role in the initiation and progression of spermatogenesis.
9. (A) : The primary oocyte is haploid.
(R) : An oogonium undergoes meiosis I to produce a primary oocyte.
10. (A) : The endometrium undergoes cyclical changes during the menstrual cycle.
(R) : The endometrium proliferates during the menstrual phase and disintegrates during the luteal phase.
11. (A) : Meiosis I of oogenesis results in the formation of a large secondary oocyte and a tiny first polar body.
(R) : Meiosis I of oogenesis is a reductional division.
12. (A) : Without undergoing spermiation, sperm cannot be transported to the epididymis.
(R) : Before spermiation, sperm heads are embedded in Sertoli cells.
13. (A) : Male accessory ducts store and transport the sperms.
(R) : The functions of male sex accessory ducts and glands are maintained by the androgens.
14. (A) : During pregnancy, the levels of oestrogens, progestogens, cortisol, prolactin, thyroxine, etc., are increased severalfold in the maternal blood.
(R) : Increased production of these hormones is essential for supporting fetal growth, metabolic changes in the mother and the maintenance of pregnancy.
15. (A) : Spermatogenesis starts at the age of puberty.
(R) : At puberty, the hypothalamus begins to release increasing amounts of GnRH.
16. (A) : The inner cell mass gives rise to the embryo proper.
(R) : The inner cell mass contains stem cells, which have the potency to give rise to all tissues and organs.
17. (A) : The vagina is a part of the birth canal through which a baby passes during childbirth.
(R) : The vagina is the receptacle of the penis during coitus.
18. (A) : The number of ovarian follicles in a female foetus is much higher than the number of follicles at puberty.
(R) : Follicular atresia reduces the ovarian follicle count over time, and many follicles degenerate before reaching puberty.
19. (A) : During pregnancy, there is no menstruation.
(R) : During pregnancy, progesterone and oestrogen levels remain elevated.
20. (A) : In the ab sence of fertilisation, progesterone and oestrogen levels decline.
(R) : In the absence of fertilisation, the corpus luteum disintegrates.
21. (A) : The sperm head plays a crucial role in the locomotion of sperm to the site of fertilisation.
(R) : The sperm head contains mitochondria that generate ATP, the energy currency
BRAIN TEASERS
1. The uterus is in which phase of the menstrual cycle during the implantation of the blastocyst?
(1) Menstrual phase
(2) Proliferative phase
(3) Ovulatory phase
(4) Secretory phase
2. The female reproductive cycle encompasses the ovarian and uterine cycles. Select the incorrect statement about a woman having normal and regular periods.
(1) The ovarian cycle and uterine cycle are of the same duration.
(2) The ovarian cycle and uterine cycle are synchronised.
(3) The ovarian cycle is dependent on the uterine cycle.
(4) The uterine cycle is dependent on the ovarian cycle.
3. Select the option that correctly describes the features of spermatogenesis and oogenesis.
(1)
SG No No Yes Yes
OG No Yes Yes No
needed for sperm movement.
22. (A) : Changes in the plasma membrane of the ovum that occur during fertilisation block the entry of additional sperms.
(R) : Acrosomal enzymes help the sperm enter the cytoplasm of the ovum.
23. (A) : At menopause, the levels of oestrogen and progesterone increase.
(R) : At menopause, the levels of FSH and LH decrease.
(2)
(3)
(4)
SG Yes No Yes Yes
OG No Yes Yes No
SG No Yes No No
OG Yes No Yes Yes
SG Yes No Yes Yes
OG No Yes No No
SG = Spermatogenesis; OG = Oogensis
4. Study the following graph showing the levels of pituitary and ovarian hormones during the menstrual cycle and select the correct explanation for the labels A, B, C and D.
(1) B initiates regeneration of endometrium, while D causes further development.
(2) A and B are gonadotropins, whereas C and D are ovarian hormornes.
(3) Combinations of B and C are used as oral contraceptive pills.
(4) A is oestrogen, whereas D is progesterone.
FLASHBACK (Previous NEET Questions)
1. Match List I with List II relating to human female external genitalia. (2024–R)
List I List II
(A) Mons pubis (I) A fleshy fold of tissue surrounding the vaginal opening
(B) Clitoris (II) Fatty cushion of cells covered by skin and hair
(2) Vasa efferentia→ Rete testis→ Vas deferens →Epididymis
(3) Rete testis →Vasa efferentia →Epididymis → Vas deferens
(4) Rete testis →Epididymis →Vasa efferentia → Vas deferens
7. Ejaculatory duct is formed by the union of (1) cervical canal and vagina
(2) vas deferens and duct from the seminal vesicle
(3) epididymis and duct from the cowper’s gland
(4) vas deferens and urethra
8. Seminal plasma is rich in all the following, except
(1) calcium (2) fructose
(3) glucose (4) enzymes
9. Match Column-I with Column-II.
Column-I
Column-II
(A) Infundibulum (I) External genitalia
(B) Uterus (II) Fimbriae
(C) Mons pubis (III) Site of fertilisation
(D) Ampulla (IV) Endometrium
Select the correct option.
(A) (B) (C) (D)
(1) I III IV II
(2) II IV I III
(3) IV I II III
(4) III I IV II
10. The human ovary is connected by ligaments to the
(1) pelvic wall and uterus
(2) uterus and vagina
(3) pelvic wall and diaphragm
(4) kidneys and uterus
11. The function of ovary is
(a) To produce female gamete
(b) To provide the site for fertilisation
(c) To provide the site for implantation
(d) To produce several steroid hormones
(1) a and b
(2) a, b and d
(3) a, b and c
(4) a and d
12. Given below are two statements. One is labelled Assertion (A) and the other is labelled Reason (R).
Assertion (A) : The uterus exhibits strong contractions during the delivery of a baby.
Reason (R) : The thick middle layer of the uterine wall is made up of involuntary striped muscles.
In light of the above statements, choose the correct answer from the options given below.
(1) Both (A) and (R) are true and (R) is the correct explanation of (A).
(2) Both (A) and (R) are true but (R) is not the correct explanation of (A).
(3) (A) is true but (R) is false.
(4) Both (A) and (R) are false.
13. Given below are two statements. One is labelled as Assertion (A) and the other is labelled as reason (R).
Assertion (A) : Fimbriae are the fingerlike projections formed by the edges of the infundibulum of fallopian tube.
Reason (R) : The fimbriae help in collection of fertilised ova.
In the light of the given statements, choose the correct answer from the options given.
(1) Both (A) and (R) are true and (R) is the correct explanation of (A).
(2) Both (A) and (R) are true but (R) is not the correct explanation of (A).
(3) (A) is true but (R) is false.
(4) Both (A) and (R) are false.
14. The clitoris is a tiny finger-like structure which lies at the
(1) lower junction of the two labia majora below the urethral opening
(2) upper junction of the two labia majora below the urethral opening
(3) upper junction of the two labia minora above the urethral opening
(4) lower junction of the two labia minora above the urethral opening
15. Mark the correct statement about hymen.
(1) It is always torn after first coitus.
(2) Presence of it is a reliable indicator of virginity.
(3) It is a membrane that completely covers the vaginal orifice.
(4) It can be torn by a sudden fall or a jolt.
16. Which of the following sets represents some of the external genitalia of a human female?
(1) Labia majora, labia minora, oviduct
(2) Labia minora, clitoris, vagina
(3) Clitoris, labia majora, vagina
(4) Labia majora, labia minora, clitoris
17. In a functional breast, milk is temporarily stored in
(1) mammary duct
(2) mammary alveoli
(3) mammary tubule
(4) lactiferous duct
18. Milk secreted from the cells of alveoli of mammary lobes reaches the nipple through lactiferous duct (L), mammary duct (D), mammary tubule (T) and mammary ampulla
(A) in which order?
(1) TDAL (2) DTLA
(3) DTAL (4) ATDL
19. Select the incorrect match.
(1) Uterine wall - Endometrium, myometrium, and perimetrium
(2) Fallopian tube - Infundibulum, ampulla,
and isthmus
(3) Male accessory glands - Prostate, seminal vesicles, and bulbourethral glands
(4) Female external genitalia - Hymen, clitoris, and vagina
20. A primary spermatocyte divides to form
(1) two equal-sized haploid secondary spermatocytes
(2) two equal-sized diploid secondary spermatocytes
(3) two unequal-sized haploid secondary spermatocytes
(4) two unequal-sized diploid secondary spermatocytes
21. Which of the following best describes spermiogenesis?
(1) Release of sperm into lumen of seminiferous tubules
(2) Formation of spermatozoa from spermatogonium
(3) Release of semen into the vagina
(4) Maturation of spermatid into spermatozoan
22. The function of Sertoli cells is controlled by (1) oestrogen (2) FSH
(3) testosterone (4) LH
23. The functions of male sex accessory ducts and glands are maintained by (1) FSH
(2) androgens
(3) TSH
(4) oestrogens
24. The number of chromosomes in oogonium, primary oocyte, secondary oocyte, ovum and zygote in human beings are respectively
(1) 46, 46, 23, 23 and 46
(2) 46, 23, 23, 23 and 46
(3) 46, 46, 23, 23 and 23
(4) 46, 46, 46, 23 and 46
25. Which of the following is the longest phase in oogenesis?
(1) Prophase I (2) Metaphase I
(3) Prophase II
(4) Metaphase II26. Identify the correct sequence of stages in oogenesis.
27. Given below are two statements. One is labelled Assertion (A) and the other is labelled Reason (R).
Assertion (A) : Lack of menstruation is not always indicative of pregnancy.
Reason (R) : Lack of menstruation can be caused due to some other causes like stress, poor health etc.
In light of the above statements, choose the correct answer from the options given below.
(1) Both (A) and (R) are true and (R) is the correct explanation of (A).
(2) Both (A) and (R) are true but (R) is not the correct explanation of (A).
(3) (A) is true but (R) is false.
(4) Both (A) and (R) are false.
