What is the secretion produced by sudiferous glands?

Correct Answer: A

Rationale: Sudiferous glands (sweat glands) produce sweat, either watery (eccrine) or thicker (apocrine), for thermoregulation and excretion. Sebum is from sebaceous glands, cerumin (cerumen) from ceruminous glands, and 'merocrin' is a typo or misnomer (merocrine describes eccrine secretion mode, not a substance). Sweat's role as the sudiferous output, distinct from other glandular products, confirms it as the correct secretion.

Correct Answer: C

Rationale: Melanocytes, in the stratum basale, produce melanin pigment, which colors skin and protects against UV radiation by absorbing it, reducing DNA damage. Temperature regulation involves sweat glands and vessels, not melanocytes. Sweat is from sudiferous glands, not pigment cells. Hair follicle nourishment comes from dermal blood and sebum, not melanocytes. Melanin's role in pigmentation and photoprotection, distributed to keratinocytes, defines their primary function, a vital epidermal process.

Correct Answer: D

Rationale: Vitamin D synthesis occurs in the skin when UV light converts 7-dehydrocholesterol in the epidermis to previtamin D3, essential for calcium absorption. Thermoregulation uses sweat and vessels, sensation involves receptors, and excretion removes waste via sweat, none involving UV-driven synthesis. This photochemical process, unique to skin, distinguishes vitamin D production as a key function, making it the correct answer.

Correct Answer: A

Rationale: The epidermis contains Langerhans cells, dendritic immune cells in the stratum spinosum, which detect pathogens and initiate immune responses, aiding protection. The dermis has macrophages and mast cells, but the question emphasizes the layer with these cells as a primary feature, pointing to the epidermis's barrier role. The hypodermis (subcutaneous tissue) lacks significant immune cells. The epidermis's immune function, via Langerhans cells, makes it the correct layer.

Correct Answer: B

Rationale: The subcutaneous tissue (hypodermis) is rich in connective tissue, including adipose (fat) and loose areolar tissue, binding skin to underlying structures while cushioning. Muscle tissue is deeper, nervous tissue is sparse (mostly nerves traversing), and epithelial tissue forms the epidermis, not hypodermis. Connective tissue's dominance, supporting fat and vessels, defines its composition, making this the correct type.