What are three functions of the skin? To:

Correct Answer: C

Rationale: Skin produces melanin (via melanocytes) for UV protection, regulates temperature through sweat and blood flow, and minimizes water loss with the stratum corneum. Fat storage is in the hypodermis, not skin. Bile excretion is a liver function. Trapping air via hair aids insulation, but it's less central than the chosen trio. Keratin production and immunity (via Langerhans cells) are valid, but dendrocytes (dendritic cells) aren't produced by skin. The set of melanin, temperature regulation, and water retention captures key skin roles effectively.

Correct Answer: B

Rationale: The integumentary system includes skin (epidermis, dermis), hair, nails, and glands (sebaceous, sweat). Sebaceous glands, hair, nails, and mammary glands (skin derivatives) are all part. Apocrine glands, sebaceous glands, Merkel discs, and hair follicles are integumentary. Melanocytes, keratinocytes, Merkel cells, and dendrocytes are skin cells. Meissner's corpuscles, eccrine glands, and oil (sebaceous) glands are integumentary, but the hypodermis isn't, making this list the one with a non-integumentary element.

Correct Answer: C

Rationale: Sudiferous (sweat), mammary (milk), and sebaceous (sebum) glands are integumentary, located in the skin or derived from it. The pineal gland, in the brain, secretes melatonin and isn't part of the skin or integumentary system. Its endocrine role contrasts with the exocrine functions of skin glands, excluding it from the integument, making it the correct non-integumentary choice.

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: Eccrine sweat glands produce sweat mainly of water and electrolytes (e.g., sodium, chloride), secreted to the skin surface for cooling and minor waste excretion. Sebum, an oily lipid mix, is from sebaceous glands. Melanin is a pigment, not in sweat. Blood plasma, while fluid, contains proteins and cells not found in eccrine sweat, which is filtered and simpler. This watery, salty composition enables evaporative cooling, distinguishing eccrine sweat's role in thermoregulation, making it the correct answer.