Defending Against Infection

• Skin stops microbes getting into the body

  • Layer of dead cells form a barrier around the body
  • There is also a community of microbes on the skin (skin flora), that makes it difficult for pathogens to become established on the skin surface
• Platelets stop microbes getting into the body through a cut

  Platelets clot the blood in a cut and form a scab, keeping out microbes
• White blood cells defend against microbes in 3 ways:

  Phagocytes ingest bacteria

  1. Phagocyte detects 'foreign' microbe
  2. Phagocyte engulfs microbe
  3. Phagocyte digests microbe
• White blood cells defend against microbes in 3 ways:

  Lymphocytes produce antibodies to inactivate bacteria or viruses

  • Lymphocyte produces antibodies
  • Antibodies binds to antigen and destroy the foreign cells
  • Antigen is a molecule on the cell surface that can be recognised by the immune system