Changes

==Introduction==

==Introduction==

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.

 

 

Haematopoiesis is also known as haemopoiesis or hemopoiesis and describes 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 (CFUs). These CFUs further differentiate to give rise to their final stage of development where they become the various forms of blood cells or those cells which migrate from the circulation into tissues, such as mast cells and macrophages.

==Development==

==Development==

[[Image:LH_Avian_Variety_blood_cells_Histology.jpg|right|thumb|210px<p>'''Avian Blood cells'''</p>^{©RVC 2008}]]

PPSC’s initially divide and differentiate into multipotential haematopoietic stem cells of one of two lineages: myeloid progenitors (granulocytes, erythroblasts, [[Macrophages|macrophages]] and megakaryocytes) or lymphoid progenitors (B lymphocytes, T lymphocytes and NK cells).

Image:LH_Variety_blood_cells_Histology.jpg|<center><p>'''Blood cells'''</p>^{©RVC 2008}</center>

 

Image:LH_Avian_Variety_blood_cells_Histology.jpg|<center><p>'''Avian Blood cells'''</p>^{©RVC 2008}</center></gallery>

The development of blood cells from the haematopoietic stem cell into the final mature cell is categorised into:  

* The formation of red blood cells ([[Erythropoiesis|Erythropoiesis]])

<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 white blood cells ([[Leukopoiesis|Leukopoiesis]])

* The formation of platelets ([[Thrombopoiesis|Thrombopoiesis]])</p>

* The formation of platelets ([[Thrombopoiesis|Thrombopoiesis]])

<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:

Leukopoiesis is further classified by the lineage of the white blood cell being formed, namely:  

* Formation of [[Neutrophils|neutrophils]], [[Eosinophils|eosinophils]] and [[Basophils|basophils]] ([[Leukopoiesis#Granulopoiesis|Granulopoiesis]])

* Formation of neutrophils, eosinophils and basophils ([[Leukopoiesis#Granulopoiesis|Granulopoiesis]])

* Formation of [[Lymphocytes#B cells|B cells]] and [[Lymphocytes#Helper CD4+|T cells]] ([[Leukopoiesis#Lymphopoiesis|Lymphopoiesis]])

* Formation of B cells and T cells ([[Leukopoiesis#Lymphopoiesis|Lymphopoiesis]])

* Formation of [[Monocytes|monocytes]] and [[Macrophages|macrophages]] ([[Leukopoiesis#Monocyte Development|See here]])</p>

[[File:NWL 2016 Labfacts inners A4 PRESS optimize(90).jpg|thumb|Bone Marrow Histology|link=Special:FilePath/NWL_2016_Labfacts_inners_A4_PRESS_optimize(90).jpg]]

==Stages==

==Foetal Haematopoiesis==

===Fetal===

====Yolk Sac Phase====

====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>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>

====Hepatic Phase====

====Hepatic Phase====

As embryological development continues haematopoiesis shifts from the yolk sac and AGM to the foetal 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 predominant process but some [[Leukopoiesis|leukopoiesis]] occurs so the foetal liver can be considered a [[:Category:Primary Lymphoid Tissue| primary lymphoid organ]].

<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>

====Bone marrow phase====

====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]].

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 in Adults==

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.

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 environment to induce the growth and development of the different blood cell types.

==Lineages==

==Lineages==

The lineage of a blood cell is based on the multipotential stem cell that the cell is derived from.  

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

* Lymphoid cells (lymphocytes) are derived from the multipotential lymphoid stem cells

* Cells derived from the multipotential myeloid stem cells are either:

* Cells derived from the multipotential myeloid stem cells are either:

** Erythroid lineage (forming erythrocytes) or

** Erythroid lineage (forming erythrocytes) or

{|

{|

|CFU-L  

|CFU-L  

|(multipotential lymphoid stem cell forming [[Lymphocytes#T cells|T cells]], [[Lymphocytes#B cells|B cells]] and [[Lymphocytes#NK cells|NK cells]])

|(multipotential lymphoid stem cell forming [[T cells]], [[B cells]] and [[Natural Killer cells|NK cells]])

|-

|-

|CFU-GEMM

|CFU-GEMM

|style="background-color:#ffffcc"|[[Eosinophils|'''Eosinophil''']]

|style="background-color:#ffffcc"|[[Eosinophils|'''Eosinophil''']]

|style="background-color:#ffffcc"|[[Mast Cells|'''Mast Cell''']]

|style="background-color:#ffffcc"|[[Mast Cells|'''Mast Cell''']]

|colspan="3" style="background-color:#e6e6fa"|'''[[Lymphocytes#T cells|T cell]]''', '''[[Lymphocytes#B cells|B cell]]''' & '''[[Lymphocytes#NK cells|NK cell]]'''

|colspan="3" style="background-color:#e6e6fa"|'''[[T cells|T cell]]''', '''[[B cells|B cell]]''' & '''[[Natural Killer cells|NK cell]]'''

|}

|}

[[Category:Haematopoiesis|A]]

[[Category:Haematopoiesis|A]]