Suppose we take a sample of blood and mix it in a tube with an anticoagulant to stop it clotting, before spinning it in a centrifuge. What now will our sample look like?
The cellular components will have sunk to the bottom of the tube – they form about 45% of the sample. The remaining 55% is the liquid we call plasma.
What does plasma consist of? Most of it is water – about 92%, whilst plasma proteins form about 7%. The remaining 1% is other dissolved solutes such as inorganic ions.