SWEATING - More sweat is secreted from the sweat glands when the body's too hot. The water in sweat evaporates from the surface of the skin and takes heat from the body. Therefore cooling the skin.
HAIRS LIE FLAT - Mammals have a layer of hair that provides insulation by trapping air (air is a poor conductor of heat). When it is hot, erector pili muscles relax so the hairs lie flat. Less air is trapped, so the skin is less insulated and heat can be lost more easily.
VASODILATION - When it's hot, arterioles near the surface of the skin dilate (vasodilation). More blood flows through the capillaries in the surface layers of the dermis. This means more heat is lost from the skin by radiation and the temperature is lowered.
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