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Physical vs Chemical Barriers

Physical Barriers	Chemical Barriers
Skin — continuous barrier, hard for pathogens to penetrate Mucus — traps pathogens in nose and airways Cilia — tiny hairs that sweep mucus (with trapped pathogens) to the throat Scabs — blood clots seal wounds to stop pathogens entering	Stomach acid — hydrochloric acid (pH 2) kills most pathogens Lysozyme — enzyme in tears and saliva that destroys bacterial cell walls Skin oils — create an environment hostile to microorganisms

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