Which of the following is a function of the nails in the integumentary system?

Correct Answer: D

Rationale: Nails, hardened epidermal extensions, aid manipulation and gripping by providing a rigid surface for fingertips, enhancing dexterity and tool use. Temperature regulation involves sweat and vessels, not nails. Sensation occurs via skin receptors, not nails themselves. UV protection is melanin's role, not nails'. The nails' mechanical support, protecting fingertips and assisting in tasks like scratching or picking, makes manipulation their key function, a practical role in the integumentary system.

Correct Answer: C

Rationale: Excretion via skin involves sweat glands eliminating waste like salts, urea, and water, a minor but real function alongside thermoregulation. Thermoregulation cools via sweat evaporation, sensation detects stimuli, and protection shields from harm, but only excretion directly addresses waste removal. This process, though secondary to kidney function, occurs through eccrine glands, making it the correct function.

Correct Answer: A

Rationale: The epidermis is primarily keratinocytes, epithelial cells that produce keratin, forming its stratified layers from basale to corneum, comprising about 90% of its cells. Fibroblasts, in the dermis, make collagen. Adipocytes, fat cells, dominate the hypodermis. Chondrocytes form cartilage, not skin. Keratinocytes' prevalence and role in barrier formation define the epidermis, making them the correct cell type.

Correct Answer: B

Rationale: Collagen, abundant in the dermis's reticular layer, provides strength and resilience, resisting stretching and supporting skin structure, produced by fibroblasts. Melanin is an epidermal pigment, keratin fills epidermal cells, and sebum is an oily secretion, none structural in the dermis. Collagen's fibrous network, paired with elastin, ensures skin durability, making it the main protein.

Correct Answer: B

Rationale: The dermis contains blood vessels that dilate (to release heat) or constrict (to retain heat) in response to temperature changes, aiding thermoregulation. The epidermis is avascular, the hypodermis (subcutaneous tissue) has fewer vessels and focuses on insulation, not active regulation. The dermis's vascular network, adjusting blood flow, makes it the correct layer.