28. Ovulation in human females is stimulated by
(1) low levels of oestrogen and high levels of LH
(2) high levels of oestrogen and low levels of LH
(3) low levels of oestrogen and LH
(4) high levels of oestrogen and LH
29. Which of the following cannot be seen in the ovarian cortex during proliferation phase?
(1) Corpus luteum
(2) Primary follicle
(3) Secondary follicle
(4) Graafian follicle
30. The blood levels of FSH and LH attain a peak
(1) just after menstruation
(2) just before menstruation
(3) just after ovulation
(4) just before ovulation
31. In a typical 28-day menstrual cycle, luteal phase lasts for about
(1) 14 days (2) 3 days
(3) 9 days (4) 21 days
32. The levels of both oestrogen and progesterone are minimum
(1) during late follicular phase
(2) during mid luteal phase
(3) at the time of ovulation
(4) at the onset of menstruation
33. Given below are two statements.
Statement I : Menstrual cycles cease during pregnancy.
Statement II : Progesterone levels are high during pregnancy.
In light of the above statements, choose the correct answer from the options given below.
(1) Both statement I and statement II are correct.
(2) Both statement I and statement II are incorrect.
(3) Statement I is correct but statement II is incorrect.
(4) Statement I is incorrect but statement II is correct.
34. Which of the following events occurs within the fallopian tube?
(1) Ovulation (2) Fertilisation
(3) Implantation (4) Menstruation
35. Given below are two statements. One is labelled Assertion (A) and the other is labelled Reason (R).
Assertion (A) : Vagina acts as both copulation canal and fertilisation site.
Reason (R) : Both insemination and fusion of gametes occur in the vagina of female.
In light of the above statements, choose the correct answer from the options given below.
(1) Both (A) and (R) are true and (R) is the correct explanation of (A).
(2) Both (A) and (R) are true but (R) is not the correct explanation of (A).
(3) (A) is true but (R) is false.
(4) Both (A) and (R) are false.
36. During fertilisation, the entry of the sperm induces the completion of (1) meiosis II of the secondary oocyte (2) meiosis II of the primary oocyte (3) meiosis I of the primary oocytes (4) meiosis I of the secondary oocyte
37. The glycoprotein layer secreted by the oocyte around itself is termed
(1) zona fasciculata (2) zona glomerulosa (3) zona reticularis (4) zona pellucida
38. Given below are two statements. One is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : The binding of a sperm causes the cell membrane of the oocyte to become depolarised,which blocks the entry of additional sperms.
Reason (R) : The secretions of the acrosome help the sperm enter the cytoplasm of the ovum through the zona pellucida and the plasma membrane.
In light of the above statements, choose the most appropriate answer from the options given below.
(1) Both (A) and (R) are correct and (R) is the correct explanation of (A).
(2) Both (A) and (R) are correct but (R) is not the correct explanation of (A).
(3) (A) is correct but (R) is not correct.
(4) (A) is not correct but (R) is correct.
39. A human zygote would develop into a male baby if
(1) sperm with X chromosome fertilises ovum with X chromosome
(2) sperm with Y chromosome fertilises ovum with X chromosome
(3) sperm with no sex chromosomes fertilises ovum with X chromosome
(4) sperm with Y chromosome fertilises with ovum with no sex chromosomes
40. Given below are two statements.One is labelled Assertion (A) and the other is labelled Reason (R).
Assertion (A) : Chorionic villi are instrumental in the formation of placenta.
Reason (R) : Chorionic villi are fingerlike projections of the trophoblast which interdigitate with the maternal tissue.
In light of the above statements, choose the correct answer from the options given below.
(1) Both (A) and (R) are true and (R) is the correct explanation of (A).
(2) Both (A) and (R) are true but (R) is not the correct explanation of (A).
(3) (A) is true but (R) is false.
(4) Both (A) and (R) are false.
41. A sign ificant amount of progesterone is secreted by the a. corpus luteum
b. testis
c. placenta
(1) a only
(2) b and c only
(3) c only
(4) a and c only
42. After implantation, which of the following differentiates into embryonic ectoderm, endoderm, and mesoderm?
(1) Inner cell mass
(2) Trophoblast
(3) Placenta
(4) Hypoblast
43. Match Column-I with Column-II.
Column-I
Column-II
(A) Foetus develops limbs and digits (I) End of 24 weeks
(B) External genital organs are well developed (II) End of second month
(C) Hair on head (III) End of 12 weeks
(D) Body is covered with fine hair (IV) Fifth month
Select the correct option.
(A) (B) (C) (D)
(1) III II IV I
(2) II III I IV
ANSWER KEY
(3) II III IV I
(4) IV I II III
44. The hormones that stimulate milk secretion and milk ejection ar respectively
(1) oxytocin and prolactin
(2) prolactin and oxytocin
(3) progesterone and oestrogen
(4) prolactin and progesterone
45. Given below are two statements.
Statement I : Parturition is induced by a complex neuroendocrine mechanism involving cortisol, oestrogen and oxytocin.
Statement II : The signals for parturition originate from the fully developed foetus and the placenta which induce foetal ejection reflex.
In light of the above statements, choose the correct answer from the options given below.
(1) Both statement I and statement II are correct.
(2) Both statement I and statement II are incorrect.
(3) Statement I is correct but statement II is incorrect.
(4) Statement I is incorrect but statement II is correct.
Further Exploration
Matching Type
Assertion and Reason
Brain Teasers
Flashback
Chapter Test
REPRODUCTIVE HEALTH CHAPTER 3
Chapter Outline
3.1 Reproductive Health –Problems and Strategies
3.2 Population Stabilisation and Birth Control
3.3 Medical Termination of Pregnancy
3.4 Sexually Transmitted Infections (STIs)
3.5 Infertility
3.1 REPRODUCTIVE HEALTH –PROBLEMS AND STRATEGIES
The term reproductive health refers to healthy reproductive organs with normal functions. It has a broader perspective and includes emotional and social aspects of reproduction. According to the World Health Organisation (WHO) , reproductive health means total well-being in all aspects of reproduction, i.e., physical, emotional, behavioural and social.
India’s Initiatives in Reproductive Health
India was amongst the first countries in the world to initiate action plans and programmes at a national level to attain total reproductive health as a social goal.
India initiated programmes called “family planning” in 1951 and periodically assessed over the past decades.
Improved programmes covering wider reproduction-related areas are currently in operation under the popular name
Reproductive and Child Health Care (RCH) programmes.
Strategies for Achieving Reproductive Health
■ Creating awareness about reproductionrelated aspects through audio-visual and the print-media.
■ Introduction of sex education in schools to provide correct information about reproductive organs, adolescence related changes, safe, and hygienic sexual practices, and sexually transmitted infections (STIs).
■ Educating people, especially fertile couples and those in the marriageable age group, about available birth control options.
■ Care of pregnant mothers, post-natal care of the mother, child and breastfeeding.
■ Providing equal opportunities for the male and female children.
■ Creating awareness of problems due to uncontrolled social evils like sex-abuse and sex-related crimes.
■ Medical assistance and care to people with reproduction-related problems like pregnancy, parturition, STIs, abortions, contraception, menstrual problems, infertility, etc.
■ Banning amniocentesis for the purpose of sex determination to prevent female foeticide.
■ Massive child immunisation.
Indicators of a reproductively healthy society:
■ Better awareness about sex-related matters
■ Increased number of medically assisted deliveries
■ Improved post-natal care leading to decreased maternal and infant mortality rates
■ Rise in the number of couples with small families
■ Enhanced detection and cure of sexually transmitted diseases (STDs)
■ Overall improvement in medical facilities for all sex-related problems
3.2 POPULATION STABILISATION AND BIRTH CONTROL
Understanding population growth and the importance of birth control measures is crucial for reproductive health.
3.2.1 Population Explosion and Control Measures
Increased health facilities, along with better living conditions, had an explosive impact on the growth of the population ( Table 3.1).
Table 3.1 World and Indian population growth
Reasons for the rapid growth of the population
■ Decline in death rate
■ Decline in maternal mortality rate (MMR)
■ Decline in infant mortality rate (IMR)
■ Increase in the number of people in reproducible age
■ Control of diseases
Population growth rate and concerns
We could only marginally bring down the
population growth rate through our RCH programmes. According to the 2011 census report, the population growth rate was less than 2 per cent, i.e., 20/1000/year, a rate at which our population could increase rapidly. Such a rapid growth rate could lead to scarcity of the basic requirements, i.e., food, shelter, etc.
Government measures
■ Encouraging smaller families through the use of various contraceptive methods is the most important step to overcome the problem.
■ Statutory raising of the marriageable age of females to 18 years and that of males to 21 years.
■ Incentives to couples with small families. The slogans “Hum Do Hamare Do” (we two, our two) and “a girl or a boy, a small family is joy” (one-child norm) encourage the idea of limiting family size.
3.2.2 Contraception
C ontracepti ve methods help to prevent unwanted pregnancies. Selection of a suitable contraceptive method and its use should always be undertaken in consultation with qualified medical professionals. Contraceptives are not regular requirements for the maintenance of reproductive health. They are practiced against a natural reproductive event, i.e., conception/ pregnancy. These methods are helpful either to prevent pregnancy or to delay or space pregnancy due to personal reasons.
Features of an Ideal Contraceptive
■ User-friendly
■ Easily available
■ Effective and reversible
■ Minimal or no side-effects
■ Non-interference with the user’s sexual drive, desire, or act
Methods of Contraception
Contraceptive methods are grouped into the following categories:
I. Natural (Traditional) Methods
These methods work on the principle of avoiding chances of ovum and sperm meeting.
Side effects are almost nil in these methods as no medicines or devices are used. The chances of failure of this method are high.
The natural methods of contraception include periodic abstinence, coitus interruputs, and lactational amenorrhoea.
