Image credit

Image credit

ZIMSEC O Level Combined Science Notes: Disease:The body’s defence mechanisms

  • The body is equipped to deal with and defend itself against diseases and infections
  • These defends, while inadequate, are effective and essential
Some of the body's defenses. Image credit

Some of the body’s defenses. Image credit

  • Skin-is a physical barrier against all bacteria and other pathogens
  • Wax and hairs-found in the ears prevent invasion by microorganisms
  • Mucus and hairs-found in the nose trap invading bacteria and spores
  • Stomach acids-they kill bacteria in the food
  • White blood cells-some of them engulf and digest bacteria while others produce antibodies to destroy bacteria/neutralise toxins/poisons produced by bacteria
  • Tears-have a mild antiseptic to kill bacteria in the eyes
  • Blood clotting-is caused by platelets in the blood at damaged parts of the skin. This involves blood proteins in the plasma forming a network of fibres and eventually clotting. Clotting also helps prevent loss of blood.
  • Saliva-it has a cleansing action

To access more topics go to the Combined Science Notes page