Biology / Unit 13 Bio 3259 short lesson, about 20 seconds
Innate Immunity: Physical and Chemical Barriers
Captions available
The idea
Innate immunity's first line of defense comprises physical and chemical barriers — skin, mucus, stomach acid, antimicrobial secretions — blocking pathogens before an internal response is needed.
In practice
Stomach acid's low pH, per Bio 2775, destroys many ingested pathogens before the intestine.
Where people slip
These barriers act nonspecifically, unlike the adaptive response covered later in this chapter.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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