AP BIOLOGY

Detailed explanation-1: -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. Yet the skin hosts diverse communities of beneficial bacteria, collectively known as the skin microbiota.

Detailed explanation-2: -The innate immune system is the body’s first line of defense against germs entering the body. It responds in the same way to all germs and foreign substances, which is why it is sometimes referred to as the “nonspecific” immune system.

Detailed explanation-3: -Natural barriers include the skin, mucous membranes, tears, earwax, mucus, and stomach acid. Also, the normal flow of urine washes out microorganisms that enter the urinary tract. The immune system uses white blood cells.

Detailed explanation-4: -The epidermis, the outermost layer of the skin, is a physical barrier against pathogens.

Detailed explanation-5: -The first line of defense against infection are the surface barriers that prevent the entry of pathogens into the body. The second line of defense are the non-specific phagocytes and other internal mechanisms that comprise innate immunity.