human defence systems

• how does the skin prevent pathogens from entering the body?

  • physical barrier
  • scab formation
• how does the nose protect the body against pathogens?

  hair & mucus trap pathogens
• how does the trachea & bronchi protect the body from pathogens?

  secrete mucus to trap pathogens
• how does the stomach protect the body against pathogens?

  secretes hydrochloric acid which kills pathogens in food
• how does the immune system defend against disease?

  producing white blood cells
• what is phagocytosis?

  white blood cells engulf foreign cells & digest them
• how does antibody production prevent disease?

  • white blood cells produce antibodies
  • antibodies are complementary to a specific antigen on a pathogen
  • antibodies bind to antigens so they can be found & destroyed by other white blood cells
  • if the person is infected with the same pathogen, white blood cells can rapidly produce the antibodies to kill it - memory cells
• how does antitoxin production prevent disease?

  antitoxins bind to toxins released by pathogens & neutralise them
• how do the eyes prevent pathogens from entering the body

  produce tears which contain enzymes which kill bacteria