The skin plays a role in protecting against harmful UV radiation by producing:

Correct Answer: B

Rationale: Melanin, produced by melanocytes, protects against UV radiation by absorbing it, preventing DNA damage and reducing skin cancer risk, darkening as a shield (tanning). Melatonin regulates sleep, not UV defense. Sebum lubricates, not protects from UV. Collagen provides structure, not photoprotection. Melanin's UV-absorbing property, distributed in the epidermis, is the skin's primary anti-radiation mechanism, making it the correct answer.

Correct Answer: C

Rationale: Meibomian glands, in the eyelids (part of the integumentary system), secrete an oily substance into tear film, lubricating the eyes to prevent evaporation and dryness. Temperature regulation involves sweat glands, tears come from lacrimal glands (not integumentary), and sweat is from sudiferous glands. Their role in eye lubrication, maintaining tear stability, makes this their primary function.

Correct Answer: C

Rationale: Venous wounds, typically venous stasis ulcers, are relatively painless compared to arterial wounds and improve (decrease) with elevation because this reduces venous pooling and pressure in the lower extremities. Arterial wounds are painful, especially with elevation, due to reduced blood flow. Plantar is a location, not a wound type, and diabetic wounds vary in pain depending on neuropathy but don't specifically decrease with elevation. Venous wounds align with the definition due to their chronic nature, mild discomfort, and response to elevation, which aids venous return, making this the correct answer.

Correct Answer: C

Rationale: An allograft is skin grafted from a donor of the same species, such as cadaver skin used in burn treatment, often as a temporary cover. A homograft is a similar term but less commonly used in modern medical contexts. An autograft is skin from the patient's own body, not a cadaver. A xenograft is from a different species (e.g., pig skin). Since the question specifies cadaver skin (human donor), allograft is the precise term for this type of graft in burn care, making it the correct answer.

Correct Answer: B

Rationale: 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.