Difference between revisions of "Haematopoiesis - Overview"
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| − | [[Image:LH_Variety_blood_cells_Histology.jpg|right|thumb| | + | [[Image:LH_Variety_blood_cells_Histology.jpg|right|thumb|200px|<p>'''Blood cells'''</p><sup>©RVC 2008</sup>]] |
==Introduction== | ==Introduction== | ||
| − | + | 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 circultaion into tissues, such as mast cells and macrophages. | |
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| − | 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 | ||
==Development== | ==Development== | ||
| − | [[Image:LH_Avian_Variety_blood_cells_Histology.jpg|right|thumb| | + | [[Image:LH_Avian_Variety_blood_cells_Histology.jpg|right|thumb|200px<p>'''Avian Blood cells'''</p><sup>©RVC 2008</sup>]] |
| − | |||
| − | The development of blood cells from the haematopoietic stem cell into the final mature cell is categorised into: | + | <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 | + | * 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]]) | + | * 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, eosinophils and basophils ([[Leukopoiesis#Granulopoiesis|Granulopoiesis]]) | + | * Formation of [[Neutrophils|neutrophils]], [[Eosinophils|eosinophils]] and [[Basophils|basophils]] ([[Leukopoiesis#Granulopoiesis|Granulopoiesis]]) |
| − | * Formation of B cells and T cells ([[Leukopoiesis#Lymphopoiesis|Lymphopoiesis]]) | + | * 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==== | ====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> | ||
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====Hepatic Phase==== | ====Hepatic Phase==== | ||
| − | + | Occurs within [[Foetal Liver]] | |
====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 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 | + | 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== | ==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 | + | * Lymphoid cells 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 | ||
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{| | {| | ||
|CFU-L | |CFU-L | ||
| − | |(multipotential lymphoid stem cell forming [[T cells]], [[B cells]] and [[ | + | |(multipotential lymphoid stem cell forming [[Lymphocytes#T cells|T cells]], [[Lymphocytes#B cells|B cells]] and [[Lymphocytes#NK cells|NK cells]]) |
|- | |- | ||
|CFU-GEMM | |CFU-GEMM | ||
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|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"|'''[[T cells|T cell]]''', '''[[B cells|B cell]]''' & '''[[ | + | |colspan="3" style="background-color:#e6e6fa"|'''[[Lymphocytes#T cells|T cell]]''', '''[[Lymphocytes#B cells|B cell]]''' & '''[[Lymphocytes#NK cells|NK cell]]''' |
|} | |} | ||
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[[Category:Haematopoiesis|A]] | [[Category:Haematopoiesis|A]] | ||
Revision as of 09:13, 28 September 2010
Introduction
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 circultaion into tissues, such as mast cells and macrophages.
Development
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 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 (Erythropoiesis)
- The formation of white blood cells (Leukopoiesis)
- The formation of platelets (Thrombopoiesis)
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, eosinophils and basophils (Granulopoiesis)
- Formation of B cells and T cells (Lymphopoiesis)
- Formation of monocytes and macrophages (See here)
Stages
Fetal
Yolk Sac Phase
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.
Haematopoiesis also occurs within the embryo at a region called the aorta-gonad-mesonephros region (AGM).
Hepatic Phase
Occurs within Foetal Liver
Bone marrow phase
Haematopoiesis starts to occur in the bone marrow later in gestation, and the spleen becomes the main erythrocyte producing organ during the transitional phase from liver to bone marrow.
Adult
Haematopoiesis occurs in 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, monocytes, macrophages, eosinophils, basophils and platelets)
Colony Forming Units
| CFU-L | (multipotential lymphoid stem cell forming T cells, B cells and NK cells) |
| CFU-GEMM | (multipotential myeloid stem cell, forming granulocytes, erythroblasts, macrophages and megakaryocytes) |
| CFU-E | (forming erythrocytes) |
| CFU-GM | (forming neutrophils and monocytes/macrophages) |
| CFU-Eo | (forming eosinophils) |
| CFU-Ba | (forming basophils) |
| CFU-Mast | (forming mast cells) |
| CFU-Meg | (forming platelets) |
CFU Development
| Pluripotential Stem Cell (PPSC) | |||||||||
| Multipotential myeloid stem cell (CFU-GEMM) | Multipotential lymphoid stem cell (CFU-L) | ||||||||
Erythroid CFU (CFU-E) |
Megakaryocyte CFU (CFU-Meg) |
Granulocyte CFU (CFU-GM) |
Basophil CFU (CFU-Ba) |
Eosinophil CFU (CFU-Eo) |
Mast Cell CFU (CFU-Mast) |
- | |||
Neutrophil CFU (CFU-G) |
Monocyte CFU (CFU-M) | ||||||||
| Erythrocyte | Megakaryocyte | Neutrophil | Monocyte | Basophil | Eosinophil | Mast Cell | T cell, B cell & NK cell | ||