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#REDIRECT [[Haematopoiesis and Blood Cells - WikiBlood]]
Also referred to as haemopoiesis or hemopoiesis and is the process of blood cell formation. All blood cells are derived from the initial pluripotent stem cell (PPSC) which gives rise to colony forming units (CFU). These CFU's further differentiate to give rise to the various blood cells found.
==Development==
{| align="right"
|<gallery>
Image:LH_Variety_blood_cells_Histology.jpg|<center><p>'''Blood cells'''</p><sup>©RVC 2008</sup></center>
Image:LH_Avian_Variety_blood_cells_Histology.jpg|<center><p>'''Avian Blood cells'''</p><sup>©RVC 2008</sup></center></gallery>
|}
<p>PPSC’s initially divide and differentiate into multipotential haematopoietic stem cells. Multipotential haematopoietic stem cells only have the ability to mature into a single cell lineage, either myeloid progenitors (granulocytes, erythroblasts, [[Macrophages|macrophages]] and megakaryocytes) or lymphoid progenitors. The development of blood cells from the multipotential haematopoietic stem cell into the final mature cell is categorised into:
* The formation of [[Erythrocytes|erythrocytes]] ([[Erythropoiesis|Erythropoiesis]])
* The formation of white blood cells ([[Leukopoiesis|Leukopoiesis]])
* The formation of platelets ([[Thrombopoiesis|Thrombopoiesis]])</p>
<p>White blood cells are further classified by the lineage of the white blood cell being formed. Thus the development of white blood cells is further categorised into:
* Formation of [[Neutrophils|neutrophils]], [[Eosinophils|eosinophils]] and [[Basophils|basophils]] ([[Leukopoiesis#Granulopoiesis|Granulopoiesis]])
* Formation of [[Lymphocytes#B cells|B cells]] and [[Lymphocytes#Helper CD4+|T cells]] ([[Leukopoiesis#Lymphopoiesis|Lymphopoiesis]])
* Formation of [[Monocytes|monocytes]] and [[Macrophages|macrophages]] ([[Leukopoiesis#Monocyte Development|See here]])</p>
==Stages==
===Fetal===
====Yolk Sac Phase====
<p>Blood islands from the mesoderm form in the yolk sac early in gestation. They provide primitive erythrocytes to support the developing embryo. These blood islands also give rise to the haematopoietic stem cells.</p>
<p>Haematopoiesis also occurs within the embryo at a region called the aorta-gonad-mesonephros region (AGM).</p>
====Hepatic Phase====
<p>''Back to [[Primary Lymphoid Tissue - Anatomy & Physiology|Primary Lymphoid Tissue]]</p>
<p>As embryological development continues haematopoiesis shifts from the yolk sac and AGM to the foetal [[Liver - Anatomy & Physiology|liver]] (and [[Spleen - Anatomy & Physiology|spleen]]). Haematopoietic areas form in the [[Liver - Anatomy & Physiology|liver]] which become the main haematopoietic organ in the body. [[Erythropoiesis|Erythropoiesis]] is the dominant process but some [[Leukopoiesis|leukopoiesis]] occurs so the foetal [[Liver - Anatomy & Physiology|liver]] can be considered a [[Primary Lymphoid Tissue - Anatomy & Physiology| primary lymphoid organ]].</p>
<p>For pathology of the foetal liver see [[Foetal Liver - Pathology#pathology|here]].</p>
====Bone marrow phase====
Haematopoiesis starts to occur in the [[Bone Marrow - Anatomy & Physiology|bone marrow]] later in gestation, and the [[Spleen - Anatomy & Physiology|spleen]] becomes the main [[Erythrocytes|erythrocyte]] producing organ during the transitional phase from [[Liver - Anatomy & Physiology|liver]] to [[Bone Marrow - Anatomy & Physiology|bone marrow]].
===Adult===
Haematopoiesis occurs in [[Bone Marrow - Anatomy & Physiology|bone marrow]] and maturation of lymphocytes in lymphoid tissues. In the bone marrow the haematopoietic cells are supported by stromal cells which generate the correct environments to cause the growth and development of the different blood cell types.
