Describe how the human body: • prevents pathogens from entering • defends itself against pathogens inside the body. – 7023

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1. Skin:
   Tough and dry outer layer acts as a barrier.
   Oil (sebum) on the skin repels pathogens.
   Scabs form over cuts to block entry.
   Platelets help blood clot to form scabs.
   Stomach:
   Stomach acid (HCl) kills bacteria in food or swallowed mucus.
   Eyes:
   Eyes make tears that contain enzymes to kill bacteria.
   Tears are antiseptic.
   Breathing system:
   The nose, trachea, and bronchi make mucus.
   Mucus is sticky and traps bacteria.
   Cilia move mucus out of the lungs.
   Inside the body – the immune system:
   White blood cells fight infection.
   They engulf (eat) pathogens.
   They make antitoxins to stop poisons from pathogens.

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