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[[Image:Thrombopoiesis_pathway.jpg|right|thumb|125px|'''Thrombopoiesis Pathway''']]
[[Image:Thrombopoiesis_pathway.jpg|right|thumb|125px|'''Thrombopoiesis Pathway''']]
===Stem Cell===
===Stem Cell===
As with [[Erythrocytes|erythrocytes]], [[Thrombocytes|thrombocytes]] are derived from multipotential myeloid stem cells ([[Haematopoiesis - Overview#Colony Forming Units|CFU-GEMM]]). In the [[Bone Marrow - Anatomy & Physiology|bone marrow]] CFU-GEMM cells differentiate into the megakaryocyte precursor cell the megakaryocyte CFU ([[Haematopoiesis - Overview#Colony Forming Units|CFU-Meg]]), under the influence of CFU-CSF and IL-3. Unlike other blood cells which undergo mitosis in the first few developmental stages, once the [[Haematopoiesis - Overview#Colony Forming Units|CFU-GEMM]] has differentiated into the [[Haematopoiesis - Overview#Colony Forming Units|CFU-Meg]] there is no further mitosis. The [[Haematopoiesis - Overview#Colony Forming Units|CFU-Meg]] then differentiates into the megakaryoblast.
As with [[Erythrocytes|erythrocytes]], [[Thrombocytes|thrombocytes]] are derived from multipotential myeloid stem cells ([[Haematopoiesis - Overview#Colony Forming Units|CFU-GEMM]]). In the [[Bone Marrow - Anatomy & Physiology|bone marrow]] CFU-GEMM cells differentiate into the megakaryocyte precursor cell the megakaryocyte CFU ([[Haematopoiesis - Overview#Colony Forming Units|CFU-Meg]]), under the influence of [[Cytokines|cytokines]] CFU-CSF and IL-3. Unlike other blood cells which undergo mitosis in the first few developmental stages, once the CFU-GEMM has differentiated into the CFU-Meg there is no further mitosis. The CFU-Meg then develops into the megakaryoblast.
===Megakaryoblast===
===Megakaryoblast===
Cell is slightly basophilic, around 30µm and has a round nucleus that is non-lobed.
Cell is slightly basophilic, around 30µm and has a round nucleus that is non-lobed.
===Megakaryocyte===
===Megakaryocyte===
Cell is around 50-70µm and responds to thrombopoietin (TPO) and undergoes [[endomitosis]] until the cell reaches around 64n. The size of the cell's cytoplasm and nucleus increases with the increase in the cell's chromosome number.
====Thrombopoietin ====
====Thrombopoietin ====
Similarly to [[Erythropoiesis#Regulation|erythropoietin]], thrombopoietin (TPO) regulates the production of thrombocytes by stimulating [[Haematopoiesis - Overview#Colony Forming Units|CFU-Meg]] to mature into megakaryocytes. TPO is mainly produced in the liver and acts via a negative feedback system. It binds to TPO receptors on both the megakaryocytes and platelets. Thus if these are in high concentrations in the blood plasma then the level of TPO is kept low, reducing the maturation of [[Haematopoiesis - Overview#Colony Forming Units|CFU-Meg]] and production of thrombocytes is reduced.
Similarly to [[Erythropoiesis#Regulation|erythropoietin]], thrombopoietin (TPO) regulates the production of thrombocytes by stimulating CFU-Meg to mature into megakaryocytes. TPO is mainly produced in the liver and is regulated by a negative feedback system. It binds to TPO receptors on both the megakaryocytes and platelets; if these are in high concentrations in the blood plasma then the level of TPO is kept low, reducing the maturation of CFU-Meg and thrombocyte production.
==Thrombocyte formation==
==Thrombocyte formation==