Components of Blood Whole blood comprises many cellular components suspended in the protein-rich fluid called plasma . In response to chemical messages, they proliferate and become specialized for a particular function. The red cells circulate for about 120 days, picking up oxygen as they flow through tiny blood vessels in the lung and delivering it to the tissues. Also called leukocytes, the white cells perform an assortment of janitorial and protective functions depending on their lineage. Lymphocytes are abundant, small cells that bear the major responsibility for the body's specific immune response.
Monocytes are large cells that can enter tissues where they become macrophages .
Their aggregation initiates clotting. When a person receives a transfusion, careful matching of the transfused blood to the patient's own is critical. Plasma Plasma is the fluid portion of blood that carries salts, nutrients, proteins and lipids throughout the body. Protein concentration plays a major role in maintaining blood pressure. The most abundant of the hundreds of plasma proteins is albumin .