Human Defences Response

• Physical Barriers: Physical characteristics of a human that prevent the spread of pathogens.
• Examples of Physical Barriers:

  • Skin- prevent pathogen reaching tissues
  • Hair and mucus in the nose- traps pathogen and expels it
  • Cilia and mucus in the trachea/bronchi- traps pathogen and expels it
• Examples of Chemical Barriers:

  • Stomach acid- kills pathogens
  • Tears - contain enzymes to breakdown pathogens
  • Mucus (both nose and trachea)- traps pathogens and expels it
  • Saliva- contains enzymes that breakdown pathogens
• The immune system have White Blood Cells to protect the body ftom pathogens
• 2 types of WBCs are Lymphocytes and Phagocytes
• Phagocytes conduct phagocytosis to engulf and digest pathogens
• Lymphocytes produce antibodies that bind to antigens and destroy them , remembering the pathogen's antigens
• Phagocytosis

  1. Pathogen invades body
  2. Phagocyte engulfs pathogen
  3. Releases enzymes to digest and destroy it

  
• Lymphocytes

  1. Lymphocytes produce antibodies, specific to an antigen
  2. Pathogen is now marked for other WBC to destroy them OR destroys them depending on the type of WBC