AP BIOLOGY

Detailed explanation-1: -Skin, tears and mucus are part of the first line of defence in fighting infection. They help to protect us against invading pathogens. You have beneficial bacteria growing on your skin, in your bowel and other places in the body (such as the mouth and the gut) that stop other harmful bacteria from taking over.

Detailed explanation-2: -The skin is the impermeable physical/mechanical barrier that protects many pathogens from entering the body. Similarly, mucosa or mucous membranes that line the immediate internal systems help trap pathogens by producing mucous.

Detailed explanation-3: -Skin is a barrier that serves as one of the body’s first lines of defense against harmful microbes. Specialized immune cells within skin tissue help to fight invading organisms.

Detailed explanation-4: -Gut barrier function The mucus layer consists of gel produced by epithelial cells. The mucus protects the epithelial cells layer from digestive enzymes, prevents a direct contact of microorganisms and large molecules with the cells beneath while allowing small molecules to pass.