Blood flow to the skin changes in response to environmental temperature. Which statement is true?

• A. It increases when environmental temperature rises
• B. It decreases when environmental temperature rises
• C. It remains unchanged
• D. It stops entirely

Answer: (A)

Blood flow in the skin increases when the environment gets warmer to help dissipate heat. When temperature rises, cutaneous vessels dilate, bringing more warm blood to the surface so heat can be lost to the surroundings through radiation, convection, and evaporative cooling (sweating). This is a key part of thermoregulation. In contrast, in cold conditions the opposite occurs—skin vessels constrict to conserve heat. The ideas that skin blood flow would decrease with heat, stay unchanged, or stop entirely don’t fit the body’s effort to maintain stable internal temperature.