During exercise changes happen at the skin involving blood vessels and sweat glands, describe these changes.

During exercise body temperatures increase, as this can be damaging to biological processes (enzymes may be denatured) the body tries to maintain a constant body temperature in a process called homeostasis. Sweat glands and blood vessels during exercise try to reduce the body's temperature to maintain a homeostatic environment. Arterioles (which supply capillaries just under the surface of the skin) dilate and allow greater blood flow to the surface of the skin. This blood carries heat and taking it to the surface of the skin means that excess heat can be taken from the body and transferred to the environment via either conduction, convection or radiation. There is also more sweat produced by sweat glands, the sweat produced sits on the surface of the skin where the body's high temperature heats it up to the point of evaporating. Hence body heat is lost by evaporation.