Class 9 science why do we fall ill disease and its causes

Why do we fall ill? – Disease and its causes – NCERT – CBSE Class 9 Science Here we will discuss 9th Class Science topic – ‘Disease and its causes’ from Why do we fall ill chapter?

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Disease and its causes The disease can be defined as a malfunctioning of the normal state of the living organism that disturbs or modifies the performance of the vital functions. There can be many reasons for diseases. Let us understand the sources of diseases.

Sources of disease There are various factors, causes or sources. Let us discuss them in detail:-

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Intrinsic or internal factors– The diseases that occur within the human body recalled intrinsic factors. The factors which affect human health are as below:-

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Malfunctioning of various body parts such as heart, kidney, liver etc.

Genetic disorder Hormonal imbalance Allergy-it means malfunctioning of the immune system of the body.

The diseases caused by internal factors are called metabolic diseases. Few examples are

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Cardiac failure (heart attack) Kidney failure Osteoporosis Myopia Cataract Sickle cell anaemia Cancer Arthritis

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Asthma Diabetes Haemophilia

Let us classify some disease of humans: Type of diseases Physical Infectious Deficiency Inherited Degenerative Mental Social

Causes of diseases Temporary or permanent change to body parts Attack by organism like viruses, bacteria, fungi, insects etc.

Inadequate diet Defective genes passed from one generation to another Organism and tissues wore away with age Bram damage or psychological Social interaction with family friends and strangers

Examples Bone fracture, leprosy Typhoid, polio, cholera etc.

Scurvy, goitre Haemophilia, anemia Arthritis, poor sight Depression Smoking, alcoholism etc

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Extrinsic or external factors-The disease-causing external agents which enter the human body by external force is known as extrinsic factors. The major factors which affect human health are

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Environment pollution-various pollutants such as gases, particulate matter, industrial chemicals, heavy metals contribute to ailments A microorganism which causes disease-microorganism such as a virus, bacteria, fungi, worms etc is transferred to the human body through air, water, food, physical contact etc.

Unbalance diet Tobacco, alcohol and drugs etc leads to chronic diseases

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Diseases caused by these factors are

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Pneumonia Leprosy Tetanus Diarrhoea Food poisoning Watch and learn Diseases and its causes with animated videos Class 9 Science.

Level of immediate causes

There are various immediate causes like virus infection is an immediate cause. Lack of good nourishment becomes the second cause. Poverty becomes an important cause; genetic difference also plays an important role in contributing to the causes of disease.

In the upcoming articles for 9th class science we will discuss types of diseases.

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