Final answer:
Blood flow in the skin helps maintain body temperature by widening or narrowing blood vessels (vasodilation or vasoconstriction) to either release more heat or conserve it in hot and cold conditions, respectively, while sweat evaporation also aids in cooling the body.
Step-by-step explanation:
In very hot conditions, the cardiovascular system and the skin collaborate to maintain a constant body temperature through a process called thermoregulation. When you feel hot, your brain sends signals to the blood vessels in your skin to undergo vasodilation, meaning they widen. This allows more blood and heat to be brought to the surface of the skin, where it can be released into the environment. Moreover, this increase in blood flow to the skin activates the sweat glands, leading to increased sweat production. As sweat evaporates, it takes heat away from the body, aiding in cooling you down. In contrast, when the body temperature is decreasing, the blood vessels in the skin undergo vasoconstriction, where they narrow to minimize blood flow near the skin's surface, thereby reducing heat loss and keeping the body warm.