Skin colour is determined by which pigment?

Correct Answer: A

Rationale: Skin color primarily results from melanin, produced by melanocytes in the epidermis's stratum basale. Melanin's variants eumelanin (dark) and pheomelanin (light) absorb UV light, determining skin tone from pale to dark, with higher levels in sun-adapted populations. Carotene, a yellow-orange pigment from diet, accumulates in the stratum corneum and hypodermis, subtly tinting lighter skin but not dominating color. Haemoglobin, in dermal blood vessels, adds pink or red hues, especially in fair skin, varying with oxygenation blue in cyanosis, red when flushed. While all three contribute, melanin is the primary determinant, as its concentration and distribution dictate the skin's base color, overshadowing carotene's minor role and haemoglobin's vascular effect. Dermatological research emphasizes melanin's evolutionary and protective significance, with carotene and haemoglobin as secondary modifiers, making it the key pigment in skin coloration.

Correct Answer: A

Rationale: The integument comprises the epidermis and dermis, and the stratum corneum is its most superficial layer, a dead, keratinized covering that shields the body. The papillary dermal layer is in the dermis, beneath the epidermis, not superficial. The stratum lucidum, a thin layer in thick skin, lies just below the corneum, not above it. Superficial fascia (hypodermis) is below the dermis, not part of the integument proper. The stratum corneum's position as the outermost, horny layer makes it the correct answer, consistent with its role as the skin's first line of defense.

Correct Answer: C

Rationale: The integument includes the epidermis and dermis, and the stratum corneum is the most superficial layer, a dead, keratinized barrier atop the epidermis. The hypodermis lies below the dermis, not part of the integument proper. The stratum granulosum is an epidermal layer beneath the corneum, involved in keratinization. The reticular dermal layer is deep in the dermis. The corneum's position as the outermost shield against the environment, subject to wear and shedding, confirms it as the most superficial, per skin anatomy.

Correct Answer: C

Rationale: Sweat glands, or sudiferous glands, include eccrine (merocrine), which secrete watery sweat to the skin surface, and apocrine, which secrete into hair follicles. 'Merocrine gland' is synonymous with eccrine, describing its secretion method, so it's a sweat gland. Endocrine glands, like the thyroid, secrete hormones into the bloodstream, not sweat onto the skin, making them unrelated to sudiferous glands. Apocrine glands are a distinct sweat gland type. The misfit is endocrine, as it doesn't belong to the skin's sweat-producing category, per glandular classification.

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.