1. Constituents of Blood
• In an average healthy person, approximately 45
percent of the blood volume is cells, among
them red cells (the majority), white cells, and
platelets. A clear, yellowish fluid called plasma
makes up the rest of blood. Plasma, 95 percent
of which is water, also contains nutrients such as
glucose, fats, proteins, and the amino acids
needed for protein synthesis, vitamins, and
minerals. The level of salt in plasma is about
equal to that of sea water. The test tube on the
right has been centrifuged to separate plasma
and packed cells by density.