Question 1
Which of the following is not a function of the integument?
- A. prevention of body dehydration
- B. synthesis of vitamin A
- C. regulation of body fluids
- D. regulation of body temperature
Show answer and rationale
Correct answer: B — synthesis of vitamin A
The integumentary system, primarily the skin, performs several critical physiological roles. It prevents dehydration by acting as a barrier, thanks to the waterproof keratin in the epidermis, which limits water loss. It regulates body fluids indirectly through sweat production and prevents excessive fluid loss. Temperature regulation occurs via sweating and blood vessel dilation or constriction in the dermis. However, the skin does not synthesize vitamin A. Instead, it synthesizes vitamin D when exposed to ultraviolet light, using cholesterol precursors in the epidermis. Vitamin A, essential for skin health and vision, is obtained from the diet (e.g., through beta-carotene) and not produced by the integument. This distinction is key: while the skin processes certain vitamins, its synthetic capacity is limited to vitamin D, not A. Misattributing vitamin A synthesis to the skin overlooks its actual metabolic role and dietary dependency, making this the function it does not perform among the listed options.