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Platelets are regulators of hemostasis and thrombosis. Platelets become active in the blood following vascular injury. Vascular injury causes platelets to stick to the cellular matrix that is exposed under the endothelium, form a platelet plug, and then form a thrombus. Platelets are essential in the formation of an occlusive thrombus and are ...
Platelet concentration in the blood (i.e. platelet count), can be measured manually using a hemocytometer, or by placing blood in an automated platelet analyzer using particle counting, such as a Coulter counter or optical methods. [47] Most common blood testing methods include platelet count in their measurements, usually reported as PLT. [48]
Thrombopoietin is a glycoprotein hormone produced by the liver and kidney which regulates the production of platelets. It stimulates the production and differentiation of megakaryocytes, the bone marrow cells that bud off large numbers of platelets. [5] Megakaryocytopoiesis is the cellular development process that leads to platelet production.
In a typical set of rules, a platelet donor must weigh at least 50 kg (110 lb) and have a platelet count of at least 150 x 10 9 /L (150,000 platelets per mm³). [2] One unit has greater than 3×10 11 platelets. Therefore, it takes 2 liters of blood having a platelet count of 150,000/mm³ to produce one unit of platelets.
A normal human platelet count ranges from 150,000 to 450,000 platelets/microliter (μL) of blood. [4] Values outside this range do not necessarily indicate disease. One common definition of thrombocytopenia requiring emergency treatment is a platelet count below 50,000/μL. [ 5 ]
They circulate in the blood of mammals and are involved in hemostasis, leading to the formation of blood clots. Platelets release thread-like fibers to form these clots. The normal range (99% of population analyzed) for platelets is 150,000 to 450,000 per cubic millimeter. [6] If the number of platelets is too low, excessive bleeding can occur.
Exposure of blood to the subendothelial space initiates two processes: changes in platelets, and the exposure of subendothelial platelet tissue factor to coagulation factor VII, which ultimately leads to cross-linked fibrin formation. Platelets immediately form a plug at the site of injury; this is called primary hemostasis.
Aggregation of thrombocytes (platelets). Platelet-rich human blood plasma (left vial) is a turbid liquid. Upon addition of ADP, platelets are activated and start to aggregate, forming white flakes (right vial). Hemostasis occurs when blood is present outside of the body or blood vessels.