What is Platelet?
[[File:Platelet_blood_bag.jpg|thumb|A 250 [[millilitre|ml]] bag of newly collected '''platelets'''.]] A '''platelet''' is a cell fragment that circulates in the [[blood]]. Platelets are involved in [[hemostasis]] through the making of [[blood clot]]s. A low platelet count (number of platelets in the blood) can cause a person to [[bleeding|bleed]] without their blood [[clot]]ting (making scabs). A high platelet count can increase the risk of [[thrombosis]] (blood clots inside [[blood vessel]]s), which stops blood from flowing properly. == Anatomy == Platelets do not have a [[cell nucleus]]. They are [[disc]]-shaped, and are 1.5 to 3 [[micrometer]]s in [[diameter]]. The body does not have a lot of platelets, so they can all be used up quickly. They contain [[RNA]], a [[canaliculus|canalicular]] system, and several different types of granules; [[lysosome]]s (containing [[acid hydrolases]]), [[dense bodies]] (containing [[adenosine diphosphate|ADP]], [[adenosine triphosphate|ATP]] [[serotonin]] and [[calcium]]) and [[alpha granules]] (containing [[fibrinogen]], [[factor V]], [[vitronectin]], [[thrombospondin]] and [[von Willebrand factor]]), the contents of which are released when the platelet is activated. {{biology-stub}} [[Category:Blood]]