Defence Mechanisms

• Lymphocyte = white blood cells involved in the immune response
• Self antigen = molecule on the cell surface membrane of your own body cells
• Immunity = means by which the body protects itself from infection
• Non-self antigen = antigen that is not part of the body's own tissue
• Pathogen = a microorganism that causes disease in a host organism.
• The two types of defence mechanisms are specific and non-specific
• Non specific responses are immediate and are not specific to a particular pathogen.
• Specific responses are slower and specific to each pathogen
• Examples of non specific defenses are physical/chemical barriers and phagocytosis
• Examples of specific responses are B and T lymphocytes
• Examples of barriers are skin, cilia, stomach acid and tears
• Skin

  • outer layer consists of flat, dead cells that consist mainly of the protein keratin
  • forms a tough barrier
• Cilia

  • Tiny hair-like structures lining the nose and gas exchange system
  • Bathed in mucus which is wafted to the back of the throat where it can be swallowed
• Stomach acid

  • low pH kills pathogens
• Tears

  • contain lysozymes which digest the cell walls of bacteria