What pigment gives skin its color and provides some protection against UV radiation?

Correct Answer: C

Rationale: Melanin, produced by melanocytes in the stratum basale, is the pigment responsible for skin color, ranging from light to dark tones, and absorbs UV radiation to protect underlying cells from DNA damage. Melatonin, a hormone from the pineal gland, regulates sleep, not skin color. Hemoglobin, in red blood cells, gives a pinkish hue via dermal blood vessels but isn't a skin pigment or UV shield. Collagen, a dermal protein, provides structure, not pigmentation or UV protection. Melanin's dual role in coloration and photoprotection, darkening with UV exposure (tanning), makes it the correct pigment, per dermatological understanding.

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.

Correct Answer: A

Rationale: Eccrine sweat glands produce odorless sweat, mostly water, electrolytes, and waste (e.g., urea), for cooling and excretion, secreted directly to the skin surface. Apocrine glands produce thicker, odorous sweat into hair follicles. Sebaceous glands secrete sebum, not sweat. 'Merocrine' is a synonym for eccrine, but eccrine is the standard term. Their watery, non-odorous output defines their role, making this the correct type.