Which layer of the skin contains blood vessels, sweat glands, and hair follicles?

Correct Answer: B

Rationale: The dermis, the thick layer beneath the epidermis, contains blood vessels for nutrient supply, sweat glands for thermoregulation, and hair follicles for hair growth, making it the skin's structural and functional core. The epidermis, the outer layer, is avascular and lacks glands or follicles. The hypodermis (subcutaneous tissue), below the dermis, has fat and some vessels but typically not sweat glands or hair follicles, which are dermal. 'Subcutaneous tissue' repeats hypodermis, not altering its role. The dermis's rich composition, supporting skin vitality and appendages, confirms it as the correct layer.

Correct Answer: A

Rationale: The epidermis produces new skin cells via mitosis in the stratum basale, where keratinocytes divide to replenish the upper layers, eventually forming the stratum corneum. The dermis supports with connective tissue and glands, not cell generation. The hypodermis (subcutaneous tissue) provides fat and anchoring, not new cells. The epidermis's regenerative capacity, driven by basal stem cells, sustains skin renewal, making it the correct layer.

Correct Answer: B

Rationale: The stratum basale, the deepest epidermal layer, produces new skin cells via mitosis of basal keratinocytes, regenerating the epidermis as cells move up and keratinize. Sensation involves dermal receptors, temperature regulation uses sweat and vessels, and sebum secretion is from dermal glands, not the basale. Its role as the proliferative base, sustaining skin renewal, makes it the correct primary function.

Correct Answer: B

Rationale: Fibroblasts in the dermis produce collagen and extracellular matrix during wound healing, driving repair and regeneration by rebuilding tissue post-injury. Melanocytes make melanin, not repair tissue. Macrophages clear debris and fight infection, aiding but not leading regeneration. Adipocytes store fat, not regenerate skin. Fibroblasts' role in scar formation and dermal restoration is central to skin repair, making them the key cells.

Correct Answer: C

Rationale: Arrector pili muscles generate goosebumps by contracting to raise hairs, a response to cold or emotion, historically for insulation or threat display. Melanin is from melanocytes, 'ejecting hair shafts' misrepresents their action (though they move hairs), and temperature regulation is indirect, primarily vascular/sweat-based. Goosebumps are their hallmark effect, making this the primary function.