1. Periodic abstinence or rhythm method
Couples avoid or abstain from coitus from day 10 to 17 of the menstrual cycle to prevent conception. As chances of fertilisation are very high during this period, it is called the fertile period.
The safe period refers to the phase when a woman is least likely to conceive. In a typical 28-day menstrual cycle, it extends from day 18 of a cycle to day 9 of the next cycle.
2. Withdrawal method or coitus interruptus
The male partner withdraws his penis from the vagina just before ejaculation to avoid insemination.
3. Lactational amenorrhea
Menstrual cycle and ovulation do not occur during the period of intense lactation following childbirth. Prolactin produced during lactation inhibits the secretion of gonadotropins and stops ovulation.
Lactational amenorrhea has been reported to be effective only up to a maximum period of six months following parturition.
II. Barrier methods
Physically, the meeting of ovum and sperm is prevented with the help of barriers. These are available for both men and women.
1. Condoms
They are made of thin rubber or latex sheath and are used to cover the penis in the male or vagina and cervix in the female before coitus so that ejected semen would not enter the female reproductive tract. Nirodh is a well-known brand of male condoms.
The use of condoms has increased in recent years due to its additional benefit of protecting the user from contracting STIs and AIDS. Both male and female condoms are disposable, can be self inserted and thereby give privacy to the user.
2. Reusable barriers
They include diaphragms, cervical caps and vaults made of rubber. These are inserted into the female reproductive tract to cover the cervix during coitus. They prevent conception by blocking the entry of sperm.
They require proper fitting and insertion to be effective.
3. Spermicidal creams, jellies, and foams
These chemical contraceptives immobilise or kill sperm, preventing fertilisation. They are usually used along with barriers to increase contraceptive efficiency.
Spermicidal creams, jellies and foams contain boric acid, lactic acid, citric acid, zinc sulphate, potassium permanganate, etc.
III. Intra Uterine Devices (IUDs)
IUD is one of the most widely accepted, effective and popular methods of contraception in India. These devices are inserted by doctors
or expert nurses in the uterus through the vagina. IUDs are ideal for females who want to delay pregnancy or space children.
A list of IUDs, their examples and their mode of action is summarised in Table 3.2
Table 3.2 Types of IUDs and their mode of action
1) Nonmedicated IUDs Lippes loop Increase phagocytosis of sperms in the uterus.
2) Copperreleasing IUDs CuT, Cu7, Multiload 375 Release Cu ions, which suppress sperm motility and fertilising capacity
Hormones make the uterus unsuitable for implantation and cervix hostile to sperms, in addition to the effects of (1) and (2).
Progestin in hormone-releasing IUDs, minipills or implants increases the thickness of cervical mucus, creating a barrier that hinders sperm movement from the vagina to the uterus, reducing the likelihood of fertilisation.
IV. Hormonal Methods
They are hormone-containing contraceptives. Hormonal methods are three types:
1. Oral Contraceptives (Pills):
Oral administration of low doses of either progestogens alone or in combination with
oestrogen is a commonly used contraceptive method for females. These are popularly known as “the pills” since they are typically in the form of tablets,
Pills have to be taken daily for a period of 21 days, starting preferably within the first five days of the menstrual cycle. After a gap of 7 days (during which menstruation occurs), it has to be repeated in the same pattern as long as the female desires to prevent conception.
Pills are very effective with fewer side effects, high contraceptive value and are well accepted by females.
Mechanism of Action:
■ Pills inhibit ovulation (because they inhibit the secretion of FSH and LH by the pituitary gland).
■ They prevent implantation.
■ They alter the quality of cervical mucus to prevent or retard the entry of sperm.
Saheli is the new oral non-steroidal contraceptive for females. It is a “ once a week ” pill with very few side effects and high contraceptive value. Saheli is developed by scientists at the Central Drug Research Institute (CDRI), Lucknow.
Saheli contains the drug centchroman (ormeloxifene) , a selective oestrogen receptor modulator (SERM). It obstructs oestrogen receptors in the uterus, preventing endometrial thickening during the proliferative phase. Consequently, when ovulation occurs, the endometrium remains thin, impeding the process of implantation.
2. Injectables and Implants:
Progestogens alone or in combination with oestrogen are used by females as injections or subcutaneous implants (Fig. 3.1). The mode
of action of these injections and implants is similar to that of pills, and their effective periods are much longer.
3. Emergency Contraceptives:
It is treatment for unprotected sex, sexual assault, missed periods and other reasons that have a risk of pregnancy. Administration of progestogens or progestogen-oestrogen combinations or IUDs within 72 hours of coitus have been found to be very effective as emergency contraceptives.
Norplant
3.1 Some commonly used contraceptive devices
V. Surgical methods (Sterilisation)
These are advised as terminal methods to prevent any more pregnancies. These are very effective and block gamete transport, thereby preventing the meeting of gametes (fertilisation). Sterilisation methods are highly effective, but their reversibility is very poor.
The sterilisation procedure in the male is called vasectomy. A small part of the vas deferens is removed or tied up through a small incision on the scrotum.
Vasectomy does not stop spermatogenesis but sperm can not reach the exterior. There
is no effect on sexual desire. A vasectomised man can ejaculate semen that lacks sperm.
The sterilisation procedure in the female is called tubectomy. A small part of the fallopian tube is removed or tied up through a small incision in the abdomen or through the vagina (Fig. 3.2)
Tubectomy does not influence oogenesis, ovulation, menstruation and coitus.
Side Effects of Contraceptive Methods
Contraceptive methods have a significant role in checking the uncontrolled growth of the population. However, there are possible illeffects like:
Fig.
Fig. 3.2 Sterilisation
1. Nausea
2. Abdominal pain
3. Breakthrough bleeding
4. Irregular menstrual bleeding
5. Breast cancer, though not very significant.
Checkpoint
Q. Does a vasectomised man ejeculate semen during coitus?
Yes, but the semen does not contain sperm.
Answer:
TEST YOURSELF
1. ‘Saheli’ is an oral contraceptive developed by scientists of (1) ICMR (2) CDRI
(3) CCMB (4) CDC
2. Intrauterine devices do not
(1) cause phagocytosis of sperm
(2) block the entry of sperm into the vagina
(3) prevent conception
(4) suppress sperm motility
3. Spermicidal creams, jellies and foams are usually used along with to increase their contraceptive efficiency.
(1) implants
(2) barriers
(3) injections
(4) IUDs
4. Which ions released by the IUDs are toxic to the sperm?
(1) Iron
(2) Cobalt
(3) Copper
(4) Magnesium
5. Which of the following are the common methods of emergency contraception?
(1) Condoms and pills
(2) Vasectomy and tubectomy
(3) Spermicidal creams and jellies
(4) Pills and IUDs
6. Besides contraception, an additional benefit of condoms is that
(1) they increase the sexual urge
(2) they are reusable
(3) they are terminal methods
(4) they protect the user from STIs
7. Which of the following is not a natural method of contraception?
(1) Periodic abstinence
(2) Emergency contraception
(3) Coitus interruptus
(4) Lactational amenorrhoea
8. Which of the following do not block sperm from reaching and fertilising an egg by forming a physical barrier?
(1) Vaults
(2) Copper-releasing IUDs
(3) Diaphragms
(4) Cervical caps
9. The terminal methods of birth control are (1) injections and implants
(2) vasectomy and tubectomy
(3) intrauterine devices
(4) male and female condoms
10. The natural method of contraception in which the male partner withdraws his penis from the vagina just before ejaculation is termed
(1) periodic abstinence
(2) emergency contraception
(3) coitus interruptus
(4) lactational amenorrhoea
Answer Key
(1) 2 (2) 2 (3) 2 (4) 3
(5) 4 (6) 4 (7) 2 (8) 2
(9) 2 (10) 3
3.3 MEDICAL TERMINATION OF PREGNANCY (MTP)
Intentional or voluntary termination of pregnancy is called Medical Termination of Pregnancy (MTP) or induced abortion. Nearly 45 to 50 million MTPs are performed in a year all over the world, which accounts for 1/5th of the total number of conceived pregnancies in a year.
Purpose of MTP
■ To get rid of unwanted pregnancies that occur due to:
■ casual unprotected intercourse
■ failure of the contraceptive used during coitus
■ rapes
■ Cases where continuation of the pregnancy could be harmful or even fatal to the mother or foetus or both.
MTPs are considered relatively safe during the first trimester, i.e., up to 12 weeks of pregnancy. Second trimester abortions are much more riskier. MTPs performed illegally by unqualified quacks are not only unsafe but could be fatal too.
Second-trimester (and third-trimester) abortions are riskier because the foetus is more developed, the placenta is firmly attached, and the procedure becomes more invasive, increasing the chances of excessive bleeding, uterine perforation, infection, and complications affecting future pregnancies.
Misuse of MTP
Sometimes, the sex of the unborn child is determined by amniocentesis, and if the foetus is found to be female, it is terminated by MTP (female foeticide). Effective counselling on the need to avoid unprotected coitus and the
risk factors involved in illegal abortions, as well as providing more health care facilities, could reverse the misuse of MTP.
Legality of MTP
The acceptance and legalisation of MTP remain a topic of debate in many countries due to the emotional, ethical, religious, and social concerns associated with it.
MTP Act
Govt. of India legalised MTP in 1971, with some strict conditions to avoid its misuse. Such restrictions are all the more important to check indiscriminate and illegal female foeticides, which are reported to be high in India.
MTP Amendment Act
The Medical Termination of Pregnancy (Amendment) Act, 2017, was enacted by the government of India with the intention of reducing the incidence of illegal abortions and consequent maternal mortality and morbidity (illness or disease). According to this Act, a pregnancy may be terminated on certain considered grounds on the opinion of the:
(1) one registered medical practitioner within the first 12 weeks of pregnancy.
(2) two registered medical practitioners during 13-24 weeks.