==Lineages==
The lineage of a blood cell is based on the multipotential stem cell that the cell is derived from.
* Lymphoid cells are derived from the multipotential lymphoid stem cells
* Cells derived from the multipotential myeloid stem cells are either:
** Erythroid lineage (forming erythrocytes) or
** Myeloid lineage (forming [[Neutrophils|neutrophils]], [[Monocytes|monocytes]], [[Macrophages|macrophages]], [[Eosinophils|eosinophils]], [[Basophils|basophils]] and [[Thrombocytes|platelets]])
===Colony Forming Units===
{|
|CFU-L
|(multipotential lymphoid stem cell forming [[Lymphocytes#T cells|T cells]], [[Lymphocytes#B cells|B cells]] and [[Lymphocytes#NK cells|NK cells]])
|-
|CFU-GEMM
|(multipotential myeloid stem cell, forming granulocytes, erythroblasts, macrophages and megakaryocytes)
|-
|CFU-E
|(forming [[Erythrocytes|erythrocytes]])
|-
|CFU-GM
|(forming [[Neutrophils|neutrophils]] and [[Monocytes|monocytes]]/[[Macrophages|macrophages]])
|-
|CFU-Eo
|(forming [[Eosinophils|eosinophils]])
|-
|CFU-Ba
|(forming [[Basophils|basophils]])
|-
|CFU-Mast
|(forming [[Mast Cells|mast cells]])
|-
|CFU-Meg
|(forming [[Thrombocytes|platelets]])
|}
====CFU Development====
{| cellpadding="5" cellspacing="1" border="1"
|colspan="10" align="center"|Pluripotential Stem Cell ('''PPSC''')
|-align="center"
|colspan="7" style="background-color:#ffffcc"|Multipotential myeloid stem cell ('''CFU-GEMM''')
|colspan="3" style="background-color:#e6e6fa"|Multipotential lymphoid stem cell ('''CFU-L''')
|-align="center"
|rowspan="2" style="background-color:#ffffcc"|<p>Erythroid CFU</p>('''CFU-E''')
|rowspan="2" style="background-color:#ffffcc"|<p>Megakaryocyte CFU</p>('''CFU-Meg''')
|colspan="2" style="background-color:#ffffcc"|<p>Granulocyte CFU</p>('''CFU-GM''')
|rowspan="2" style="background-color:#ffffcc"|<p>Basophil CFU</p>('''CFU-Ba''')
|rowspan="2" style="background-color:#ffffcc"|<p>Eosinophil CFU</p>('''CFU-Eo''')
|rowspan="2" style="background-color:#ffffcc"|<p>Mast Cell CFU</p>('''CFU-Mast''')
|rowspan="2" colspan="3" style="background-color:#e6e6fa"|-
|-align="center"
|style="background-color:#ffffcc"|<p>Neutrophil CFU</p>('''CFU-G''')
|style="background-color:#ffffcc"|<p>Monocyte CFU</p>('''CFU-M''')
|-align="center"
|style="background-color:#ffffcc"|[[Erythrocytes|'''Erythrocyte''']]
|style="background-color:#ffffcc"|[[Thrombocytes|'''Megakaryocyte''']]
|style="background-color:#ffffcc"|[[Neutrophils|'''Neutrophil''']]
|style="background-color:#ffffcc"|[[Monocytes|'''Monocyte''']]
|style="background-color:#ffffcc"|[[Basophils|'''Basophil''']]
|style="background-color:#ffffcc"|[[Eosinophils|'''Eosinophil''']]
|style="background-color:#ffffcc"|[[Mast Cells|'''Mast Cell''']]
|colspan="3" style="background-color:#e6e6fa"|'''[[Lymphocytes#T cell|T cell]]''', '''[[Lymphocytes#B cells|B cell]]''' & '''[[Lymphocytes#NK cells|NK cell]]'''
|}
==Links==
[[Lymphoreticular System - Anatomy & Physiology|Lymphoreticular System]]