ABSTRACT
Platelets are anucleate cells that are shed from the megakaryocytes in the bone marrow and live in the circulation for 7 to 9 days in man. Their principal physiological role is in the hemostatic process in which they rapidly adhere to each other and to exposed suben-dothelial structures when a blood vessel is damaged. They eventually form a “platelet plug” that causes arrest of blood loss. Formation of such platelet deposits also occurs pathologically and can cause obstruction of vessels that provide blood to vital organs, with severe or fatal results (thrombosis). The mechanisms that activate platelets in hemostasis and thrombosis are generally thought to be similar and to involve production of platelet-stimulating prostaglandins and thromboxanes within the platelets. These active substances are synthesized from eicosanoid precursors within the platelets, precursors that are covalently bound in the phospholipids of resting platelets and set free upon platelet stimulation.
