Question

Unbroken skin poses a substantial barrier to microbes. All of the following contribute to this barrier except _____________.

A. the tightly-packed layer of dead, keratinized cells
B. dryness of the skin
C. fatty acids within sebum
D. complement proteins found in perspiration

Answer 1

D. complement proteins found in perspiration.

Complement proteins found in perspiration actually contribute to the immune defense of the skin, rather than the physical barrier. The other options listed all contribute to the physical barrier of the skin, which helps to prevent microbes from entering the body. The tightly-packed layer of dead, keratinized cells prevents microbes from penetrating deep into the skin, while dryness of the skin can make it difficult for microbes to grow and multiply. Fatty acids within sebum also have antimicrobial properties, helping to prevent the growth of bacteria and fungi on the skin.

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