الفهرس 
الملخص العربى
Megakaryocyte developmentOnly 14 pages are availabe for public view
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Abstract
platelets have several
important functions. They adhere to sites of vascular Blood injury, generate biological mediators, secrete their granule contents, form multicellular aggregates and serve as a nidus for plasma coagulation reactions. In order to carry out these tasks, the platelet undergoes dramatic structural rearrangements, utilizes multiple membrane receptors, which bind small molecule mediators, adhesive glycoproteins and constituents of the vascular subendothelium, and activates a network of complex signaling pathways. All of these events occur within seconds of vascular injury. Collectively, they help to maintain the integrity of the vascular system.
In this essay, we will review both congenital and acquired platelet dysfunctions. Congenital platelet dysfunctions represent a small proportion of children who present with a bleeding diathesis. The diagnosis is often difficult to make, the clinical course can be highly variable, and the treatment is not well studied in randomized trials. Because of the rarity of these disorders, databases have become vital to current research initiatives. Continued contributions to these databases are imperative to ongoing investigative efforts.
Acquired platelet dysfunction, with or without clinically significant bleeding, is observed frequently and is associated with a plethora of pathogenic mechanisms affecting platelet adhesion, aggregation, or secretion. In many cases it can be traced to commonly prescribed and over-the-counter medications. With the popularity of herbal or natural supplements, a careful drug history is essential for the evaluation of a patient who has mucocutaneous bleeding that is suggestive of platelet dysfunction. Astute evaluation for the associated systemic disorders should be conducted. Platelets play a central role in hemostasis. Consequently, they lie at the heart of many inherited and acquired bleeding disorders and thrombotic events. The diagnosis of these disorders and monitoring of antiplatelet therapy require a thorough understanding of tests that measure platelet quantity and function.