Platelets - Definition

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Definition


Blood platelets, or thrombocytes in medical parlance, are small cell fragments without nuclei that are produced in the bone marrow and circulate in the blood. They are implicated in the process of blood coagulation, which enables hemorrhages to be stopped. Platelets are more specifically involved in the first stage of coagulation, called primary hemostasis, where the platelets which find an area of damaged blood vessel stick to the damaged wall and secrete substances that enable them to form a thick mass of blood, called a platelet plug or fibrin plug. This plug is temporary and eventually replaced by a blood clot during the second stage, secondary hemostasis where coagulation is completed. Low platelet count is referred to as thrombocytopenia, causing high risks of hemorrhages. High platelet count indicates the presence of thrombocytosis which can heighten the risk of clots blocking the blood vessels.