Level 3 Anatomy & Physiology Training Manual MODULE 2

MODule 2 SKIN, HAIR & NAILS

SUPPORTING YOUR DREAMS & YOUR CAREER

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SKIN STRUCTURE & FUNCTIONS Skin is the largest organ of the body and is essential to our overall health and wellbeing. Healthy skin is a vital sensory organ, regulates body temperature and fluid balance, and acts as a barrier between your body and the outside world.

Skin functions as the body’s first line of defence against bacteria and viruses, and is also a vital sensory organ, sensitive to the softest touch as well as pain.

² and making up almost a sixth of our

As our largest and most visible organ, covering nearly 2m

body weight, the structure and functions of the skin are vital to our overall health and well-being.

Functions - Sensations, heat regulation, absorption, protection, excretion & secretion Three main skin layers - The Epidermis, Dermis and Subcutis – each of which is made up of several sub-layers. Appendages – such as the sebaceous glands, sweat glands and hair follicles – also exist within these layers, and they play various roles in the overall function of the skin.

EPIDERMIS As the outermost skin layer that we see and touch, the epidermis performs skin’s primary function, acting as a barrier to protect us from toxins, bacteria and fluid loss. It consists of 5 sub-layers of keratinocyte cells. The layer of the epidermis consists of 5 sub-layers of keratinocyte cells. These cells are produced in the innermost basal layer and migrate up towards the surface of the skin. As they do, they mature in shape and composition, becoming filled with keratin. This process known as keratinisation (or cornification) makes each of the sub-layers distinct.

1. Basal layer (or stratum basale): The innermost skin layer where keratinocyte cells are produced.

2. Prickle layer (or stratum spinosum): Keratinocytes produce keratin (protein fibres) and become spindle-shaped.

3. Granular layer (stratum granulosum): Keratinisation begins - cells produce hard granules and, as they push upwards, these granules change into keratin and epidermal lipids.

4. Clear layer (stratum lucidium): Cells are tightly compressed, flattened and indistinguishable from one another.

5. Horny layer (or stratum corneum): The outermost layer of the epidermis with, on average, about 20 sub-layers of flattened, dead cells depending on where on the body the skin is. These dead cells are shed regularly in a process known as desquamation. The horny layer is also home to the sweat gland pores and the openings of the sebaceous glands.

DERMIS (CORNEUM) The dermis is the thick, elastic but firm middle layer of the skin, beneath the epidermis. This skin layer’s main structural components are collagen, elastin, and connective tissues.

These provide strength and flexibility and are vital components of healthy, young-looking skin. The dermis is made up of 2 sub-layers: The lower layer (or stratum reticulare): a deep, thick area, which forms a fluid border with the subcutis.

The upper layer (or stratum papillare): forms a defined, wave-like border with the epidermis.

The dermis is also home to: Lymph vessels.

Sensory receptors.

Hair roots: the bulbous end of the hair shaft where hair is developed.

SUBCUTUS The innermost skin layer stores energy while padding and insulating the body. It is mainly composed of: Fat cells (adipocytes): clumped together in cushion-like groups.

Special collagen fibres (called tissue septa or boundaries): loose and spongy connective tissues that hold the fat cells together.

Blood vessels.

Subcutaneous fat sits underneath your skin, and its concentrations vary throughout different parts of the body. It differs to visceral fat, which accumulates around the body as a result of diet and other factors. Moreover, the distribution of fat cells also differs between men and women, as does the structure of other parts of the skin. Skin changes during a person’s lifetime.

SWEAT GLAND Your skin has two types of sweat glands:

eccrine and apocrine. Eccrine glands occur over most

of your body and open directly onto the surface of your skin. Apocrine glands open into the hair follicle, leading to the surface of the skin. Apocrine glands develop in areas abundant in hair follicles, such as on your scalp, armpits and groin.

SEBACEOUS GLANDS Each hair is surrounded by small sebaceous glands. They secreate an oilly substance known as sebum. Sebum is secreted in response to the contraction of the arector pill muscle. Sebum contains, protein, electrolytes, cholesterol & triglyceride. Sebum makes the hair more flexible and hydrated.

HAIR STRUCTURE A hair is a long, slender structure that grows out of, and is part of the skin. Each hair is made up of dead skin cells, which contain the protein keratin.

follicle and the hair shaft. The follicle is the essential unit for the generation of hair. The hair shaft consists of a cortex and cuticle cells, and a medulla for some types of hairs.

