Thermoregulation via Skin Structures

Steps:

• Identify key skin structures for temperature control: sweat glands for cooling, blood vessels for heat exchange, and arrector pili muscles for insulation.
• Match to diagram: assume 1 as sweat gland (evaporative cooling), 2 as arrector pili (raises hair to trap air), 4 as blood vessels (vasodilation/vasoconstriction).
• Exclude 3, likely sebaceous gland, which lubricates but does not regulate temperature.
• Select option including 1, 2, and 4 for comprehensive thermoregulation.

Why B is correct:

• B includes sweat glands (1), arrector pili (2), and blood vessels (4), which maintain homeostasis by cooling, insulating, and adjusting heat loss per physiological principles of thermoregulation.

Why the others are wrong:

• A omits blood vessels (4), missing heat exchange mechanism.
• C excludes sweat glands (1) and blood vessels (4), ignoring cooling and vascular control.
• D includes only blood vessels (4), neglecting glandular and muscular roles.

Final answer: B