All but one of the following are sensory receptors in the skin. Which one is NOT?

Correct Answer: A

Rationale: Merkel discs (touch), nociceptors (pain), and Pacinian corpuscles (pressure) are sensory receptors in the skin, detecting environmental stimuli. The reticular dermal layer, the deeper dermis part, is connective tissue with collagen and elastin, not a receptor. It supports receptors but doesn't sense, distinguishing it from the others, which are specialized nerve endings or structures, making it the non-receptor.

Correct Answer: C

Rationale: Collagen and elastin fibers in the dermis provide strength and elasticity: collagen, abundant in the reticular layer, resists stretching, while elastin allows recoil, maintaining skin's resilience. Blood vessels supply nutrients, not structure. Sweat glands regulate temperature, not toughness. Nerve endings sense stimuli, not support. These fibers, produced by fibroblasts, form the dermis's extracellular matrix, critical for skin's durability and flexibility, making them the key components.

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.