The accepted grounds for such termination of pregnancies are:
(1) The continuation of the pregnancy would involve a risk to the life of the pregnant woman or of grave injury to physical or mental health or
(2) There is a substantial risk that if the child were born, it would suffer from such physical or mental abnormalities as to be seriously handicapped.
Amniocentesis
It helps in screening for abnormalities in the developing foetus. Amniotic fluid is sampled
3: Reproductive Health
using a hollow needle inserted into the uterus, collecting foetal skin cells and a number of proteins, especially enzymes. The cells can be cultured in vitro for further examination (Fig. 3.3)
Uses of Amniocentesis:
■ Sex determination by the presence or absence of Barr bodies in foetal cells.
■ Detection of metabolic disorders like phenylketonuria, alkaptonuria, etc., by enzyme analysis.
■ Detection of chromosomal disorders like Down’s syndrome.
■ Detection of Mendelian disorders like haemophilia, sickle cell anaemia etc., determine the survivability of foetus.
TEST YOURSELF
1. Government of India legalised MTP in the year (1) 1951 (2) 1961 (3) 1971 (4) 1981
2. MTPs are very risky during (1) first month of pregnancy. (2) second month of pregnancy. (3) third month of pregnancy. (4) second trimester of pregnancy.
3. In the context of reproductive health, MTP is also known as (1) test tube baby
(2) ectopic pregnancy
(3) artificial insemination
(4) induced abortion
Answer Key
(1) 3 (2) 4 (3) 4
3.4 SEXUALLY TRANSMITTED INFECTIONS (
STIs )
Diseases or infections that are transmitted through sexual intercourse are called sexually transmitted infections (STIs), venereal diseases (VD) or reproductive tract infections (RTIs). They were formerly also called STDs (sexually transmitted diseases). STIs are a major threat to a healthy society. Common STIs include bacterial, viral and protozoan diseases. HIV infection is the most dangerous STI. A list of some STIs and the causative agents is summarised in Table 3.3.
4. Genital warts, Cervical cancer Human Papilloma Virus (HPV)
5. Trichomoniasis Trichomonas vaginalis (a protozoan parasite)
6. Chlamydiasis Chlamydia trachomatis (bacteria)
7. Hepatitis-B HBV
8. HIV infection/ AIDS HIV (Human immunodeficiency virus)
Fig. 3.3 Amniocentesis
HIV and hepatitis B are sexually transmitted infections that do not specifically affect sex organs.
Methods of transmission of STIs
■ Sexual intercourse
■ Sharing injection needles, surgical instruments, etc., with infected persons (e.g., hepatitis-B and HIV)
■ Transfusion of contaminated blood
■ From the infected mother to the foetus.
Early Symptoms of STIs
■ Itching
■ Fluid discharge
■ Slight pain, swellings, etc., in the genital region.
Infected females may often be asymptomatic and, hence, may remain undetected for long.
Complications of STIs
■ Pelvic inflammatory disease (PID)
■ Abortions
■ Stillbirths
■ Ectopic pregnancies
■ Infertility
■ Cancer of the reproductive tract
Stillbirth is the birth of a baby who has died in the womb. An ectopic pregnancy occurs when a fertilised egg implants outside the uterus, most commonly in the fallopian tube. The foetus generally cannot survive.
Treatment
Except for Hepatitis–B, Genital herpes and HIV infection, STIs are completely curable if they are detected early and treated properly.
Persons in the age group of 15-24 years are more vulnerable to contracting STIs. The patient should seek complete treatment if diagnosed with STI.
Preventive measures
■ Avoid sex with unknown partners/multiple partners.
■ Always use condoms during intercourse.
■ Consulting the qualified doctor for early detection in case of doubt
Prevention or early detection and cure of these diseases are given prime consideration under the reproductive healthcare programmes.
TEST YOURSELF
1. Which of the following STIs is completely curable?
(1) HIV
(2) Hepatitis-B
(3) Genital Herpes
(4) Chalmydiasis
2. Which one of the following diseases is not sexually transmitted?
(1) Filariasis
(2) Syphilis
(3) Gonorrhoea
(4) Trichomoniasis
Answer Key
(1) 4 (2) 1
3.5 INFERTILITY
Infertility is the inability to produce children despite two years of unprotected sexual cohabitation. The reasons for this could be many: physical, congenital, diseases, drugs, immunological or even psychological.
Specialised healthcare units, such as infertility clinics, could help in diagnosis and corrective treatment of some of these disorders
and enable these couples to have children. If the corrective treatment is not possible, the couples could be assisted to have children through certain special techniques commonly known as assisted reproductive technologies (ARTs).
3.5.1 Assisted Reproductive Technologies (ARTs)
Assisted Reproductive Technologies (ARTs) refer to medical procedures designed to aid infertile individuals or couples in achieving pregnancy. They include IVF (Test-tube baby), IVF-ET, ZIFT, GIFT, ICSI and Artificial Insemination (AI).
In vitro Fertilisation-Embryo Transfer
In vitro fertilisation (IVF) is the process of fertilisation outside the body, under conditions closely resembling those within the body.IVF followed by embryo transfer (ET) is a popular
method of assisted reproductive technology commonly known as the test tube baby program (Fig. 3.4).
IVF-ET involves the collection of eggs from the wife or a donor (female) and sperm from the husband or a donor (male). These collected gametes are then induced to form a zygote under simulated conditions within a laboratory setting.
The resulting zygote or early embryos can be transferred into the female reproductive tract for the completion of further embryonic development by two methods:
(a) Zygote intrafallopian transfer (ZIFT) involves placing the zygote or early embryos (with up to eight blastomeres) into the fallopian tube.
(b) Intrauterine transfer (IUT) is the transfer of embryos with more than eight blastomeres into the uterus.
Fig. 3.4 In vitro fertilisation-embryo transfer
The baby produced by conceiving in a culture medium and nourishing in the uterus is called a test tube baby.
Embryos formed by in vivo fertilisation (fusion of gametes within the female) could also be used for such transfer to assist those females who cannot conceive.
GIFT (Gamete Intra Fallopian Transfer)
It is the transfer of ovum collected from a donor into the fallopian tube of another female who cannot produce ovum but can provide a suitable environment for fertilisation (in vivo) and further development.
ICSI (Intra Cytoplasmic Sperm Injection)
It is a procedure to form an embryo in the laboratory in which a sperm is directly injected into the ovum by micropuncture of zona pellucida.
Artificial Insemination (AI)
Infertility cases either due to the inability of the male partner to inseminate the female or due to very low sperm counts in the ejaculates, could be corrected by artificial insemination (AI) technique. In this technique, the semen collected either from the husband or a healthy donor is artificially introduced into the female reproductive tract (e.g., vagina or uterus) for in vivo fertilisation. Intrauterine insemination (IUI) is the introduction of semen into the uterus. Intravaginal insemination (IVI) is the introduction of semen into the vagina.
The availability of ARTs is limited to a few cities in the country due to the requirement of specialised professionals and expensive
instrumentation. Emotional, religious, and social factors also deter the use of ARTs. Considering many orphaned children in India, legal adoption is one of the best methods for couples seeking parenthood.
Checkpoint
1. Giv e one fundamental similarity and one difference between GIFT and ZIFT.
2. How is it possible for three parents to be involved in the birth of a child through the IVF-ET technique?
2. The ovum of the wife/donor (biological mother) and sperm of the husband/donor (biological father) can be induced to form a zygote in vitro. The embryo can be implanted in the uterus of another woman (surrogate mother).
GIFT involves transferring eggs into the fallopian tube, allowing fertilisation to occur within the woman’s body. In contrast, ZIFT involves transferring the fertilised egg (zygote) directly into the fallopian tube after in vitro rtilisation.fe
1. Both GIFT and ZIFT involve the placement of reproductive materials (gametes and zygotes) directly into the fallopian tube.
Answers:
TEST YOURSELF
1. ZIFT involves the transfer of
(1) only zygote into the fallopian tube
(2) only embryos with more than 8 blastomeres into the uterus
(3) zygote or embryo with up to 8 blastomeres into the fallopian tube
(4) zygote or embryo with up to 8 blastomeres into the uterus
2. Which of the following assisted reproductive technologies involves the transfer of the ovum into the fallopian tube?
(1) ZIFT
(2) ICSI
(3) GIFT
(4) IVF
(3) Which of the following is not a method of ART in humans?
(1) MTP
(2) IUT
(3) GIFT
(4) ZIFT
4. In the context of assisted reproductive technologies (ART), IUT refers to the transfer of
(1) zygote into the fallopian tube
(2) zygote or embryos with upto 8 blastomeres into the fallopian tube
CHAPTER REVIEW
Reproductive Health - Problems and Strategies
■ According to the World Health Organisation (WHO), reproductive health means total well-being in all aspects of reproduction, i.e., physical, emotional, behavioural and social.
■ India was amongst the first countries in the world to initiate action plans and programmes (family planning) at a national level to attain total reproductive health as a social goal.
■ The ‘family planning’ programmes in India were initiated in 1951.
■ Improved programmes covering wider reproduction-related areas are currently
(3) embryos with more than 8 blastomeres into the uterus
(4) zygote or embryos with upto 8 blastomeres into the uterus
5. Which of the following assists in conception?
(1) IUD
(2) MTP
(3) STI
(4) IUI
6. GIFT is an assisted reproductive technology indicated for a woman
(1) whose uterus does not support implantation
(2) who cannot provide a suitable environment for fertilisation
(3) who cannot produce an ovum
(4) who wants to get rid of unwanted pregnancy
Answer Key
(1) 3 (2) 3 (3) 1 (4) 3
(5) 4 (6) 3
in operation under the popular name ‘Reproductive and Child Health Care (RCH) programmes’.
■ A statutory ban is imposed on amniocentesis for sex-determination to legally check the increasing female foeticides.
■ Saheli is a new oral contraceptive for females developed by the Central Drug Research Institute (CDRI) in Lucknow.
■ Saheli is a non-steroidal preparation with less side effects and doesn’t affect ovulation.
