Which is the proper sequence of epidermal layers pierced as a sliver penetrates the dermis of the hand?

Correct Answer: C

Rationale: A sliver penetrating the skin of the hand moves from the outermost epidermal layer inward to the dermis. The hand's skin is thick, containing all five epidermal layers. The sequence begins with the stratum corneum, the tough, dead, keratinized surface, followed by the stratum lucidum, a clear layer of dead cells found in thick skin. Next is the stratum granulosum, where keratinization starts, then the stratum spinosum, with its spiny, interconnected cells, and finally the stratum germinativum, the basal layer adjacent to the dermis where cell division occurs. The sliver pierces outward to inward: corneum, lucidum, granulosum, spinosum, germinativum, before reaching the dermis. This order reflects the histological arrangement of thick skin, as seen in palms and soles, where each layer's position and function (protection, transition, cell production) dictate the penetration path, aligning with anatomical descriptions.

Correct Answer: B

Rationale: Sebaceous glands are oil-producing glands typically associated with hair follicles, secreting sebum to lubricate hair and skin. They are not sweat glands, which produce sweat (eccrine and apocrine glands have different roles). They don't function in response to touch; that's more relevant to sensory receptors like Merkel cells. Nor do they release a watery solution of salt and waste that describes eccrine sweat glands. Their anatomical and functional link to hair follicles, where they empty sebum into the follicle, is a classic feature of skin histology, making this the correct association.

Correct Answer: C

Rationale: Bedsores (pressure ulcers) develop from prolonged pressure on skin, cutting off blood flow and causing tissue damage, often in bedridden patients. They're preventable by eliminating pressure points through repositioning, cushions, or mattresses, relieving compression on vulnerable areas like the heels or sacrum. Topical moisturizers may help skin health but don't treat established sores. Deep massages could worsen damage, not cause it. Dry skin isn't the cause; ischemia from pressure is. Prevention via pressure relief is a standard clinical approach, making this the correct answer.

Correct Answer: B

Rationale: Goosebumps occur when small muscles attached to hair follicles contract, causing hairs to stand upright and skin to pucker. These are the arrector pili muscles, smooth muscles in the dermis anchored to the hair follicle base and the epidermal-dermal junction. When stimulated by cold or emotion (via the sympathetic nervous system), they contract, pulling hairs erect, an evolutionary vestige from furrier ancestors to trap heat or signal threat. Sebaceous glands secrete sebum to lubricate hair and skin, not to cause goosebumps. 'Cappilary' (likely a typo for capillary) refers to blood vessels, which adjust for temperature but don't directly produce goosebumps. Collagen provides dermal strength but is a passive fiber, not a muscle. The arrector pili's action is involuntary, linked to thermoregulation and emotional response, and its distinct role in piloerection visible as goosebumps sets it apart as the key structure in this phenomenon.

Correct Answer: B

Rationale: Hair color arises from melanin, a pigment produced by melanocytes. Located in the hair follicle's bulb, melanocytes synthesize eumelanin (brown/black) or pheomelanin (red/yellow), injecting it into surrounding keratinocytes, which form the hair shaft's keratin structure. The amount and type of melanin determine color more eumelanin darkens hair, while pheomelanin lightens it. Keratinocytes, the majority cells in hair and epidermis, build the hair but don't produce pigment; they receive it from melanocytes. Langerhans cells are immune cells in the epidermis, unrelated to pigmentation. Merkel cells, at the epidermal-dermal junction, sense touch, not color. Melanocytes' role in hair, skin, and eye pigmentation is genetically regulated, with activity declining in graying hair. Histological studies of follicles confirm melanocytes as the pigment source, distinguishing them from structural or sensory cells in hair development.