Aids to Health

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Immunity is the resistance to the onset of a disease after infection by harmful germs. It is the body's defence against disease and helps render harmful substances harmless.

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The body has a local defence system that starts working instantaneously. It does not depend on previous exposure and works against a wide range of infectious agents.

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They enter directly through the skin, through mucous membranes, through food or water, and through the air breathed in.

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The outer tough layer of skin is made of keratin and is almost impermeable to germs. If the skin is cut or scratched, germs can enter more easily.

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Diapedesis is the squeezing of white blood cells out of capillary walls to reach the infection site. Phagocytosis is the engulfing of germs by these white blood cells.

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Pus is a mixture of destroyed germs, killed white blood cells, and damaged tissue cells.

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The immune system deals with germs after they have entered the body tissues. It uses special proteins and cells to fight them and provide protection.

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Antibodies are special proteins belonging to the class of immunoglobulins. They are produced by specialised lymphocytes in response to antigens and are found in blood, lymph, spleen, and lymph nodes.