Why does plasma contain platelets?

Plasma contains antibodies (immunoglobulins) and clotting factors. Not all components are produced from a particular unit of donated blood. For example, immunoglobulins and clotting factors may be prepared from plasma pooled together from many donors. read more

Red and white blood cells are fairly large, but platelets are almost microscopic. If the plasma is separated from the solid portion of blood by centrifuge it still may contain some platelets as they are so small and so difficult to spin off like the other blood cells. read more

This is why there are frequent blood drives encouraging people to donate blood plasma. Along with water, salt, and enzymes, human plasma also contains important components. These include immunoglobulins (antibodies), clotting factors, and the proteins albumin and fibrinogen. read more