Non-specififc defences

• 1.A pathogen is a bacterium, virus or other organism that causes disease

  2. Epithelial cells form a physical barrier.

  3. Chemical secretions are produced against invading pathogens.

  4. Secretions include; tears, saliva, mucus and stomach acid.

  5. The inflammatory response happens when the body suffers and injury such as a cut or the

  invasion by microorganisms.

  6. Mast cells which are present in the tissues release a chemical called Histamine.

  7. Histamine causes increased capillary permeability and vasodilation
• 8.The increased blood flow leads to an accumulation of phagocytes and clotting elements at

  the site of infection.

  9. Phagocytes recognise pathogens and destroy them by phagocytosis.

  10. Phagocytosis involves the engulfing of pathogens and their destruction by digestive

  enzymes contained in lysosomes.

  11. Phagocytes release cytokines which attract more phagocytes to the site of infection

  12. Cytokines are protein molecules that act as a signal to specific white blood cells causing

  them to accumulate at the site of infection.