Which is the deepest layer of the integument?

Correct Answer: B

Rationale: The integument comprises the epidermis and dermis, with the dermis as the deeper layer, including the papillary and reticular sublayers. The epidermis is superficial, with the stratum corneum as its topmost part. The papillary dermal layer is the upper dermis, not the deepest. The dermis, extending beneath the epidermis to the hypodermis boundary, is the integument's deepest component, housing glands and connective tissue, making it the correct answer.

Correct Answer: A

Rationale: The epidermis grows hair and nails via specialized structures: hair from follicles' matrix cells in the epidermal root, and nails from the nail matrix, both derived from epidermal keratinocytes. The dermis supports follicles with connective tissue and vessels but doesn't grow them. The hypodermis (subcutaneous tissue) provides fat and anchoring, not growth. The epidermis's role in generating these keratinized appendages, through cell division in basal layers, makes it the correct layer, per integumentary development.

Correct Answer: C

Rationale: The integumentary system's primary function is protection, shielding the body from pathogens, UV radiation, and physical damage via the skin, hair, and nails. Nutrient storage occurs in the hypodermis, a secondary role. Sensation, via receptors, is important but not primary. Gas exchange is the respiratory system's job, not skin's. Protection, encompassing barriers like the stratum corneum and immune responses, defines the system's core purpose, making it the correct answer.

Correct Answer: B

Rationale: Arrector pili muscles contract to pull hair shafts upright, historically aiding insulation or threat display, though 'ejecting' is imprecise modern texts favor 'generating goosebumps.' Sweat production is glandular, heat generation isn't their role (vasculature handles that), and collagen comes from fibroblasts. Their action on hair shafts, causing piloerection, aligns with this option's intent, making it the closest match despite terminology debate.

Correct Answer: A

Rationale: Thermoregulation involves sweating (eccrine glands) and blood vessel dilation/constriction in the dermis to manage heat loss or retention, maintaining body temperature. Sensation detects stimuli, lubrication uses sebum, and vitamin D synthesis relies on UV, not temperature control. This dual mechanism of sweat evaporation and vascular adjustment defines thermoregulation, making it the correct function.