Regulation
The blood helps to keep certain values of the body in balance. For instance, it makes sure that the right body temperature is maintained. This is done both through blood plasma, which can absorb or give off heat, as well as through the speed at which the blood is flowing. When the blood vessels expand, the blood flows more slowly and this causes heat to be lost. When the environmental temperature is low the blood vessels can contract, so that as little heat as possible is lost. Even the so-called pH value of the blood is kept at a level ideal for the body. The pH value tells us how acidic or alkaline a liquid is. A constant pH value is very important for bodily functions.