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Encyclopedia > Megakaryocyte

The megakaryocyte is a bone marrow cell responsible for the production of blood platelets when its cytoplasm becomes fragmented. These fragments are blood platelets. Megakaryocytes account for less than 1% of bone marrow cells but can be 10 to 15 times larger than a typical red blood cell.(Compare to other cells) DNA synthesis is occuring in the nucleus during thrombopoiesis (stimulated by thrombopoietin) without cytokenesis, aka endoreduplication. Therefore, the nucleus of the megakaryocyte can become very large and lobulated, which, under a light microscope, can give the false impression that there are several nuclei. In some cases, the nucleus may contain up o 64N DNA. Grays Anatomy illustration of cells in bone marrow. ... Cells in culture, stained for keratin (red) and DNA (green). ... A 250 ml bag of newly collected platelets. ...


Platelets are held within demarcation channels, internal membranes within the cytoplasm of megakaryocytes. Megakaryocytes release their platelets in one of two ways. The cell may release its platelets by rupturing and releasing its contents all at once in the marrow. Alternatively, the cell may form platelet ribbons into blood vessels. The ribbons are formed via psuedopodia and they are able to continuously emit platelets into circulation. 2/3 of these platelets will remain in circulation while 1/3 will be sequestered by the spleen.


Megakaryocyte function is determined by a large number of cytokines, including thrombopoietin. Cytokines is a group of proteinaceous signalling compounds that like hormones and neurotransmitters are used extensively for inter-cell communication. ... Thrombopoietin is the recently discovered (1994) glycoprotein hormone that regulates the production of platelets. ...


The developmental stages of the megakaryocyte is: CFU-Me (pluripotential hemopoietic stem cell or hemocytoblast) -> megakaryoblast -> promegakaryocyte -> megakaryocyte. Sketch of bone marrow and its cells Pluripotential hemopoietic stem cells or pluripotential hematopoietic stem cells (PHSCs) are stem cells found in the bone marrow. ... A megakaryoblast is a precursor cell to a promegakaryocyte, which in turn becomes a megakaryocyte. ...

Blood - Blood plasma - edit
Pluripotential hemopoietic stem cells | Red blood cells (ReticulocyteNormoblast) | White blood cells
Lymphocytes (Lymphoblast)
T cells (CytotoxicHelperRegulatory T cellsNatural Killer T cells) | B cells (Plasma cells & Memory B cells) | Natural killer cells
Myelocytes (Myeloblast)
Granulocytes (NeutrophilEosinophilBasophil) | Mast cell precursors | Monocytes (HistiocyteMacrophagesDendritic cellsLangerhans cells, MicrogliaKupffer cellsOsteoclasts) | Megakaryoblast | Megakaryocyte | Platelets

  Results from FactBites:
 
Megakaryocyte - Encyclopedia, History, Geography and Biography (168 words)
Megakaryocytes account for less than 1% of bone marrow cells but can be 10 to 15 times larger than a typical red blood cell.(Compare to other cells) The nucleus of the megakaryocyte is very large and lobulated, which, under a light microscope, can give the false impression that there are several nuclei.
Megakaryocyte function is determined by a large number of cytokines, including thrombopoietin.
The developmental stages of the megakaryocyte is:CFU-Me (pluripotential hemopoietic stem cell or hemocytoblast) -> megakaryoblast -> promegakaryocyte -> megakaryocyte.
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