Which layer contains adipose tissue?

Correct Answer: C

Rationale: Adipose tissue, a type of connective tissue rich in fat cells, is found in the hypodermis, the deepest layer of the integumentary system. The hypodermis, also called the subcutaneous layer, lies beneath the dermis and serves as an energy reserve, insulator, and cushion for underlying structures like muscles and bones. The dermis, above the hypodermis, contains dense connective tissue with collagen and elastic fibers, blood vessels, and glands, but not significant adipose tissue. The epidermis, the outermost layer, is composed of stratified squamous epithelium, a keratinized tissue focused on protection, not fat storage. 'Stratified Squamous' as an option likely refers to the epidermis's tissue type, not a distinct layer, and lacks adipose tissue. The hypodermis's fat content varies by body region and individual, but its role in lipid storage is consistent, distinguishing it from the dermis's structural support and the epidermis's barrier function. This anatomical arrangement ensures the skin's protective and metabolic roles are compartmentalized effectively.

Correct Answer: B

Rationale: Skin fibers, primarily collagen in the dermis, are arranged in bundles called lines of cleavage (or Langer's lines). These parallel alignments reflect the natural tension and orientation of collagen and elastic fibers in the reticular dermis, giving skin strength and flexibility. Surgeons use these lines for incisions, as cuts along them heal with less scarring due to minimal fiber disruption. The zone of hyperaemia is a region of increased blood flow, not a fiber structure. Epidermal ridges, on the epidermis, form fingerprints from dermal papillae, not fiber bundles. The stratum lucidum, an epidermal layer in thick skin, consists of dead cells, not fibers. Lines of cleavage are a dermal feature, visible in histological sections as organized collagen, critical for skin's mechanical properties and surgical outcomes, distinguishing them from epidermal or vascular terms.

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: C

Rationale: The stratum germinativum, also called the stratum basale, is the deepest epidermal layer where keratinocytes rapidly divide via mitosis to replenish the epidermis, replacing cells lost from the surface. The stratum lucidum, in thick skin, is a thin, dead layer above the basale, not dividing. The papillary and reticular dermal layers are in the dermis, containing connective tissue, not keratinocytes. The germinativum's name (from 'germinate') reflects its role as the regenerative base, a key feature of epidermal renewal confirmed by histological studies.

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.