Water and many dissolved solutes are contained by blood plasma, which is a straw-colored liquid. The plasma, together with fluids derived from blood plasma (interstitial fluid and cerebrospinal fluid) serve as the extracellular environment of all of the cells in the body is the essential importance of the blood plasma. The volume, composition, and concentration of the blood plasma are finely regulated for the reason of this essential role.
It is important that the total volume and concentration of plasma in connection to the regulation of blood pressure, thirst, kidney function, and other aspects of physiology. The major solute in the plasma is the sodium ion (Na+), and the amount of plasma water is decided by its concentration (by osmosis), and therefore the blood volume. For example, eating food rich in salt (NaCl) will make you thirsty, and then you will drink, thus as a result of an increased plasma volume.
Other ions are contained by the blood plasma as well. Plasma bicarbonate (HCO3-) is a example, which is maintained within a usual range of concentrations and is needed to maintain acid-base balance. Another example is plasma potassium (K+), which must be maintained within a very narrow range of concentrations of the heart will stop beating. Common concentrations of plasma glucose, proteins, cholesterol, and other organic molecules are required for health as well.