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Haemopoiesis
Haematopoiesis is the formation of blood cellular components. All cellular blood components are derived from haematopoietic stem cells. In a healthy adult person, approximately 1011–1012 new blood cells are produced daily in order to maintain steady state levels in the peripheral circulatio
Site of haemopoiesis
Fetus: 0–2 months (yolk sac)
2–7 months (liver, spleen)
5–9 months (bone marrow)
Infants: Bone marrow (practically all bones)
Adults: Vertebrae, ribs, sternum, skull, sacrum
and pelvis, proximal ends of femur
Simply a stem cell is a cell that gives rise to many other cells. when it is in the embryo its called Embryonic Stem Cell, and when they are in the bone marrow ready to form Blood Cells they are simply called Haematopoietic Sem Cells or HSCs. This haemopoietic stem cell is rare, perhaps 1 in every 20 million nucleated cells in bone marrow
HSCs are normally found in the bone marrow.
Now lets see why a HSC is so important for.
1. they have self renewal capacity.
2. they can proliferate and differentiate into progenitor cells which in turn are commited to one specific cell line.
sounds too tough?? well it simply means they can easily divide and when they do some of them REMAINS as HSCs for further use.
the divided one then can again multiply many times and form into specific blood cells.
here is a simple diagram of the stem cell making different cells:
_diagram.png)
now, this picture shows all types of haemopoiesis in detail. meaning to say all the cell forming line ups. As the diagram shows, most of the work happens in the bone marrow itself nd some in the blood and very few in the tissues.
[to get a full resolution picture and more image visit this link]
The Bone Marrow
The bone marrow forms a suitable environment for stem cell survival, growth and development. It is composed of:
1.stromal cells and
2.a microvascular network - it provides:
i) nutrition
ii) acts as a transport system to bring new cells into system.
The stromal cells include adipocytes, fibroblasts, endothelial cells and macrophages and they secrete extracellular molecules such as collagen, glycoproteins (fibronectin and thrombospondin)
and glycosaminoglycans (hyaluronic acid and chondroitin derivatives) to form an extracellular
matrix. In addition, stromal cells secrete several growth factors necessary for stem cell survival.
Mesenchymal stem cells are thought to be critical in stromal cell formation.
Haemopoietic growth factors:
Haemopoietic growth factors are hormones that regulate the proliferation & differentiation of haemopoeitic & progenitor cells and function of a mature blood cell. these effects are mediated thorough specific receptor on target cells.
haemopoietic growth factors mainly come from:
1. T-Lymphocyte
2. Monocyte
3. Stromal cells.
Here is a table showing Haemopoietic growth factors and the cells they act on:
Act on stromal cells
IL-1
TNF
Act on pluripotential stem cells
SCF
Flt-L
Act on multipotential progenitor cells
IL-3
GM-CSF
IL-6
G-CSF
Thrombopoietin
Act on committed progenitor cells
G-CSF*
M-CSF
IL-5 (eosinophil-CSF)
Erythropoietin
Thrombopoietin*
This video will help you learn how the real cells look like under microscope. watch with patience....
Haematopoiesis is the formation of blood cellular components. All cellular blood components are derived from haematopoietic stem cells. In a healthy adult person, approximately 1011–1012 new blood cells are produced daily in order to maintain steady state levels in the peripheral circulatio
Site of haemopoiesis
Fetus: 0–2 months (yolk sac)
2–7 months (liver, spleen)
5–9 months (bone marrow)
Infants: Bone marrow (practically all bones)
Adults: Vertebrae, ribs, sternum, skull, sacrum
and pelvis, proximal ends of femur
Haematopoietic stem cells (HSCs)
Before we know about what haematopoetic stem cells are we must first know what a stem cell is..
So, here is a great interactive video for you to learn what a stem cell is..
Simply a stem cell is a cell that gives rise to many other cells. when it is in the embryo its called Embryonic Stem Cell, and when they are in the bone marrow ready to form Blood Cells they are simply called Haematopoietic Sem Cells or HSCs. This haemopoietic stem cell is rare, perhaps 1 in every 20 million nucleated cells in bone marrow
HSCs are normally found in the bone marrow.
Now lets see why a HSC is so important for.
1. they have self renewal capacity.
2. they can proliferate and differentiate into progenitor cells which in turn are commited to one specific cell line.
sounds too tough?? well it simply means they can easily divide and when they do some of them REMAINS as HSCs for further use.
the divided one then can again multiply many times and form into specific blood cells.
here is a simple diagram of the stem cell making different cells:
_diagram.png)
now, this picture shows all types of haemopoiesis in detail. meaning to say all the cell forming line ups. As the diagram shows, most of the work happens in the bone marrow itself nd some in the blood and very few in the tissues.
[to get a full resolution picture and more image visit this link]
The Bone Marrow
The bone marrow forms a suitable environment for stem cell survival, growth and development. It is composed of:
1.stromal cells and
2.a microvascular network - it provides:
i) nutrition
ii) acts as a transport system to bring new cells into system.
The stromal cells include adipocytes, fibroblasts, endothelial cells and macrophages and they secrete extracellular molecules such as collagen, glycoproteins (fibronectin and thrombospondin)
and glycosaminoglycans (hyaluronic acid and chondroitin derivatives) to form an extracellular
matrix. In addition, stromal cells secrete several growth factors necessary for stem cell survival.
Mesenchymal stem cells are thought to be critical in stromal cell formation.
Haemopoietic growth factors:
Haemopoietic growth factors are hormones that regulate the proliferation & differentiation of haemopoeitic & progenitor cells and function of a mature blood cell. these effects are mediated thorough specific receptor on target cells.
haemopoietic growth factors mainly come from:
1. T-Lymphocyte
2. Monocyte
3. Stromal cells.
Here is a table showing Haemopoietic growth factors and the cells they act on:
Act on stromal cells
IL-1
TNF
Act on pluripotential stem cells
SCF
Flt-L
Act on multipotential progenitor cells
IL-3
GM-CSF
IL-6
G-CSF
Thrombopoietin
Act on committed progenitor cells
G-CSF*
M-CSF
IL-5 (eosinophil-CSF)
Erythropoietin
Thrombopoietin*
This video will help you learn how the real cells look like under microscope. watch with patience....
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