How does the skin regulate body temperature in hot weather?

The regulation of body temperature in hot weather involves several physiological responses, and dilation of blood vessels plays a crucial role in this process. When the body becomes overheated, the blood vessels in the skin expand, or dilate. This dilation increases blood flow to the surface of the skin, allowing heat to dissipate more efficiently through the skin.

As a result, the warmth of the blood is transferred to the cooler air outside, facilitating the cooling process. In conjunction with this, the body often initiates sweating—another critical mechanism for heat regulation. Sweat evaporates from the skin's surface, further cooling the body.

The other options relate to temperature regulation but do not effectively contribute to cooling the body in hot weather. Increasing body hair, for example, would be counterproductive as it would insulate the body and prevent heat loss. Additionally, reducing blood flow would lead to an increase in body temperature, as less blood would be available at the skin surface for heat dissipation. Therefore, the dilation of blood vessels is the primary process that allows the skin to cool the body in high temperatures.