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Created page with 'Thrombopoiesis is the process of formation of thrombocytes (platelets). ==Stages== [[Image:Thrombopoiesis_pathway.jpg|right|thumb|100px|'''Thro…'
Thrombopoiesis is the process of formation of [[Thrombocytes|thrombocytes]] ([[Thrombocytes|platelets]]).
==Stages==
[[Image:Thrombopoiesis_pathway.jpg|right|thumb|100px|'''Thrombopoiesis Pathway''']]
===Stem Cell===
As with [[Erythrocytes|erythrocytes]], [[Thrombocytes|thrombocytes]] are derived from multipotential myeloid stem cells ([[Overview of Haematopoiesis - WikiBlood#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 ([[Overview of Haematopoiesis - WikiBlood#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 [[Overview of Haematopoiesis - WikiBlood#Colony Forming Units|CFU-GEMM]] has differentiated into the [[Overview of Haematopoiesis - WikiBlood#Colony Forming Units|CFU-Meg]] there is no further mitosis. The [[Overview of Haematopoiesis - WikiBlood#Colony Forming Units|CFU-Meg]] then differentiates into the megakaryoblast.
===Megakaryoblast===
Cell is slightly basophilic, around 30µm and has a round nucleus that is non-lobed.
===Promegakaryoblast===
Cell is around 45µm with a larger cytoplasm and nucleus.
===Megakaryocyte===
Cells 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 number of chromosomes.
====Thrombopoietin ====
Similarly to [[Erythropoiesis - WikiBlood#Regulation|erythropoietin]], thrombopoietin (TPO) regulates the production of thrombocytes by stimulating [[Overview of Haematopoiesis - WikiBlood#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 [[Overview of Haematopoiesis - WikiBlood#Colony Forming Units|CFU-Meg]] and production of thrombocytes is reduced.
==Thrombocyte formation==
The cell is now a giant cell referred to as the megakaryocyte. Pieces of its cytoplasm and cell membrane bud off to form the [[Thrombocytes|thrombocytes]]. One megakaryocyte can produce up to 6000 thrombocytes.
[[Image:LH Megakaryocytes Histology.jpg|left|thumb|150px|<p>'''Megakaryocytes'''</p><sup>©RVC 2008</sup>]]
<Br clear="left">
==Links==
[[Lymphoreticular System - Anatomy & Physiology|Lymphoreticular System]]
[[Thrombocytes|Thrombocytes]]
==Stages==
[[Image:Thrombopoiesis_pathway.jpg|right|thumb|100px|'''Thrombopoiesis Pathway''']]
===Stem Cell===
As with [[Erythrocytes|erythrocytes]], [[Thrombocytes|thrombocytes]] are derived from multipotential myeloid stem cells ([[Overview of Haematopoiesis - WikiBlood#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 ([[Overview of Haematopoiesis - WikiBlood#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 [[Overview of Haematopoiesis - WikiBlood#Colony Forming Units|CFU-GEMM]] has differentiated into the [[Overview of Haematopoiesis - WikiBlood#Colony Forming Units|CFU-Meg]] there is no further mitosis. The [[Overview of Haematopoiesis - WikiBlood#Colony Forming Units|CFU-Meg]] then differentiates into the megakaryoblast.
===Megakaryoblast===
Cell is slightly basophilic, around 30µm and has a round nucleus that is non-lobed.
===Promegakaryoblast===
Cell is around 45µm with a larger cytoplasm and nucleus.
===Megakaryocyte===
Cells 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 number of chromosomes.
====Thrombopoietin ====
Similarly to [[Erythropoiesis - WikiBlood#Regulation|erythropoietin]], thrombopoietin (TPO) regulates the production of thrombocytes by stimulating [[Overview of Haematopoiesis - WikiBlood#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 [[Overview of Haematopoiesis - WikiBlood#Colony Forming Units|CFU-Meg]] and production of thrombocytes is reduced.
==Thrombocyte formation==
The cell is now a giant cell referred to as the megakaryocyte. Pieces of its cytoplasm and cell membrane bud off to form the [[Thrombocytes|thrombocytes]]. One megakaryocyte can produce up to 6000 thrombocytes.
[[Image:LH Megakaryocytes Histology.jpg|left|thumb|150px|<p>'''Megakaryocytes'''</p><sup>©RVC 2008</sup>]]
<Br clear="left">
==Links==
[[Lymphoreticular System - Anatomy & Physiology|Lymphoreticular System]]
[[Thrombocytes|Thrombocytes]]