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platelet
(plātīlәt)
the smallest of the formed elements of the blood, a disk-shaped, non-nucleated cell with a fragile membrane, formed in the red bone marrow by fragmentation of megakaryocytes. Platelets tend to adhere to uneven or damaged surfaces, and there are an average of about 250,000 per mm3 of blood. The bone marrow produces from 30,000 to 50,000 platelets per mm3 of blood daily, which means that in any ten-day period all the platelets in the body are completely replaced. Called also
thrombocyte.
platelet factors
factors important in hemostasis that are contained in or attached to the platelets. Platelet factor 1 is adsorbed factor V from the plasma; platelet factor 2 is an accelerator of the thrombin-fibrinogen reaction; platelet factor 3 is a lipoprotein with roles in the activation of both factor X and prothrombin; and platelet factor 4 is capable of inhibiting the activity of heparin.
Copyright 2007. An Elsevier publication. All rights reserved.
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