Hair is a derivative of the epidermis and consists of two distinct parts: the

Hair functions Scalp insulates against the cold, protects against the sun.

Eyebrows cushion the brow bone and prevents sweat frrom running down into the eyes.

Eyelashes help to prevent foreign particles from entering the eye.

Nostril hair traps dust particles inhaled with the air.

Ear hair protects the ear canal. The hair cells in the inner ear help to send signals to the brain when the head moves; this information is used to help the body maintain balance.

There are two types of hair, Soft Vellus hair found all over the body and Terminal Hair which is thick coarse hairs, found on your head and genital areas.

HAIR GROWTH CYCLE The first three phases — Anagen, Catagen, and Telogen cover the growth and maturation of hair and the activity of the hair follicles that produce individual hairs. During the final, or exogen, phase, “old” hair sheds, though usually, a new hair is getting ready to take its place.

Each phase has its own timeline, which can be affected by age, nutrition, and overall health. That means there are steps you can take along the way to help ensure that your hair follows a healthy growth cycle.

1.

Anagen: Growing phase

The stages of hair growth begin with the anagen phase. It’s the longest phase, lasting about 3 to 5 years for the hairs on your head, though for some people a single hair could continue growing for 7 or more years. Fortunately, the anagen phase differs with different types of hair. For example, the anagen phase for eyebrow hairs and pubic hairs is much shorter than the phase for your scalp hairs.

During the anagen phase, your hair follicles are pushing out hairs that will continue to grow until they’re cut or until they reach the end of their lifespan and fall out. At any time, about 90 percent of the hairs on your head are in the anagen phase.

2. Catagen: Transition phase The catagen phase starts when the anagen phase ends, and tends to last about 10 days or so.

During this chapter, hair follicles shrink and hair growth slows. The hair also separates from the bottom of the hair follicle, yet remains in place during its final days of growing.

Only about 5 percent of the hairs on your head are in the catagen phase at any given time.

3. Telogen: Resting phase The telogen phase typically lasts around 3 months. An estimated 10 to 15 percent of your scalp hairs are in this phase.

Hairs don’t grow during the telogen phase, but they don’t usually fall out either. The telogen phase is also when new hairs start to form in follicles that have just released hairs during the catagen phase.

THE NAIL STRUCTURE A fingernail is produced by living skin cells in the finger. A fingernail consists of several parts

nail plate (the visible part of the nail), the nail bed (the skin beneath the nail plate), the cuticle (the tissue that overlaps the plate and rims the base of the nail), the nail folds (the skin folds that frame and support the nail on three sides), the lunula (the whitish half-moon at the base of the nail) and the matrix (the hidden part of the nail unit under the cuticle). including the

Fingernails grow from the matrix. The nails are composed largely of keratin, a hardened protein (that is also in skin and hair). As new cells grow in the matrix, the older cells are pushed out, compacted and take on the familiar flattened, hardened form of the fingernail.

The average growth rate for nails is 0.1 mm each day (or 1 centimeter in 100 days). The exact rate of nail growth depends on numerous factors including the age and sex of the individual and the time of year. Fingernails generally grow faster in young people, in males, and in the summer.

REVIEW SKIN, HAIR & NAILS Here is what you have learn't about skin, hair & nails.

Skin regulates body temperature and fluid balance, and acts as a barrier between your body and the outside world.

Three main skin layers of the skin are - The Epidermis, Dermis and Subcutis.

Each of which is made up of several sub-layers. Appendages – such as the sebaceous glands, sweat glands and hair follicles.

A hair is a long, slender structure that grows out of, and is part of the skin. Each hair is made up of dead skin cells, which contain the protein keratin.

Hair is a derivative of the epidermis and consists of two distinct parts: the follicle and the hair shaft. The follicle is the essential unit for the generation of hair. The hair shaft consists of a cortex and cuticle cells, and a medulla for some types of hairs.

nagen, Catagen, and Telogen cover the growth and maturation of

The first three phases — A

hair and the activity of the hair follicles that produce individual hairs. During the final, or exogen, phase, “old” hair sheds, though usually, a new hair is getting ready to take its place.

A fingernail is produced by living skin cells in the finger. A fingernail consists of several parts

nail plate (the visible part of the nail), the nail bed (the skin beneath the nail plate), the cuticle (the tissue that overlaps the plate and rims the base of the nail), the nail folds (the skin folds that frame and support the nail on three sides), the lunula (the whitish halfmoon at the base of the nail) and the matrix (the hidden part of the nail unit under the cuticle). including the