Pooled blood platelets. Researcher holding a bag containing pooled donor blood platelets, or thrombocytes, suspended in blood plasma (the liquid component of blood). Platelets are blood cell fragments and are essential for blood clotting. These have been collected from a number of different donors (pooled). The platelets are separated from the other blood components by centrifugation. Platelet transfusions are used to treat patients with low numbers of platelets in the blood (thrombocytopeania), or dysfunctional platelets (thrombasthenia).