Plasma is a straw coloured, viscous fluid constituting nearly 55 per cent of the blood. 90-92 per cent of plasma is water and proteins contribute 6-8 per cent of it. Fibrinogen, globulins and albumins are the major proteins.
Fibrinogens are needed for clotting or coagulation of blood. Globulins primarly are involved in defense mechanisms of the body and the albumins help in osmotic balance.
Plasma also contains small amounts of minerals like Na+, Ca++, Mg++, HCO3 – , Cl– , etc. Glucose, amino acids, lipids, etc., are also present in the plasma as they are always in transit in the body.
Factors for coagulation or clotting of blood are also present in the plasma in an inactive form. Plasma without the clotting factors is called serum.