Population Stabilisation and Birth Control
■ According to the 2011 census report, the population growth rate was less than 2 per cent, around 1.7 per cent, i.e., 20/1000/year.
■ To tackle the population growth in India, a statutory raising of the marriageable age of females to 18 years and that of males to 21 years was implemented.
■ Periodic abstinence, coitus interruptus and lactational amenorrhea are natural contraceptive methods.
■ Extensive breastfeeding may interrupt the menstrual cycle up to a maximum period of 6 months following parturition.
■ As no medicines or devices are used in natural methods, side effects are almost nil.
■ In barrier methods, the ovum and sperm are prevented from physically meeting.
■ Condoms are barriers for both males and females.
■ Condoms are thin rubber or latex sheaths that cover the penis or vagina and cervix.
■ Nirodh is a male condom.
■ Condoms are disposable and protect against STIs.
■ Diaphragms, cervical caps and vaults are also barriers made of rubber that are inserted into the female reproductive tract to cover the cervix during coitus.
■ If spermicidal creams, jellies and foams are used along with the barriers, it may increase their contraceptive efficiency.
■ IUDs are ideal contraceptives for females who want to delay pregnancy and/or space children.
■ IUDs (e.g., Lippes loop) increase phagocytosis of sperms within the uterus.
■ CuT, Cu7 and Multiload 375 release Cu ions that suppress sperm motility and the fertilising capacity of sperm.
■ Ho rmone-releasing IUDs (e.g., progestasert, LNG 20) make the uterus unsuitable for implantation and the cervix hostile to the sperms.
■ Oral contraceptive pills inhibit ovulation and implantation as well as alter the quality of cervical mucus to prevent/ retard entry of sperms.
■ Administration of progestogens or progestogen-oestrogen combinations or IUDs within 72 hours of coitus have been found to be very effective as emergency contraceptives.
■ Surgical methods (vasectomy and tubectomy) prevent conception by blocking gamete transport.
■ Sterilisation methods are highly effective and poorly reversible.
Medical Termination of Pregnancy
■ The government of India legalised MTP in 1971 with some strict conditions to avoid its misuse.
■ MTP (Amendment) Act, 2017, was enacted with the intention of reducing the incidence of illegal abortions.
■ If the pregnancy has lasted more than 12 weeks but fewer than 24 weeks, two registered medical practitioners must give their opinion to allow MTP.
■ MTPs are considered relatively safe during the first trimester. Second-trimester abortions are much more riskier.
■ Amniocentesis is a foetal sex determination test based on the chromosomal pattern in the amniotic fluid surrounding the developing embryo.
Sexually Transmitted Infections
STD Caused by
Gonorrhea Nisseria gonorrheae (bacterium)
Syphilis Treponema pallidum (bacterium)
Chlamydiasis Chlamydia trachomatis (bacterium)
Genital herpes Herpes simplex virus
Genital warts Human papilloma virus
Hepatitis-B Hepatitis-B virus
AIDS Human immunodeficiency virus
Trichomoniasis Trichomonas vaginalis (protozoan)
■ Complications of STIs include pelvic inflammatory diseases (PID), abortions, still births, ectopic pregnancies, infertility or cancer of the reproductive tract.
Infertility
■ Infertility is the inability to conceive or produce children even after two years of unprotected sexual cohabitation.
■ In vitro fertilisation followed by embryo transfer (ET) is popularly known as the test tube baby programme.
■ ARTs involving in vitro fertilisation are Test tube baby procedure, ZIFT, ICSI.
■ ARTs which involve in vivo fertilisation are AI, IUI, GIFT.
■ The inability of the male partner to inseminate the female or due to very low sperm counts in the ejaculates could be corrected by artificial insemination (AI) technique.
Exercises
NEET DRILL
Reproductive Health - Problems and Strategies
1. The family planning program in India was introduced in the year
(1) 1941 (2) 1951
(3) 1961 (4) 1971
2. The Prenatal Diagnostics Act prohibits the use of amniocentesis for the detection of (1) chromosomal disorders
(2) sex of the foetus
(3) metabolic disorders
(4) congenital malformations
3. Amniocentesis is a medical procedure used to
(1) check for genetic disorders in the developing foetus
(2) drain off excess amniotic fluid around the foetus
(3) induce abortion when continuation of pregnancy could harm the foetus/mother (4) introduce semen into the vagina or uterus of a woman
Population Stabilisation and Birth Control
4. Which of the following is a hormonereleasing IUD?
(1) Norplant (2) Lippes loop
(3) Femidom (4) Progestasert
5. Which of the following contraceptives are similar in their mode of action?
(1) Saheli and Nirodh
(2) IUD and tubectomy
(3) Vasectomy and Nirodh
(4) Implants and injectables
6. Select the incorrect statement about contraceptive implants.
(1) They are implanted under the skin.
(2) Their mode of action is similar to that of pills.
(3) Their effective periods are much shorter.
(4) They release progestogens.
7. Population explosion occurs when
(1) infant mortality rate and maternal mortality rate decrease
(2) infant mortality rate and maternal mortality rate increase
(3) infant mortality rate increases and maternal mortality rate decreases
(4) fertility rates and agricultural production decrease
8. Which of the following statements is incorrect about Nirodh?
(1) It protects the user from contracting AIDS.
(2) It is popular brand of female condom.
(3) It is used just before coitus so that ejaculated semen would not enter female reproductive tract.
(4) It is made of thin rubber sheath.
9. Oral contraceptive pills do not
(1) inhibit ovulation
(2) thicken cervical mucus
(3) prevent implantation
(4) increase phagocytosis of sperm
10. Which of the following is not correct about IUDs?
(1) They suppress motility and fertilising capacity of sperms.
(2) Some of them release hormones that prevent implantation.
(3) Besides preventing pregnancy, they protect against STIs.
(4) They are T-shaped devices inserted by doctors or nurses into the uterus.
11. Which of the following contraceptive devices also protect the users against sexually transmitted diseases?
(1) Condom
(2) Multiload 375
(3) IUD
(4) Copper-T
12. Emergency contraceptives are effective if used within
(1) 72 hours from the time of ovulation
(2) three days from the time of coitus
(3) one week from the time of ovulation
(4) one week from the time of coitus
13. ‘Saheli’ is an oral contraceptive which works primarily by preventing
(1) ovulation
(2) implantation
(3) fertilisation
(4) oogenesis
14. Which of the following are often used to increase the efficacy of condoms and diaphragms?
(1) Oral pills
(2) Spermicides
(3) Implants
(4) Injections
15. Which of the following contraceptive methods does not require male partner’s cooperation?
(1) Coitus interruptus
(2) Periodic abstinence
(3) Vasectomy
(4) Oral pills
16. Select the correct match.
(1) Barrier methods - Diaphragms, cervical caps and vaults
(2) Hormone-releasing IUDs - Progestasert, LNG-20 and Multiload 375
(3) Assisted reproductive technologies - IVF, IUI and MTP
(4) Sterilisation - Vasectomy, tubectomy and amniocentesis
17. Which of the following statements is not true with respect to tubectomy?
(1) It is more difficult than vasectomy and is even more difficult to reverse.
(2) No ovulation occurs after the tubectomy, hence no fertilisation.
(3) It involves ligation of both fallopian tubes.
(4) The failure rate of this method is almost zero.
18. Which of the following will fail to check the problem of the population explosion?
(1) Acquiring one child norm
(2) Decreasing the marriageable age
(3) Use of contraceptive methods
(4) Providing education to the people
19. Which of the following contraceptives are available for both men and women?
(1) Condoms
(2) Diaphragms
(3) IUDs
(4) Morning-after pills
20. Which of the following prevents conception by preventing the physical meeting of sperm and ovum?
(1) Norplant
(2) Lippe’s loop
(3) Saheli
(4) Nirodh
21. A woman fully breastfeeding her child and does not want to conceive should definitely use contraceptives
(1) from 7 month after parturition
(2) only after one year following parturition
(3) right from the day of parturition
(4) from 2 week after parturition
Medical Termination of Pregnancy
22. Which of the following is not a legal ground for MTP in India?
(1) The continuation of the pregnancy would involve a risk to the life of the pregnant woman
(2) The risk of child to be born suffering from serious physical or mental abnormalities
(3) The continuation of the pregnancy would involve a risk to physical or mental health of the pregnant woman
(4) The foetus is found to be female in amniocentesis and the couple wants only male child.
23. Select the correct statement from the following.
(1) The Pre-natal Diagnostic Techniques Act permits the use of amniocentesis for sex determination.
(2) The legal age of marriage in India is 18 years for males and 21 years for females.
(3) Family planning programme was initiated in India in the year 1961.
(4) Government of India legalised MTP in 1971 with some strict conditions to avoid its misuse.
Sexually Transmitted Infections (STIs)
24. Select the incorrect statement from the following.
(1) Other than sexual intercourse, STIs can be transmitted through infected medical devices, blood transfusion or from mother to foetus.
(2) Females infected with STIs may often be asymptomatic and hence, infections remain undetected for long.
(3) Failure of timely detection and treatment may lead to ectopic pregnancies, pelvic inflammatory diseases and infertility.
(4) Except HIV, all STIs are completely curable with proper treatment.
25. The incurable sexually transmitted infections are caused by
(1) bacteria
(2) protozoans
(3) viruses
(4) fungi
26. Select the set of STIs.
(1) AIDs and chickenpox
(2) Chikungunya and dengue
(3) Malaria and syphilis
(4) Genital warts and Hepatitis-B
27. Which of the following STIs does not affect the sex organs in particular?
(1) Syphilis
(2) AIDS
(3) Gonorrhoea
(4) Genital warts
Infertility
28. Select the correct set of assisted reproductive technologies (ARTs).
(1) IUI, IUT, IUD
(2) AI, ET, MTP
(3) IVF, STI, AI
(4) ZIFT, GIFT, ICSI
29. The injection of a single spermatozoon directly into the cytoplasm of an oocyte is termed
(1) ICSI (2) ZIFT
(3) MTP (4) GIFT
30. Which of the following is an ART suitable for a woman who cannot produce an ovum but has functional fallopian tubes and uterus?
