What is the effect of cutaneous vasodilation on heat transfer during heat stress?

• A. Decreases skin blood flow during heat stress.
• B. Little to no effect on heat transfer.
• C. Increases skin blood flow carrying more core heat to the skin surface, enhancing convective and radiative heat loss.
• D. Reduces sweating rate.

Answer: (C)

During heat stress, the body opens up cutaneous arterioles to raise skin blood flow. This brings more warm arterial blood from the core to the skin surface, increasing the temperature gradient between the body and the environment at the skin. As a result, heat transfer from core to skin to surroundings is enhanced, mainly through convection (air or liquid moving heat away from the skin) and radiation (infrared energy emitted by the skin). In short, cutaneous vasodilation acts as a larger conduit for core heat to reach the skin, where it can be lost to the environment. Evaporative cooling from sweating is another route, but the vasodilation itself primarily increases heat transfer via the skin to the surroundings.