Describe how the mammalian body protects itself against infections -KCSE biology essays

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Pathogenic microbes are found on the skin, respiratory tract, mouth, vagina and the intestinal tract;

The skin; has a keratinised and waterproof cornified outer layer; that provides a mechanical barrier to microbes/prevents entry of microbes.

Sebaceous gland; produces sebum; which has antiseptic properties.

The respiratory tract; produce mucus secretions that trap dust.

Cilia sweep/waft/propel the microbes to the pharynx for swallowing or to be coughed out;

Reflex actions of coughing/sneezing/vomiting help remove foreign materials from the respiratory tract/digestive tract;

Lysozymes/enzymes in saliva/nasal secretions/tears; digest walls of bacteria destroying them.

Gastric secretions such as hydrochloric acid lowers the pH in the stomach killing micro-organisms;

Clotting of blood; prevents entry of microbes after damage of blood vessels.

Phagocytosis; by phagocytes engulf and destroy microbes and other foreign bodies.

Lymphocytes are stimulated to produce antibodies; by proteins present in microbes protecting the body;

Antibodies destroy/kill micro-organisms through various ways:

Agglutinins; bind to pathogens making them clump together; killing them;

Lysins; bind to pathogens and make them burst or disintegrate;

Opsonins; bind to pathogens making them easily recognized hence be engulfed/destroyed by other lymphocytes;

Anti-toxins; bind and neutralize toxins produced by micro-organisms;

Vagina is acidic; hence making it not conducive for growth and reproduction of micro-organisms;


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