Which of the following is a function of the skin?

• A. Protection
• B. Digestion
• C. Oxygen transport
• D. Hormone synthesis

Answer: (A)

The main concept is that the skin acts as a protective barrier. The outer skin layer, with keratin and lipids, forms a tough, waterproof seal that prevents water loss and blocks entry by microbes and chemicals. This physical barrier is reinforced by ultraviolet protection from melanin and by immune components in the skin, such as Langerhans cells and antimicrobial peptides, which help defend against pathogens. While the skin does contribute to other functions—like temperature regulation, sensation, and even initiating vitamin D synthesis in sunlight—digestion, oxygen transport, and hormone synthesis are not functions of the skin. Digestion happens in the digestive tract, oxygen transport in the circulatory system, and hormones are produced mainly by endocrine glands (with vitamin D synthesis in the skin being a precursor step in a separate hormonal pathway). Therefore, protection is the most fundamental and characteristic function of the skin.