Whole blood is living tissue circulating through the heart, arteries, veins, and capillaries carrying nourishment, electrolytes, hormones, vitamins, antibodies, and oxygen to the body's tissues. Whole blood contains red blood cells, white blood cells and platelets suspended in a watery fluid called plasma.
If blood is treated to prevent clotting and permitted to stand in a container, the red blood cells, weighing the most, will settle to the bottom; the plasma will stay on top; and the white blood cells and platelets will remain suspended between the plasma and the red blood cells. A centrifuge may be used to hasten this separation process. The platelet-rich plasma is then removed and placed into a sterile bag, and it can be used to prepare platelet concentrates and cryoprecipitated antihemophilic factor (AHF).
To make platelets, the platelet-rich plasma is centrifuged, causing the platelets to settle at the bottom of the bag. Plasma and platelets are then separated and made available for transfusion. The plasma may also be pooled with plasma from other donors and further processed, or fractionated, to provide purified plasma proteins such as albumin, immunoglobulin, and clotting factors.