ICSE Class 8 Biology Oxford Chapter 04 Health and Hygiene

Health and Hygiene

Learning Outcomes

Non-communicable and communicable diseases

Transmission of diseases

Fever and allergies

Bites, stings, and burns

First aid

Prevention of diseases

Unhealthy habits

Observe pictures (a) to (c) carefully. Why do you think the boy fell ill? An illness or disease is a state in which an organ or a function of the body is no longer in a healthy condition. In this chapter you will learn about different types of diseases and their causes. You will also learn how most diseases can be prevented. Let us start by learning about the types of diseases.

Types of Diseases

Diseases are mainly of two types: non-communicable and communicable.

Non-communicable Diseases

Non-communicable diseases or non-infectious diseases are those that cannot be transmitted or passed from one person to another. Deficiency diseases, metabolic diseases, and hereditary diseases are examples of non-communicable diseases.

Deficiency Diseases

You must have learnt about different classes of food and their importance in class 7. Different classes of food (such as proteins, carbohydrates, vitamins, and minerals) are essential for normal functioning of the body.

Lack of proteins, carbohydrates, vitamins, and minerals in the diet can lead to deficiency diseases.

Deficiency of Proteins

A severe deficiency of proteins in children may lead to a disease called kwashiorkor (Fig. 4.1).

Most victims of this disease are children aged less than one year who are deprived of the mother's milk too early because of the arrival of a new baby ("kwashiorkor" means "the rejected one"). While the newborn is breast-fed, the older child, who still requires a protein-rich diet (in the form of mother's milk), receives a diet that does not supply enough proteins.

Symptoms

1. Stunted growth

2. Discoloured hair and skin

3. Large belly that sticks out (protrudes)

4. Oedema (swelling caused by accumulation of fluid in the tissues under the skin)

Deficiency of Proteins and Carbohydrates

A deficiency of both proteins and carbohydrates in infants results in a disease known as marasmus (Fig. 4.2).

Symptoms

1. Thin, wrinkled arms and legs

2. Sunken eyes

3. Protruding rib-cage

4. Mental retardation

Deficiency of Vitamins and Minerals

You must have learnt about vitamins and minerals in class 7. Names of common vitamins and minerals, their functions, and deficiency diseases are summarized in Table 4.1.

Metabolic Diseases

Metabolic diseases are caused by the malfunctioning of an organ or organ system or by an imbalance of certain control mechanisms of the body. For example, asthma is caused by the hypersensitivity of the epithelium lining the lungs; diabetes is the result of an imbalance of the control mechanisms that regulate carbohydrate metabolism; and cancer is the result of uncontrolled cell division.

Let us consider diabetes. A healthy body maintains a constant blood sugar level which is normally 80 mg per 100 ml of blood. When large quantities of glucose enter the blood stream, as happens after a meal, the excess glucose is converted into an insoluble product called glycogen which is stored in the liver and muscles of the body for future use. As and when required, glycogen is reconverted into glucose and reintroduced into the blood stream. All these processes are controlled by a hormone called insulin, produced in the pancreas by special cells called the islets of Langerhans. If this hormone is not produced in sufficient quantities, excess sugar cannot be stored and utilized. As a result, sugar continues to accumulate in the blood, till it is lost through urine. This leads to hunger, thirst, and gradual loss of weight-a condition referred to as diabetes. Although this condition cannot be cured, it may be kept under control by regular doses of insulin (Fig. 4.3).

A malfunctioning heart could be a disaster. Improper blood supply to the cardiac muscles, may eventually result in heart failure as these muscles do not receive enough food and oxygen.

Malfunctioning of kidney, another important organ, could also spell disaster, if it fails to remove the toxic substances that are produced within the body during metabolism. Accumulation of toxic substances above a certain level in the blood is fatal. It may be recalled that the main function of the kidney is to filter out the toxic metabolic wastes and to eliminate them from the body through the urine.

Diseases resulting from hormonal imbalance can make a person abnormally tall (Fig. 4.4(a)) or short (Fig. 4.4(b)).

Hereditary Diseases

Hereditary diseases (inherited from parents, e.g., hemophilia-a condition in which the blood flowing from a wound fails to clot), mental illnesses, and certain allergies are also non-communicable diseases.

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