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Platelets or thrombocytes are the blood cells that are involved in the cellular mechanisms of primary haemostasis that lead to the formation of blood clots. Low levels or dysfunction predisposes for bleeding, while high levels, although usually asymptomatic, may increase the risk of thrombosis.

Anatomy


Like red blood cells, platelets are anuclear (no cell nucleus) and discoid (disc shaped); they measure 1.5–3.0 μm in diameter. The body has a very limited reserve of platelets, so they can be rapidly depleted. They contain RNA, a canalicular system, and several different types of granules; lysosomes (containing acid hydrolases), dense bodies (containing ADP, ATP serotonin and calcium) and alpha granules (containing fibrinogen, factor V, vitronectin, thrombospondin and von Willebrand factor), the contents of which are released upon activation of the platelet. These granule contents play an important role in both hemostasis and in the inflammatory response.

Physiology


Production

Platelets are produced in the bone marrow; the progenitor cell for platelets is the megakaryocyte. This large, multinucleated cell sheds platelets into the circulation. Thrombopoietin (c-mpl ligand) is a hormone, mainly produced by the liver, that stimulates platelet production. It is bound to circulating platelets; if platelet levels are adequate, serum levels remain low. If the platelet count is decreased, more thrombopoeitin circulates freely and increases marrow production.

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Couple honored for donating blood platelets for 17 years http://twa.lk/8Y9tS
Life_Health (Life Health) Fri, 25 Dec 2009 19:54:10 -0000
Couple honored for donating blood platelets for 17 years http://twa.lk/8Y9tS
Dad's white blood cell count improved an amazing 50% over yesterday, his platelets are higher and his hemoglobin is normal. Amazing!!
RickSandoval (+Rick Sandoval) Fri, 25 Dec 2009 18:47:41 -0000
Dad's white blood cell count improved an amazing 50% over yesterday, his platelets are higher and his hemoglobin is normal. Amazing!!
I'm like Santa today, giving the gifts of PRBCs, platelets, and plasma to the good little boys and girls...
happyfish103 (Elizabe
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Meta Description: [ There is a significant, ongoing need for blood and blood products at Memorial Sloan-Kettering Cancer Center. Find out here how to help our patients. ]

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