What is the primary function of sebaceous glands in the skin?

Correct Answer: B

Rationale: Sebaceous glands, located in the dermis, primarily produce sebum, an oily substance that lubricates skin and hair, preventing dryness and aiding waterproofing. Sweat production is the role of sudiferous glands (eccrine and apocrine), not sebaceous. Melanin comes from melanocytes in the epidermis, not glands. Collagen is synthesized by fibroblasts in the dermis, not secreted by glands. Sebum's lipid-rich composition, secreted into hair follicles, distinguishes sebaceous glands' function, essential for skin and hair maintenance, making this the accurate primary role.

Correct Answer: B

Rationale: Blood vessels in the dermis regulate body temperature by dilating to release heat (vasodilation) or constricting to conserve it (vasoconstriction), aiding thermoregulation alongside sweat glands. Sweat production is glandular, not vascular. Melanin and sebum come from melanocytes and sebaceous glands, respectively, not vessels. The dermis's rich vascular network adjusts blood flow to maintain homeostasis, making temperature regulation their primary role, per circulatory-skin interaction.

Correct Answer: B

Rationale: Sweat glands, especially eccrine, primarily regulate temperature by secreting sweat for evaporative cooling and excrete waste like salts and urea, dual roles in homeostasis. Lubrication is sebum's job, melanin production is melanocytes', and UV protection is melanin's effect, not glands'. Sweat's cooling and minor excretory functions define their primary purpose, making this the accurate answer.

Correct Answer: B

Rationale: Sensation detects extreme temperature changes (thermoreceptors) and harmful stimuli (nociceptors for pain), alerting the body to potential damage. Thermoregulation adjusts temperature, lubrication moisturizes, and vitamin D synthesis uses UV, none sensing stimuli. The skin's sensory receptors, embedded in the dermis and epidermis, enable this protective awareness, making sensation the correct function.

Correct Answer: B

Rationale: The dermis maintains elasticity and prevents wrinkles via collagen and elastin fibers, which degrade with age, causing sagging. The epidermis provides a barrier, not elasticity. The hypodermis (subcutaneous tissue) insulates but doesn't directly affect wrinkles. The dermis's structural proteins, produced by fibroblasts, are key to skin firmness, making it the correct layer.