Bedsores

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: 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.

Correct Answer: B

Rationale: Sweat, from eccrine glands, contains water (99%), urea, lactic acid, and salts like sodium chloride, but not calcium in significant amounts. Water is the primary component, cooling the body via evaporation. Urea, a metabolic waste, is excreted in trace amounts, reflecting sweat's minor excretory role. Lactic acid, from muscle activity, appears during exertion, lowering sweat pH. Sodium, potassium, and chloride ions maintain electrolyte balance, but calcium, critical in blood and bone, is conserved by the kidneys, not sweat glands. Analysis of sweat composition shows negligible calcium unlike urine, where it's excreted. This reflects sweat's focus on thermoregulation and minor waste removal, not mineral loss. Physiological studies confirm calcium's absence as a standard component, distinguishing it from other substances routinely detected in sweat.

Correct Answer: D

Rationale: Keratin is the fibrous protein that fills the dead cells of the stratum corneum, the outermost epidermal layer, providing toughness and resistance to abrasion. Granstein and dermin are not recognized proteins in skin anatomy likely distractors. Melanin, produced by melanocytes deeper in the epidermis, is a pigment for UV protection, not a structural filler in dead cells. Keratin, produced by keratinocytes as they move upward and die, hardens the corneum, forming a protective barrier, a process well-documented in histology as essential to skin's durability and waterproofing.

Correct Answer: B

Rationale: Melanocytes, located in the stratum basale, produce melanin, a pigment that absorbs UV radiation, protecting skin cells from DNA damage and reducing cancer risk. Darkening (tanning) enhances this shield. Keratinocytes make keratin, a structural protein, not pigment. Dendrocytes (likely dendritic cells) are immune-related, not pigment-producing. Merkel cells detect touch, not UV protection. Melanin's role in UV defense, distributed to surrounding keratinocytes, is a well-established skin adaptation, making melanocytes the correct cell type.