Which is a notable feature of the stratum corneum layer of the integument? It:

Correct Answer: C

Rationale: The stratum corneum, the outermost epidermal layer, is composed of dead, keratin-filled cells packed tightly together, with glycolipids in the extracellular spaces acting as a waterproof sealant. This structure makes it a robust barrier against water loss, pathogens, and abrasion. Rapid division of melanocytes and keratinocytes occurs in the stratum basale, not the corneum, which is avascular and lacks blood capillaries those are in the dermis. Epidermal ridges, forming fingerprints, are in the dermis and basal epidermis, not the corneum. The keratin and glycolipid composition is a defining feature, critical to its protective role, distinguishing it from deeper, living layers.

Correct Answer: D

Rationale: Sebaceous glands secrete sebum, an oily substance, into hair follicles to lubricate hair and skin, found in the dermis. Apocrine glands secrete sweat into hair follicles, not oil. Eccrine glands secrete watery sweat directly to the skin surface via ducts. Ceruminous glands produce cerumen (earwax), not oil for hair follicles. Sebaceous glands' association with follicles and their oily output distinguish them in skin physiology, making them the correct gland type for this function.

Correct Answer: A

Rationale: The epidermis is the outermost skin layer, encompassing sublayers like the stratum corneum and germinativum, serving as the body's protective shield. The dermis lies beneath it, with the papillary dermal layer as its upper part, still deeper than the epidermis. The stratum germinativum (basale) is the deepest epidermal sublayer, not the most superficial. As a whole, the epidermis sits atop the dermis, making it the most superficial layer in skin anatomy, consistent with its role as the first barrier to the environment.

Correct Answer: C

Rationale: Transdermal administration means a drug is absorbed through the skin into the bloodstream for systemic effects (e.g., nicotine patches), not just local action (topical). Injection into the dermis is intradermal, and into subcutaneous fat is hypodermic, both distinct from surface application. 'Trans' indicates crossing the skin barrier, requiring penetration of the stratum corneum to reach circulation, a method reliant on skin permeability, making systemic action the defining feature.

Correct Answer: A

Rationale: Melanocytes in the stratum basale produce melanin, the pigment that darkens skin (tanning) upon sunlight exposure, absorbing UV to protect cell nuclei. Keratinocytes form keratin, not pigment, though they receive melanin. Dendrocytes (likely dendritic cells) handle immunity, not tanning. Lymphocytes, immune cells, aren't skin-based or pigment-related. Melanocytes' UV-responsive melanin production is the mechanism behind tanning, a protective adaptation, making them the correct cell type.