(1) Tubectomy (2) MTP
(3) IUI (4) GIFT
31. Test tube baby treatment involves the placement of zygote into the (1) ovary (2) vagina
(3) uterus (4) fallopian tube
32. Select the incorrect pair regarding assisted reproductive technologies (ARTs).
(1) IVF – Fertilisation outside the body in almost similar conditions as that in the body
(2) ICSI – Direct injection of a single spermatozoon into the cytoplasm of an oocyte
(3) GIFT – Transfer of zygote or early embryo to the fallopian tube
(4) IUI – Introduction of husband’s or donor’s semen into the womb
33. Which of the following is introduced into the uterus after in vitro fertilisation (IVF)?
(1) Foetus (2) Zygote
(3) Embryo (4) Ovum
34. Which of the following procedures is not involved in test tube baby programme?
(1) ZIFT (2) IUT
(3) IVF (4) IUD
35. ARTs include
(1) social awareness programmes to educate
FURTHER EXPLORATION
1. Though discontinued due to its side effects, Gossypol derived from cotton plant had been tried as a
(1) female contraceptive
(2) male contraceptive
(3) emergency contraceptive
(4) abortion pill
2. Centchroman is an active ingredient of (1) minipill
(2) Mala-D
(3) Saheli
(4) Morning-after pill
3. Which of the following is not used in birth control pills?
(1) Nonoxynol (2) Oestrogen
(3) Progestogen (4) Ormeloxifene
people about reproductive health and diseases.
(2) research organisation working to produce new and more effective contraceptives for birth control.
(3) a number of special techniques which assist infertile couples to have children.
(4) different techniques to reduce the STIs.
36. Read the following statements.
i) ICSI can solve the fertility problem of a man with low sperm count or low sperm motility.
ii) All sexually transmitted infections affect only sex organs.
iii) MTPs are relatively safe up to 12 weeks of pregnancy.
iv) There is no contraceptive method to prevent pregnancy after coitus.
Which two statements of the above are correct?
(1) (i) and (ii) (2) (iii) and (iv)
(3) (i) and (iii) (4) (ii) and (iv)
4. Which of the following contraceptives contain hormones?
(1) Pills, implants, vaults
(2) Vaginal rings, saheli, diaphragms
(3) Skin patches, vaginal rings, implants
(4) Pills, Lippes loop, implants
5. Only hormone in minipill is (1) oestrogen
(2) progestin
(3) oxytocin
(4) relaxin
6. Chancroid is caused by (1) Nisseria gonorrhoeae
(2) Trepanema pallidum
(3) Haemophilus ducreyi
(4) Human palilloma virus
7. World population day is observed on (1) 11 July (2) 1 December
(3) 21 June (4) 14 November
8. Which of the following is administered to a pregnant woman to induce labour?
(1) Pitocin (2) Mifepristone
(3) Gossypol (4) Ormeloxifene
9. Mala – D and Mala - N are (1) IUDs
(2) progestin-only contraceptive pills
(3) combined oral contraceptive pills
(4) implants
10. Mifepristone (RU 486) is also known as abortion pill as it is antagonistic to which of the following hormones?
(1) Progesterone (2) Oxytocin
(3) Prolactin (4) Prostaglandin
11. Which of the following causes syphilis?
(1) Chlamydia trachomatis
(2) Neisseria gonorrhoeae
MATCHING TYPE QUESTIONS
1. Match Column-I with Column-II.
Column-I Column-II
(A) Withdrawal (I) Prenatal diagnostic test
(B) Diaphragms (II) Nonsteroidal compound
(C) Centchroman (III) Natural method of contraception
(D) Amniocentesis (IV) Barrier method of contraception
Select the correct option.
(A) (B) (C) (D)
(1) III IV II I
(2) IV III II I
(3) II III IV I
(4) III II IV II
(3) Treponema pallidum
(4) Wuchereria bancrofti
12. Ectopic pregnancy refers to (1) implantation of the embryo outside the uterus
(2) pregnancy in the uterus but without implantation of the foetus
(3) pregnancy following in vitro fertilisation and embryo transfer
(4) pregnancy that has extended beyond 42 weeks from the first day of the last menstrual period
13. Select the correct option that describes the hormonal mechanism of lactational amenorrhoea.
(1) Low levels of prolactin stimulate the secretion of GnrH.
(2) Low levels of prolactin inhibit the secretion of GnrH.
(3) High levels of prolactin stimulate the secretion of GnrH.
(4) High levels of prolactin inhibit the secretion of GnrH.
2. Match Column-I with Column-II.
Column-I Column-II
(A) Nirodh (I) Vaginal contraceptive sponge
(B) Today (II) Male condom
(C) Saheli (III) Nonsteroidal pill
(D) Progestasert (IV) Intrauterine device
Select the correct option.
(A) (B) (C) (D)
(1) I II III IV
(2) I II IV III
(3) IV II I III
(4) II I III IV
3. Match Column-I with Column-II.
Column-I Column-II
(A) Multiload 375 (I) Non-medicated IUD
(B) Nirodh (II) Hormone releasing IUD
(C) Lippe’s loop (III) Male condom
(D) Progestasert (IV) Copper releasing IUD
Select the correct option.
(A) (B) (C) (D)
(1) III II I IV
(2) III IV I II
(3) IV III I II
(4) IV III II I
4. Match Column-I with Column-II.
Column-I Column-II
(A) Genital warts (I) Amniocentesis
(B) Ectopic pregnancy (II) Complication of STI
(C) Down’s syndrome (III) HPV
(D) Genital herpes (IV) Not curable
STATEMENT TYPE QUESTIONS
Each question has two statements: statement I (S-I) and statement II (S-II). Mark the correct answer as
(1) if both statement I and statement II are correct,
(2) if both statement I and statement II are incorrect,
(3) if statement I is correct but statement II is incorrect,
(4) if statement I is incorrect but statement II is correct.
1. S-I : Infertility cases due to low sperm counts in the ejaculates, could be corrected by artificial insemination (AI) technique.
Select the correct option.
(A) (B) (C) (D)
(1) IV I II III
(2) IV III II I
(3) I II III IV
(4) III II I IV
5. Match Column-I with Column-II.
Column-I Column-II
(A) Embryo transfer (I) IUI
(B) Artificial insemination (II) IUT
(C) In vitro fertilisation (III) GIFT
(D) Ovum transfer (IV) ICSI
Select the correct option.
(A) (B) (C) (D)
(1) II I III IV
(2) II I IV III
(3) I II III IV
(4) IV III II I
S-II : Artificial insemination involves the direct injection of a sperm into the ovum.
2. S-I : Oral contraceptive pills inhibit ovulation and implantation.
S-II : Oral contraceptive pills cause thinning of cervical mucus.
3. S-I : Following in vitro fertilisation, embryos with more than eight blastomeres are transferred into the fallopian tube to complete their further development.
S-II : Embryos formed by in vivo fertilisation also could be used for embryo transfer to assist t hose females who cannot conceive.
4. S-I : Insertion of IUD within 72 hours of coitus prevents conception.
S-II : IUDs prevent entry of sperm into the female reproductive tract.
5. S-I : Menstrual cycles do not occur during the period of intense lactation.
S-II : Ovulation does not occur in lactating mothers.
6. S-I : Nearly 45-50 million MTPs are performed in a year all over the world.
S-II : MTPs are generally performed to decrease the population.
7. S-I : Persons of the age group 15-24 years are vulnerable to STIs.
S-II : In both men and women, gametogenesis begins at the age group of 15-24 years.
ASSERTION AND REASON QUESTIONS
In each of the following questions, a statement of Assertion (A) is given, followed by a corresponding statement of Reason (R). Mark the correct answer as
(1) if both (A) and (R) are true and (R) is the correct explanation of (A),
(2) if both (A) and (R) are true but (R) is not the correct explanation of (A),
(3) if (A) is true but (R) is false,
(4) if both (A) and (R) are false.
1. (A) : MTPs are considered relatively safe during the first trimester.
(R) : By the end of the first trimester, most of the major organ systems are formed.
2. (A) : Menstrual cycle stops during pregnancy and intense lactation after child birth.
(R) : High levels of oestrogen and progesterone during pregnancy and intense lactation inhibit gonadotropin secretion.
3. (A) : Vasectomy and tubectomy are generally advised as a terminal method of contraception.
8. S-I : Amniocentesis is sometimes misused to identify the sex of foetus.
S-II : Amniocentesis helps to detect certain genetic disorders.
9. S-I : Early symptoms of most STIs are minor and include itching, fluid discharge, slight pain, swellings, etc., in the genital region.
S-II : Infected females may often be asymptomatic and hence, may remain undetected for long.
10. S-I : Prolonged and sustained breastfeeding offers a natural contraception due to the temporary absence of menstrual cycles.
S-II : Lactational amenorrhoea is effective up to two years following parturition.
(R) : The reversibility of these methods is very poor.
4. (A) : All sexually transmitted infections (STIs) are completely curable.
(R) : All STIs cause only minor symptoms like itching, rashes, etc., around the genital area.
5. (A) : Periodic abstinence is a natural contraceptive method in which couples engage in coitus from day 10 to day 17 of a typical 28-day menstrual cycle.
(R) : Day 10 to day 17 of the menstrual cycle is considered the ‘safe period’ during the menstrual cycle.
6. (A) : IUDs are one of the most widely accepted methods of contraception in India.
(R) : IUDs can be effective as contraceptives when used within 72 hours of coitus.
7. (A) : Hepatitis B and HIV infections are not completely curable.
(R) : HIV and HBV can be transmitted by sharing of injection needles and surgical instruments with infected persons.
8. (A) : The use of condoms has increased in recent years.
