What are the primary functions of the skin?

• A. Protection, sensation, temperature regulation, excretion, and vitamin D synthesis.
• B. Protection, sensation, and metabolic regulation.
• C. Sensation, vitamin C storage, and immune defense.
• D. Excretion and hair growth only.

Answer: (A)

Skin performs several essential roles that keep the body protected and balanced. It acts as a strong protective barrier against pathogens, mechanical injury, and water loss. It also houses a network of nerves that provide sensation—touch, pressure, temperature, and pain—so you can respond to the environment. Temperature regulation is another key job: blood vessels in the skin widen to release heat and sweat glands produce moisture that cools the body as it evaporates. Excretion happens too, mainly through sweat, which can remove small amounts of salts, urea, and other waste products. Finally, the skin participates in vitamin D synthesis: when exposed to UVB light, the skin converts a precursor to vitamin D, which is important for calcium absorption and bone health.

Other options miss parts of these functions or overstate others (for example, vitamin C storage isn’t a feature of skin, and metabolic regulation or exclusive hair growth aren’t defining primary roles).