Human health

Introduction

The stable internal environment of our organism and its physiological and psychological balance are all very important for our general wellbeing. This state of balance is sometimes referred to as homeostasis, or simply, health. This chapter looks at human health.

Healthy human body

Health is a general condition of body and mind. It is a state of the body characterised by complete physical, mental and social wellbeing and not just by the absence of disease or injury. Health is a basic force in our daily lives. Human health is influenced by our circumstances, beliefs, culture and social, economic and physical environments.

Types of diseases

When our body cannot function properly, we say that we are sick. Our sickness is caused by diseases. A disease is a disorder of the body's functions, organs or systems. 'Disease' is actually the opposite of 'ease'. Disease is recognisable by characteristic signs and symptoms. See image 1.

Human diseases can be divided into the following main groups:

1. Inherited diseases or genetic disorders usually cannot be controlled. Normally people are born with these types of diseases, for example: Down syndrome.
2. Dietary diseases are caused by malnutrition and over eating, for example: obesity and dystrophy.
3. Infectious diseases are caused by microorganisms, for example: AIDS, influenza, chicken pox. 
4. Industrial/occupational diseases are caused by occupational hazards, for example: pneumoconiosis, repetitive strain injury.
5. Environmental diseases are caused by environmental factors, for example: lung or skin cancer.
6. Lifestyle diseases are caused by bad habits or lifestyle, for example: alcoholism.
7. Mental illnesses include serious behavioural or emotional problems, for example: schizophrenia.
8. Degenerative diseases are diseases during which the human body structure changes for the worse over time, for example: Parkinson's disease.

Epidemiology

Epidemiology is the study of the patterns, causes and prevention of human diseases. The prevalence of a disease is the number of diseased individuals at any one time (point prevalence) or over a given period (period prevalence). The incidence is the number of new cases of a disease that occur within a defined population over an established period of time.

Prevention of infections

The best way of fighting disease is its prevention. The discovery and manufacture of antibiotics and vaccines in the earlier part of the 20th century have changed the state of people's health forever. There are three stages of prevention of infections: primary, secondary and tertiary.

The primary stage - involves public educating about infectious diseases;

The secondary stage - involves treating the actual infection that has already occurred by quarantining and/or vaccinating the infected;

The tertiary stage - involves recovery from illness.

Immunity and immune response

All living organisms have a natural or acquired resistance mechanism called immunity. The immune response is general reaction of the body to substances that are foreign to it. Immunity can be active or passive. Active immunity is generated by the body in response to stimulation by a disease-causing organism or vaccine. Passive immunity is transferred to the patient passively rather than formed by the patient.

The human immune system includes all parts of the body that help in the recognition and destruction of foreign materials. White blood cells, macrophages, lymphocytes, bone marrow, lymph nodes, tonsils, thymus and spleen are all part of the immune system.

Nutrition

Nutrients are food compounds that are used by the human body to function and grow. A healthy human diet consists of fats, proteins, carbohydrates, vitamins and minerals. The right proportion between different food groups is the basis of good nutrition. The food pyramid was designed as a graphic representation of a healthy diet. See image 2.

The food pyramid shows basic food only. It does not have cooked or composite food. Food that makes up the base of the pyramid should be eaten often. Food at the top of the pyramid should be eaten in small amounts.

Vitamins

Vitamins are organic compounds that function as metabolic regulators in the body. Vitamins cannot be manufactured by the body and must be obtained through diet or supplements. Vitamins are a very important part of a healthy diet but we need them only in very small amounts.

Minerals

Minerals are inorganic elements needed for chemical reactions and for building molecules in the body. Humans need small amounts of about 25 minerals to maintain normal body function and good health.

Substance abuse

'Substance abuse' is the general term used for some lifestyle types of diseases. It involves the misuse of different chemicals (stimulants or depressants) that can alter the functioning of the mind and body. Excessive, compulsive drinking of alcohol or physical dependence on drugs that result in a chronic disorder affecting physical health and social functioning are types of substance abuse. See image 3.

Substance abuse is usually followed by substance dependence. Substance dependence is the compulsive use of different chemicals (substances). Strong emotional or psychological dependence on a substance is called an addiction.

Medically, physiological dependence on substances leads to the development of physiological tolerance. After the development of physiological tolerance, the body needs more and more of the 'abusive' substance in order to feel its effects. After a while the body becomes so dependent on these substances that it goes into withdrawal if these substances are not 'delivered' to the body's system.