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In either scenario, each of these proto-platelet processes can give rise to 2000–5000 new platelets upon breakup. Overall, 2/3 of these newly produced platelets will remain in circulation while 1/3 will be sequestered by the spleen. [medical citation needed] Example of platelets release in mature megakaryocytes.
The megakaryoblast is a platelet precursor that undergoes endomitosis to form megakaryocytes that have 8 to 64 nuclei. Megakaryocytes shed platelets into the bloodstream. β1-tubulin microtubules, which are found in megakaryocytes, facilitate this process of shedding platelets into the bloodstream. [5]
The megakaryocytes release the platelets into the blood stream. [8] The process of platelet production, beginning with the formation of megakaryoblasts, takes about 7 days. Once in the blood stream, platelets last about 8 to 10 days. [8]
Platelets have no cell nucleus; they are fragments of cytoplasm derived from the megakaryocytes [2] of the bone marrow or lung, [3] which then enter the circulation. Platelets are found only in mammals, whereas in other vertebrates (e.g. birds, amphibians), thrombocytes circulate as intact mononuclear cells. [4]: 3
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.
Platelets derived from the abnormal megakaryocytes are activated, which, along with the elevated platelet count, contributes to the likelihood of forming blood clots. [8] The increased possibility of bleeding when the platelet count is over 1 million is due to von Willebrand factor (vWF) sequestration by the increased mass of platelets, leaving ...
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.
The gene SELP encoding P-selectin is located on chromosome 1q21-q24, spans > 50 kb and contains 17 exons in humans. [7] P-selectin is constitutively expressed in megakaryocytes (the precursor of platelets) and endothelial cells. [8]