Which blood vessel type can widen or narrow to regulate heat loss from the body?

Which blood vessel type can widen or narrow to regulate heat loss from the body?

• A. Dermis
• B. Capillaries
• C. Subcutaneous Tissue
• D. Hair Follicle

Answer: (B)

Regulating heat loss relies on changing blood flow to the skin. Capillaries are the vessels where heat exchange with the environment happens, and they can widen or narrow to adjust how much heat leaves the body. When the body needs to cool down, the vessels feeding the capillary beds dilate, increasing surface blood flow and promoting heat loss through radiation, convection, and evaporation. When conserving heat, they constrict, reducing surface blood flow and limiting heat loss. The other options aren’t blood vessels that regulate heat loss—those are skin layers or structures rather than vessels involved in vasomotion.

Regulating heat loss relies on changing blood flow to the skin. Capillaries are the vessels where heat exchange with the environment happens, and they can widen or narrow to adjust how much heat leaves the body. When the body needs to cool down, the vessels feeding the capillary beds dilate, increasing surface blood flow and promoting heat loss through radiation, convection, and evaporation. When conserving heat, they constrict, reducing surface blood flow and limiting heat loss. The other options aren’t blood vessels that regulate heat loss—those are skin layers or structures rather than vessels involved in vasomotion.