Water has a relatively high heat capacity, meaning it can absorb a lot of heat before its temperature rises. This trait allows the water in every cell of the human body to act as a buffer against sudden temperature changes. Blood, which is made largely of water, moves heat away from the extremities and toward the vital organs when it needs to conserve heat, it flows towards the skin surface to release excess heat when necessary, and it transports muscle heat away as needed. Water also helps expel excess heat from the body as water vapor from the lungs and sweat on the skin.