Active agents of inflammation when damage occurs to a blood vessel. They are not actually cells, but fragments released by megakaryocyte cells. Megakaryocyte is a large cell in the bone marrow whose function is to produce platelets. When vascular damage (i.e., damage to blood vessels) occurs, the platelets stick to the vascular walls, forming clots to prevent the loss of blood. Thus, it is important to have adequate numbers of normally functioning platelets to maintain effective coagulation (clotting) of the blood. There are drugs that can potentially alter the platelet count, making it necessary to monitor the count. Also, some persons living with HIV develop thrombocytopenia -- a condition characterized by a platelet count of less than 100,000 platelets per cubic millimeter of blood. The normal value for men is 154,000-354,000 platelets per cubic millimeter of blood. For women, it is 162,000-380,000 platelets per cubic millimeter of blood.