Which of the following situations could produce life threatening fluid loss and infection?

Correct Answer: B

Rationale: Full-thickness skin burns destroy the epidermis and dermis, removing the waterproof stratum corneum and exposing underlying tissues, leading to rapid fluid loss (dehydration) and vulnerability to infection without the skin barrier. Stomach ulcers cause internal bleeding, not external fluid loss or skin infection risk. Muscle tears and bone fractures may bleed or infect, but they don't typically cause massive fluid loss like burns, as the skin remains intact. Burns' dual threat of fluid loss and pathogen entry, especially over large areas, makes them uniquely life-threatening, as seen in burn unit protocols.

Correct Answer: A

Rationale: Vitamin D production starts in the skin when UVB radiation converts 7-dehydrocholesterol in the epidermis to previtamin D3, initiating the process. PTH signals the kidneys to activate vitamin D later, not the skin. Calcium presence is an outcome, not a trigger. Hydroxylation occurs in the liver and kidneys, not the skin, modifying the skin's product. UV exposure is the essential first step, a photochemical reaction unique to epidermal cells, making this the correct initiating condition.

Correct Answer: D

Rationale: The stratum corneum, the epidermis's outermost layer, consists of dead, keratinized cells that protect against heat, chemicals, and bacteria, forming a durable barrier. Rapidly dividing cells are in the stratum basale, not corneum. Anchoring to muscle occurs via the hypodermis, not corneum. Collagen, elastin, and reticular fibers are in the dermis, not the avascular epidermis. The corneum's protective role, shedding pathogens and resisting environmental damage, is its primary function, making this the accurate description.

Correct Answer: D

Rationale: The skin protects, secretes sebum, aids immunity, regulates temperature, excretes sweat, synthesizes vitamin D, perceives stimuli, and protects all true functions. It doesn't synthesize vitamin E, which is dietary, not skin-produced. 'Social function' (e.g., appearance) is a byproduct, not a primary physiological role like temperature regulation. The inclusion of vitamin E synthesis, an incorrect function, makes this list the one with non-integumentary roles.

Correct Answer: D

Rationale: The stratum corneum, the outermost epidermal layer, protects against water loss and abrasion with its dead, keratin-filled cells and lipid barriers. The stratum germinativum (basale) generates cells, not protection. The lucidum, in thick skin, is a transitional layer, not the main shield. The corneum's role as the skin's durable, waterproof surface, constantly abraded and renewed, makes it the critical protective stratum, per epidermal function.