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| {{SI}} | | __NOTOC__ |
| | {{Hematopoeisis}} |
| {{CMG}} | | {{CMG}} |
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| | ==[[Hematopoiesis overview|Overview]]== |
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| | ==[[Hematopoiesis lineages|Lineages]]== |
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| == Overview == | | ==[[Hematopoiesis locations|Locations]]== |
| '''Haematopoiesis''' (from Ancient Greek: ''haima'' blood; ''poiesis'' to make) (or '''hematopoiesis''' in the United States; sometimes also '''haemopoiesis''' or '''hemopoiesis''') is the formation of [[blood]] cellular components. All of the cellular components of the blood are derived from [[haematopoietic stem cell]]s. The term multipotent refers to the ability of a cell to become several different types of cell (but not all types in a germ layer). Multipotent haematopoietic cells can become any type of cell in the blood system. The multipotent cells determine what type of cell to become, or differentiate, in a step-wise fashion.
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| ==Lineages== | | ==[[Hematopoiesis maturation|Maturation]]== |
| All blood cells are divided into three lineages.
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| * [[erythrocyte|Erythroid]] cells are the oxygen carrying [[red blood cells]].
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| * [[Lymphoid]] cells are the cornerstone of the adaptive immune system. They are derived from common lymphoid progenitors. The lymphoid lineage is primarily composed of [[T-cell]]s and [[B-cell]]s. (white blood cells)
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| * [[Myeloid]] cells, which includes [[granulocyte]]s, [[megakaryocyte]]s, and [[macrophage]]s, are derived from common myeloid progenitors, and are involved in such diverse roles as [[innate immunity]], [[adaptive immunity]], and [[blood clotting]].
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| ==Maturation== | | ==Related Chapters== |
| As a stem cell matures it undergoes changes in gene expression (the levels of genes change) that limit the cell types that it can become and move it closer to a specific cell type. These changes can often be tracked by monitoring the presence of proteins on the surface of the cell. Each successive change moves the cell closer to its final choice of cell type and further limits its potential cell type until it is fully differentiated. This process is usually presented as a [[dendrogram]] or decision tree, which starts with a stem cell at the single starting point, and branches for the major lineages that branch into intermediate semi-differentiated cell types, and eventually, to fully differentiated cells.
| | *[[Granulopoiesis]], the hematopoiesis of granulocytes. |
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| ==Locations==
| | {{Immune system}} |
| In developing embryos, blood formation occurs in aggregates of blood cells in the yolk sac, called [[blood islands]]. As development progresses, blood formation occurs in the [[spleen]], [[liver]] and [[lymph node]]s. When [[bone marrow]] develops, it eventually assumes the task of forming most of the blood cells for the entire organism. However, maturation, activation, and some proliferation of lymphoid cells occurs in secondary lymphoid organs (spleen, [[thymus]], and lymph nodes). While most haematopoiesis in adults occurs in the marrow of the long bones such as the [[femur]]s, it also occurs in spongy bone like [[rib]]s and [[sternum]]). In some cases, the liver, thymus, and spleen may resume their haematopoietic function, if necessary (called ''extramedullary haematopoiesis'').
| | {{Hematology}} |
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| In some [[vertebrate]]s, haematopoiesis can occur wherever there is a loose [[stroma]] of connective tissue and slow blood supply, such as the [[gut]], [[spleen]], [[kidney]] or [[ovaries]].
| | [[Category:Blood cells]] |
| | | [[Category:Hematology]] |
| ==Haematopoietic growth factors==
| | [[Category:Histology]] |
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| Red and white blood cell production is regulated with great precision in healthy humans, and the production of granulocytes is rapidly increased during infection. The proliferation and self-renewal of these cells depend on stem cell factor (SCF).
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| Glycoprotein growth factors regulate the proliferation and maturation of the cells that enter the blood from the marrow, and cause cells in one or more committed cell lines to proliferate and mature.
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| Three more factors which stimulate the production of committed stem cells are called '''colony-stimulating factors (CSFs)''' and include '''granulocyte-macrophage CSF (GM-CSF),''' '''granulocyte CSF (G-CSF)''' and '''macrophage CSF (M-CSF)'''.
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| These stimulate a lot of [[granulocyte]] formation. They are active on either [[progenitor cells]] or end product cells.
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| The commitment of all hematopoietic cells to become a certain type of blood cell depends on external signals. [[Erythropoietin]] is required for a myeloid progenitor cell to become an erythrocyte. <ref name=lodish>Molecular cell biology. Lodish, Harvey F. 5. ed. : - New York : W. H. Freeman and Co., 2003, 973 s. b ill. ISBN: 0-7167-4366-3</ref> On the other hand, [[thrombopoietin]] makes myeloid progenitor cells differentiate to [[megakaryocytes]] ([[thrombocyte]]-forming cells).<ref name=lodish/>
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| Examples of cytokines and the blood cells they give rise to, is shown in the picture below.
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| [[Image:Hematopoiesis (human) cytokines.jpg|thumb|left|500px|Diagram including some of the important cytokines that determine which type of blood cell will be created.<ref name=lodish/> | |
| SCF= [[Stem Cell Factor]]
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| Tpo= [[Thrombopoietin]]
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| IL= [[Interleukin]]
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| GM-CSF= [[Granulocyte Macrophage-colony stimulating factor]]
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| Epo= [[Erythropoietin]]
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| M-CSF= [[Macrophage-colony stimulating factor]]
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| G-CSF= [[Granulocyte-colony stimulating factor]]
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| SDF-1= [[Stromal cell-derived factor-1]]
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| FLT-3 ligand= FMS-like tyrosine kinase 3 ligand
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| TNF-a = [[Tumor necrosis factor-alpha]]
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| TGFβ = [[Transforming growth factor]] beta
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| ]]
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| <br clear="left"/>
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| ==References==
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| <references/>
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| == Acknowledgements ==
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| The content on this page was first contributed by: C. Michael Gibson, M.S., M.D.
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| == Suggested Reading and Key General References ==
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| == Suggested Links and Web Resources ==
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| == For Patients ==
| | [[cs:Krvetvorba]] |
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| | [[pl:Hemopoeza]] |
| | [[pt:Hematopoiese]] |
| | [[ru:Гемопоэз]] |
| | [[sv:Hematopoes]] |
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