Blood plasma (not to be confused with plasma as the highly energetic fourth state of matter) is the liquid portion of blood. 

Plasma serves as a transport medium for delivering nutrients to the cells of the various organs of the body and for transporting waste products derived from cellular metabolism to the kidneys, liver, and lungs for excretion. 

It is also a transport system for blood cells, and it plays a critical role in maintaining normal blood pressure. Plasma helps to distribute heat throughout the body and to maintain homeostasis, or biological stability, including acid-base balance in the blood and body.




These three test tubes show blood sediment. The plasma, which is most prominent in the centre tube, is a clear fluid. Red blood cells appear red and the pink coloration is due to the transfer of haemoglobin into the surrounding plasma.


The liquid portion of the blood, the plasma, is a complex solution containing more than 90 percent water. The water of the plasma is freely exchangeable with that of body cells and other extracellular fluids and is available to maintain the normal state of hydration of all tissues. Water, the single largest constituent of the body, is essential to the existence of every living cell.