(R) : Condoms are available for both men and women.
9. (A) : In natural methods of contraception, side effects are almost nil.
(R) : The chances of failure are high in natural methods of contraception.
10. (A) : LNG-20 is a contraceptive device.
(R) : Copper ions suppress sperm motility and the fertilising capacity of the sperm.
11. (A) : Oral contraceptive pills are very popular among the rural women.
BRAIN TEASERS
1. If a woman showing regular 28-day menstrual cycle ovulates on 12th of September, which of the following would be the next ‘safe period’ with regards to rhythm method of contraception?
(1) 8th September to 15th September
(2) 20th September to 10th October
(3) 16th September to 6th October
(4) 6th October to 13th October
2. Which natural steps are bypassed when sperm is directly introduced into the ovum?
(1) Insemination and implantation
(2) Gametogenesis and gestation
(3) Insemination and capacitation
(4) Acrosomal reaction and gestation
3. Sita and Gita are healthy women in their middle ages experiencing regular reproductive cycles. Assume that for no specific reason, Sita undergoes a hysterectomy (surgical removal of the uterus), and Gita undergoes bilateral
(R) : Mode of action of oral pills is similar to that of IUDs and their effective periods are much longer.
12. (A) : IUDs can make the uterus unsuitable for implantation.
(R) : IUDs increase phagocytosis of sperm.
13. (A) : In AI technique, fertilisation occurs internally in the oviduct of female.
(R) : In AI technique, the semen is introduced into the vagina or the uterus of female.
14. (A) : Saheli is a nonsteroidal oral contraceptive for females.
(R) : It is a ‘once a week’ pill with very few side effects.
15. (A) : Women infected by STIs may remain undetected for long.
(R) : Women infected by STIs can often be asymptomatic.
ovariectomy (surgical removal of both ovaries). Select the correct option regarding their reproductive physiology after the surgery.
Sita Gita
Ovulation Menstruation Ovulation Menstruation
(1) Occurs Ceases Ceases Occurs
(2) Occurs Ceases Ceases Ceases
(3) Ceases Occurs Occurs Ceases
(4) Ceases Ceases Ceases Ceases
4. Removal of gonads cannot be considered as a contraceptive option because
(1) it is less effective in preventing pregnancy
(2) it leads to permanent sterility and unavaialble of certain hormones
(3) it can only prevent gamete transport but not gamete production
(4) it is not possible to remove gonads surgically
FLASHBACK (Previous NEET Questions)
1. Following is the list of STDs. Select the diseases which are not completely curable. (2024–R)
A) Genital warts
B) Genital herpes
C) Syphilis
D) Hepatitis-B
E) Trichomoniasis
Choose the correct answer form the options given below.
(1) A and D only
(2) B and D only
(3) A and C only
(4) D and E only
2. Given below are two statements. (2023-M)
Statement I : Intra Cytoplasmic Sperm Injection (ICSI) is a specialised procedure of in vivo fertilisation.
Statement II : Infertility cases due to inability of the male partner to inseminate female can be corrected by artificial insemination (AI).
In light of the above statements, choose the correct answer from the options given below.
(1) Statement I is correct but statement II is incorrect.
(2) Statement I is incorrect but statement II is correct.
(3) Both statement I and statement II are correct.
(4) Both statement I and statement II are incorrect.
3. Match Column-I with Column-II. (2022)
Column-I Column-II
(A) Diaphragms (I) Inhibit ovulation and implantation
(B) Contraceptive pills (II) Increase phagocytosis of sperm within uterus
(C) Intra Uterine Devices (III) Absence of menstrual cycle and ovulation following parturition
(D) Lactational amenorrhea (IV) They cover the cervix blocking the entry of sperms
Select the correct option.
(A) (B) (C) (D)
(1) IV I II III
(2) II IV I III
(3) III II I IV
(4) IV I III II
4. Match Column-I with Column-II. (2021)
Column-I Column-II
(A) Vaults (I) Entry of sperm through cervix is blocked
(B) IUDs (II) Removal of vas deferens
(C) Vasectomy (III) Phagocytosis of sperms within the uterus
(D) Tubectomy (IV) Removal of fallopian tube
Select the correct option.
(A) (B) (C) (D)
(1) III I IV II
(2) IV II I III
(3) I III II IV
(4) II IV III I
5. Which of the following STIs are not curable? (2020-II)
(1) Gonorrhoea, Trichomoniasis, Hepatitis B
(2) Genital herpes, Hepatitis B, HIV infection
(3) Chlamydiasis, Syphilis, Genital warts
(4) HIV, Gonorrhoea, Trichomoniasis
6. In which of the following techniques, the embryos are transferred to assist those females who cannot conceive ? (2020-I)
(1) GIFT and ZIFT (2) ICSI and ZIFT
(3) GIFT and ICSI (4) ZIFT and IUT
7. Match Column-I with Column-II. (2017)
Column-I Column-II
(A) Gonorrhoea (I) HIV
(B) Syphilis (II) Neisseria
(C) Genital warts (III) Treponema
(D) AIDS (IV) Human papilloma virus
Select the correct option.
(A) (B) (C) (D)
(1) III IV I II
(2) IV II III I
(3) IV III II I
(4) II III IV I
CHAPTER TEST
1. Which of the following assisted reproductive technologies requires micropuncture of zona pellucida by an injection micropipette?
(1) ICSI (2) GIFT
(3) IUI (4) POST
2. Which of the following is an assisted reproductive technology in which the semen is directly introduced into a woman’s womb?
(1) IUT
(2) IUD
(3) IUI
(4) IVF
8. In case of a couple where the male is having a very low sperm count, which technique will be suitable for fertilisation? (2017)
(1) Gamete intracytoplasmic fallopian transfer
(2) Artificial insemination
(3) Intracytoplasmic sperm injection
(4) Intrauterine transfer
9. In context of amniocentesis, which of the following statements is incorrect ? (2016-I)
(1) It can be used for detection of Down’s syndrome.
(2) It can be used for detection of cleft palate.
(3) It is usually done when a woman is between 14-16 weeks pregnant.
(4) It is used for prenatal sex determination.
10. Which of the following is not a method of contraception? (2013-K)
(1) Condoms
(2) Pills of a combination of oxytocin and vasopressin
(3) Lippe’s loop
(4) Tubectomy
3. Given below are two statements.
Statement I : Oral contraceptive pills have to be taken daily, starting preferably within the first five days of the menstrual cycle.
Statement II : After completing a 21-day course of pills, a pill-free interval of 7 days should be observed.
In light of the above statements, choose the correct answer from the options given below.
(1) Both statement I and statement II are correct.
(2) Both statement I and statement II are incorrect.
(3) Statement I is correct but statement II is incorrect.
(4) Statement I is incorrect but statement II is correct.
4. Which of the following is incorrect regarding vasectomy?
(1) No sperm occurs in seminal fluid.
(2) Spermatogenesis stops after vasectomy.
(3) Vasa deferentia is cut and tied.
(4) Reversibility is very poor.
5. Given below are two statements. One is labelled Assertion (A) and the other is labelled Reason (R).
Assertion (A) : HIV can be transmitted from an infected mother to the foetus.
Reason (R) : HIV is a sexually transmitted infection (STI).
In light of the above statements, choose the correct answer from the options given below.
(1) Both (A) and (R) are true and (R) is the correct explanation of (A).
(2) Both (A) and (R) are true but (R) is not the correct explanation of (A).
(3) (A) is true but (R) is false.
(4) Both (A) and (R) are false.
6. A device is inserted in the uterus for contraceptive effect. Which of these effects will not be caused by it?
(1) Increasing phagocytosis of sperms
(2) Suppressing motility of sperms
(3) Preventing implantation of the blastocyst
(4) Prevents entry of sperm into the vagina
7. Select the correct set of STIs.
(1) Gonorrhoea, syphilis, chlamydiasis
(2) Hepatitis-B, HIV and trypanosomiasis
(3) Amoebiasis, ascariasis and filariasis
(4) Genital herpes, genital warts and cancer
8. Which of the following are hormonal methods of contraception?
(1) Diaphragms, cervical caps, and vaults
(2) Spermicidal creams, foams, and jellies
(3) Injections, implants, and pills
(4) Vasectomy, tubectomy, and hysterectomy
9. Assisted reproductive technologies (ARTs)
(1) manipulate gametes and embryos for the treatment of infertility
(2) help couple in voluntary termination of pregnancy
(3) aim at reducing the risk of sexually transmitted infections
(4) include methods to prevent pregnancy due to the coital act
10. Which of the following statements is/are true with regard to lactational amenorrhea?
(a) Menstruation does not occur during intense lactation.
(b) This method is of high contraceptive efficiency.
(c) It is a natural method of contraception with no side effects.
(d) The chances of conception are nil at least for two years after parturition.
(1) (a) and (c) only
(2) (b) and (d) only
(3) (a) and (b) only
(4) (c) and (d) only
11. Given below are two statements.
Statement I : All sexually transmitted infections (STIs) are completely curable.
Statement II : All STIs are transmitted by sexual intercourse and affect only reproductive organs.
In light of the above statements, choose the correct answer from the options given below.
(1) Both statement I and statement II are correct.
(2) Both statement I and statement II are incorrect.
(3) Statement I is correct but statement II is incorrect.
(4) Statement I is incorrect but statement II is correct.
12. Administration of which of the following within 72 hours of coitus could avoid possible pregnancy due to rape or casual unprotected intercourse?
(a) Progestogens
(b) Progestogen-estrogen combinations
(c) IUDs
(1) (a) or (b) only (2) (b) or (c) only
(3) (a) or (c) only (4) (a), (b) or (c)
13. Neither oestrogen nor progestogen is present in
(1) Mala-D (2) Mala-N (3) LNG-20 (4) Saheli
14. Match Column-I with Column-II.
Column-I Column-II
(A) Nonmedicated IUD (I) Vaults
(B) Copper releasing IUD (II) Lippes loop
(C) Hormone releasing IUD (III) Multiload 375
(D) Barrier (IV) LNG – 20
Select the correct option.
