An individual has spent too much time sun bathing. Not only is his skin painful to touch, but small blisters have appeared in the affected area. This indicates that he has damaged which layers of his skin?

Correct Answer: D

Rationale: Severe sunburn with pain and blisters indicates damage beyond the epidermis into the dermis. The epidermis, especially the stratum basale, gets UV damage first, causing redness and pain, but blisters form when fluid accumulates between the epidermis and dermis due to deeper injury, affecting dermal blood vessels and nerves. The hypodermis, a fatty layer, isn't typically involved in sunburn unless damage is extreme. Epidermis-only damage wouldn't produce blisters, and hypodermis-only is implausible. The epidermis and dermis combination matches the symptoms of a second-degree burn from sun exposure.

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 dermis contains blood vessels, among other structures, making it a complex layer. Its papillary region has capillaries nourishing the epidermis, while the reticular layer hosts larger vessels for circulation and thermoregulation. Sweat glands, originating in the epidermis, extend into the dermis, releasing sweat through ducts. Sensory nerve endings, like Meissner's and Pacinian corpuscles, detect touch and pressure, abundant in the dermis. Sebaceous glands, also epidermal-derived, reside in the dermis, secreting sebum into hair follicles. All listed elements vessels, glands, and nerves are present, but the question seeks one correct answer, often emphasizing blood vessels for their prominence in dermal function. Their role in nutrient delivery and heat exchange underscores the dermis's vascularity, a feature visible in histological sections and critical to skin physiology, distinguishing it from the avascular epidermis.

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.