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. The major solute of plasma is a heterogeneous
group of proteins constituting about 7 percent of the
plasma by weight. The principle difference between the
plasma and the extracellular fluid of the tissues is
the high protein content of the plasma. Plasma protein
exerts an osmotic effect by which water tends to move
from other extracellular fluid to the plasma. Fatty
substances (lipids) are present in plasma in suspension
and in solution. Other plasma constituents include salts,
glucose, amino acids, vitamins, hormones, and waste
products of metabolism.
