Which is the outermost layer of the skin?

Correct Answer: B

Rationale: The epidermis is the outermost skin layer, encompassing sublayers like the stratum corneum, serving as the body's primary barrier. The dermis lies beneath it, supporting with connective tissue and glands. The stratum lucidum is an epidermal sublayer below the corneum in thick skin. The reticular dermal layer is deep in the dermis. As the topmost structure, the epidermis literally 'over the dermis' is the correct outermost layer, per standard skin anatomy.

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: 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: 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.