According to the World Health Organization, health is defined as the state of complete physical, mental and social well-being and not merely the absence of disease or infirmity. In short, health is birth right of humans.
Health is related to the metabolic and functional efficiency of living organisms.
Hygiene is a science of rules of health.
Requirements good health-
1. we have hygienic balanced diet
2. clean drinking water
3. personal and community hygiene
4. regular physical exercise
5. knowledge about diseases and their effect on body
6. proper disposal of waste and control of vectors.
The human body has ability to resist infectious agents like bacteria, viruses, foreign bodies.
The system which protects us from various infectious agents, is called immune system. Resistance is the ability to prevent the damage or disease, through our defense mechanism.
Immunity:
The term ‘immunity’ has traditionally referred to as the resistance exhibited by the host towards injury caused by pathogens and their products.
Protection against infectious diseases is only one of the many consequences of immune response, which is entirely concerned with the reaction of the body against any foreign antigen.
The concept of immunity is believed to be started by Edward Jenner in England. He developed cowpox vaccine for the protection against the attack of small pox (virus).
Immunology is a branch of science which deals with the study of immune system, immune responses to foreign substances and their role in resisting infection by pathogens.
· The most important characteristic of immune system is that it distinguishes self (body’s own cells) and non-self (foreign molecules or invading cells). So, the immune system differentiates between the body cells and the invaders.
· Any foreign substance invading body and capable of stimulating an immune response, is called an antigen. The protective chemicals produced by immune cells in response to antigens are called antibodies.
A. Types of immunity:
There are two types of immunity –
i. Innate or Inborn (inherited) immunity
ii. Acquired or Adaptive immunity.
i. Innate immunity or Inborn immunity:
1. Innate immunity is the resistance to infections that an individual possesses by virtue of his or her genetic make-up.
2. It is the natural (inborn) defense system of the body.
3. It is not affected by prior contact with microorganisms or immunization.
4. It is nonspecific, when it indicates a degree of resistance to infection in general, or specific where resistance to a particular pathogen is concerned.
5. One form of innate immunity is formed by various types of barriers which prevent entry of foreign agents into the body.
a. Epithelial surface: The intact skin and mucous covering the body, protect it considerably against invasion by microorganism(s).
1. The healthy skin stops bactericidal activity due to the presence of high concentrations of salt in drying sweat.
2. Sebaceous secretions and long chain of fatty acids have bactericidal and fungicidal properties.
