IMMUNITY
Immunity means body's defence against diseases.
Germs may enter our body through-
Skin
Mucous membranes of eyes, nose, genital tracks, etc.
Food or water
Air we breathe
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Defense system has 2 levels-
Protective mechanical barriers
Thrown out if entered
Germ killing decretions
Germ fighting WBCs
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Immune system- it deals with germs after they have entered into the body tissues
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LOCAL DEFENSE SYSTEM-
Skin- it is the outer tough layer is made up of keratin and it is impermeable to germs. Clotting of blood plugs the cut ends of blood vessels so it would prevent germs.
Hair- intercept the germs journey inwards or upto the skin. Inside the nostrils trap dust containing germs.
Mucus- slimy secretion of epithelial lining of various organs like nose, etc.
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Coughing, vomiting and sneezing are direct methods to throw out germs. Even diarrhea helps in throwing out the germs in digestive tract.
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Saliva sweat, tears and nasal secretions contain germ killing substances.
HCl secreted by stomach kills germs that enter with food.
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They fight the any germ or microbe which enters the body. They are squeezed out of capillaries and engulf bacteria and destroy them.
\n Merits of local defense system-
Start working instantaneously
Not dependent on previous exposure to infections
Effective against wide range of potentially infectious agents.
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IMMUNE SYSTEM-
Immunity is the resistance to the onset of a disease after the infection by the harmful germs. Or capacity of our body to deal with foriegn substances.
Kinds of immunity-
Non specific- a degree of natural resistance to all the infections.
Specific- a natural resistance to a particular kind of germ only. Some individuals do not suffer from certain infectious diseases.
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Actively acquired immunity- infection developed by an individual due to previous disease or antigen which enter naturally leading to- naturally acquired or introduced artificially- artificially acquired. In either case lymphocytes or WBCs in the body react in 2 ways-
It is long lasting carried out through memory lymphocytes.
Passively acquired- immunity provided by outside in form of ready made antibodies. Types-
Naturally- readymade or prepared mothers antibodies may reach the foetus through placenta.
Artificially- antibodies produced in the blood of a horse or some other animal by injecting germs into its body. Antiserum injection are prepared.
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Antibodies-
They are special chemicals found in the blood which act against the germs or their secretions. Characteristics-
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