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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 ...
[67] [68] Platelets were described in the early 19th century, and in the 1880s several investigators linked the purpura with abnormalities in the platelet count. [67] [69] The first report of a successful therapy for ITP was in 1916, when a young Polish medical student, Paul Kaznelson, described a female patient's response to a splenectomy. [67]
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 ]
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]
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.
A pseudothrombocytopenia false-positive result may occur when automated platelet counting devices are used. As a means of double checking the results, the patient's blood sample is often examined under a microscope. If the clumping is visible and the number of platelets appears normal, pseudothrombocytopenia may be concluded.
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.
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.