(A) (B) (C) (D)
(1) I II III IV
(2) II III IV I
(3) II IV III I
(4) I III IV II
15. Which of the following contraceptives are reusable?
(1) Oral pills (2) Implants
(3) Diaphragms (4) Condoms
16. Oral contraceptive pills prevent ovulation by
(1) thickening cervical mucus
(2) inhibiting the release of gonadotropins from anterior pituitary
(3) preventing the production of oestrogen from the ovary
(4) altering the endometrium of the uterus
17. Given below are two statements.
Statement I : Diaphragms, cervical caps, and vaults are barriers made of rubber that are inserted into the female reproductive tract to cover the cervix during coitus.
Statement II : They prevent conception by inhibiting ovulation and implantation.
In light of the above statements, choose the most appropriate answer from the options given below.
(1) Statement I is correct, but statement II is incorrect.
(2) Statement I is incorrect, but statement II is correct.
(3) Both statement I and statement II are correct.
(4) Both statement I and statement II are incorrect.
18. What is significance of copper ions in contraception?
(1) They delay ovulation in females.
(2) They suppress sperm motility and fertilising capacity of sperms.
(3) They increase the level of prolactin so as to suppress the activity of LH and FSH.
(4) They decrease the libido and sexual desire of female.
19. Which of the following contraceptives are very similar to each other in their mechanism of action?
(1) Cu-7 and LNG-20
(2) Implant and Multiload-375
(3) Nirodh and Saheli
(4) LNG 20 and Progestasert
20. Which of the following statements is incorrect about reproductive health?
(1) STDs are reported to be very high among persons in the age group of years 15-24.
(2) MTP has a significant role in decreasing the population though it is not meant for that purpose.
(3) Females infected with STD may often be asymptomatic and hence, may remain undetected for long.
(4) The reasons for infertility cannot be psychological.
21. Given below are two statements.
Statement I : Condoms are used to cover the penis or vagina just after coitus.
Statement II : Condoms prevent the meeting of sperm and ovum.
In light of the above statements, choose the correct answer from the options given below.
(1) Both statement I and statement II are correct.
(2) Both statement I and statement II are incorrect.
(3) Statement I is correct but statement II is incorrect.
(4) Statement I is incorrect but statement II is correct.
22. Given below are two statements. One is labelled Assertion (A) and the other is labelled Reason (R).
Assertion (A) : Day 10 to 17 of the menstrual cycle is called the fertile period.
Reason (R) : Chances of fertilisation are very high during this period
In light of the above statements, choose the correct answer from the options given below.
(1) Both (A) and (R) are true and (R) is the correct explanation of (A).
(2) Both (A) and (R) are true but (R) is not the correct explanation of (A).
(3) (A) is true but (R) is false.
(4) Both (A) and (R) are false.
23. Which of the following is not a complication of STIs (Sexually transmitted infections)?
(a) Still births
(b) Ectopic pregnancies
(c) Infertility
(d) Cancer of the reproductive tract
(e) Pulmonary inflammatory disease
(1) Only (e)
(2) Only (c) and (e)
(3) Only (d)
(4) Only (a) and (b)
24. In IVF, embryo with more than 8 blastomeres is transferred into
(1) uterus
(2) fallopian tube
(3) fimbriae
(4) cervix
25. A healthy woman has regular 28-day menstrual cycles, but her husband has low sperm counts. The best timing of IUI for this woman would be on
(1) day 3 and day 5
(2) day 26 and day 28
(3) day 12 and day 14
(4) day 18 and day 20
26. Which of the following is not a feature of an ideal contraceptive?
(1) User-friendly and easily available
(2) Effective and irreversible
(3) With no or less side effects
(4) Should not interfere with sexual drive
27. Given below are statements: one is labelled as Assertion A and the other is labelled as Reason R.
Assertion (A) : GIFT is recommended for women who have fibrioids in uterus.
Reason (R) : Fertilisation occurs in vitro in GIFT.
In the light of the above statements, choose the correct answer from the options given below.
(1) Both (A) and (R) are true and (R) is the correct explanation of (A).
(2) Both (A) and (R) are true but (R) is not the correct explanation of (A).
(3) (A) is true but (R) is false.
(4) Both (A) and (R) are false.
28. Read the following statements.
Statement I : Surgical methods of contraceptives are available for both males and females.
Statement II : Barrier methods of contraceptives are available only for males.
In the light of given statements, choose the correct answer from the options given below.
(1) Statement I is correct but statement II is incorrect.
(2) Statement I is incorrect but statement II is correct.
(3) Both statement I and statement II are correct.
(4) Both statement I and statement II are incorrect.
29. Read the following statements about diaphragms and select the correct option.
i) They are inserted by doctors or expert nurses into the uterus.
ii) They are a barrier method of contraception.
iii) They are cheap and reusable.
iv) They release progestogens that inhibit ovulation.
(1) (i) and (ii) are correct
(2) (ii) and (iii) are correct
(3) (iii) and (iv) are correct
(4) (i) and (iv) are correct
30. Which of the following is an advantage of implants over pills in contraception?
(1) They inhibit ovulation.
(2) Their effective periods are longer.
(3) They thicken cervical mucus.
(4) Protect the user from STIs.
31. Which of the following contraceptive methods is not used for spacing of births?
(1) Condoms
(2) Intrauterine devices
(3) Tubectomy
(4) Oral pills
32. Which of the following ARTs involves the transfer of ovum into the fallopian tube?
(1) ICSI (2) IVF
(3) ZIFT (4) GIFT
33. Giv en below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : MTPs are considered relatively safe during the first trimester.
Reason (R) : The first movements of the foetus are usually observed by the end of the first trimester.
In light of the above statements, choose the most appropriate answer from the options given below.
(1) Both (A) and (R) are correct and (R) is the correct explanation of (A).
(2) Both (A) and (R) are correct but (R) is not the correct explanation of (A).
(3) (A) is correct but (R) is not correct.
(4) (A) is not correct but (R) is correct.
34. Infertility cases due to oligospermia (low sperm counts in the ejaculates) could be corrected by
(1) IUD (2) IUI
(3) MTP (4) STI
35. Given below are two statements. One is labelled Assertion (A) and the other is labelled Reason (R).
Assertion (A) : The use of condoms has increased in recent years.
Reason (R) : Condoms may sometimes interfere with the sexual satisfaction of the user.
In light of the above statements, choose the correct answer from the options given below.
(1) Both (A) and (R) are true and (R) is the correct explanation of (A).
(2) Both (A) and (R) are true but (R) is not the correct explanation of (A).
(3) (A) is true but (R) is false.
(4) Both (A) and (R) are false.
36. Select the correct reasons for India’s population crossing 1.2 billion in May 2011
from the following.
(a) Increase in health care facilities
(b) Decrease in population at reproducible age
(c) Decrease in maternal mortality rate
(d) Increase in infant mortality rate
(1) (a), (b), (c) and (d)
(2) (a) and (c) only
(3) (b) and (d) only
(4) (c) and (d) only
37. Which of the following methods of birth control has maximum failure rate?
(1) Intrauterine devices
(2) Oral contraceptive pills
(3) Coitus interruptus
(4) Surgical methods
38. The age-old family planning method that requires sufficient self-control, specifically by the male partner, is
(1) locational amenorrhea
(2) periodic abstinence
(3) coitus interruptus
(4) oral contraception
39. Consider the following statements.
Statement I : Amniocentesis is used to test for the presence of certain genetic disorders.
Statement II : In aminocentesis, some of the amniotic fluid of the developing foetus is taken to analyse the foetal cells and dissolved substances.
Of the above statements, which one of the following options is correct?
(1) Both statement I and statement II are correct.
(2) Both statement I and statement II are incorrect.
(3) Statement I is correct but statement II is incorrect.
(4) Statement I is incorrect but statement II is correct.
40. Given below are two statements.
Statement I : Use of condoms has increased in recent years due to its additional benefit of protecting the user from contracting STIs.
Statement II : Both the male and the female condoms are disposable, can be selfinserted and thereby gives privacy to the user.
In light of the above statements, choose the most appropriate answer from the options given below.
(1) Statement I is correct, but statement II is incorrect.
(2) Statement I is incorrect, but statement II is correct.
(3) Both statement I and statement II are correct.
(4) Both statement I and statement II are incorrect.
41. A birth control method which is highly effective but with very poor reversibility is
(1) emergency contraceptive
(2) sterilisation method
(3) coitus interruptus
(4) periodic abstinence
42. Match Column-I with Column-II.
Column-I
Column-II
(A) Initiation of family planning program (I) 2021
(B) Legalisation of MTP (II) 2017
(C) Amendment of MTP Act (III) 1951
(D) Assisted Reproductive technologies (regulation) bill (IV) 1971
Select the correct option.
(A) (B) (C) (D)
(1) III II IV I
(2) IV III II I
(3) III IV II I
(4) III I IV II
43. Match Column-I with Column-II.
Column-I
Column-II
(A) LNG-20 (I) Contains nonoxynol-9
(B) Nirodh (II) Made from latex
(C) Multiload 375 (III) Releases progestin
(D) Spermicidal cream (IV) Releases copper
Select the correct option.
(A) (B) (C) (D)
(1) I II IV III
(2) I II III IV
(3) III II IV I
(4) II I IV III
44. Which of the following is the major difference between GIFT and ZIFT?
(1) ZIFT requires the woman to have normal fallopian tubes which is not a prerequisite for GIFT.
(2) GIFT is a non-invasive procedure while ZIFT is an invasive procedure.
(3) ZIFT involves transferring unfertilised eggs while GIFT involves transferring fertilised eggs.
(4) GIFT leads to in vivo fertilisation whereas ZIFT follows in vitro fertilisation.
45. All the following contraceptives can be used without the help of a healthcare professional, except
