The integumenary system, which is the skin and its appendages such as hair, scales, feathers and hooves, has three mechanisms for regulating body temperature. If the body is too hot sweat glands in the skin will produce sweat that cools the surface by evaporating. If the body is too cold the hairs on the skin stand up so as to trap heat near the surface. (This is what "goosebumps" are.) Capillaries in the skin contract to reduce blood flow and conserve heat when the body is too cool and they dilate to increase blood flow when the body needs to be cooled. These are all examples of homeostasis, the tendency of the body to regulate its systems to maintain a state of balance.