This is vital to maintain, increase or reduce stem cell number. Each stem cell division makes two new cells and the fate of those cells is central to what happens. It is really important that the stem cell system is controlled. Self-renewal is vital to ensure we do not "run out of stem cells" as we get older but must be tightly controlled to ensure we do not end up with too many or too few stem cells.
Differentiation is also vital since that is what makes mature cells - again the right number of cells must enter differentiation to make mature blood cells The Self Renewal Choice What happens if stem cell division has different fates:.
If each division produces one identical daughter cell self-renewal then number of stem cells is maintained. Fewer self-renewal at lower rates, or higher rates has a massive impact even over a limited number of divisions. This mechanism allows stem cell number to be adapted to need but emphasises the importance of control. The differentiation choice is also important for flexibility, where the stem cell becomes committed to a particular lineage.
Controlling which lineage, it takes allows the selective expansion of one or more mature cell types. How Stem Cells avoid Cancer The lower the number of stem cells the lower the risk of a mutation that might cause cancer. So once haematopoietic stem cells become committed to development.
Its committed daughter cells then make up to 19 cycles of division before a mature cell is made. This gives up to , mature cells from each stem cell, however the stem cell itself needs to divide only once so relatively few stem cells and stem cell divisions are needed to support the body's needs.
The stem cell niche is also an important control - stem cells find it difficult to survive outside of this particular environment - so if a cell does lose control of self-replication it will still find it difficult to survive as it overcrowds its niche. The stem cell depends greatly on the cells and proteins around it - this is known as the "stem cell niche". The elements of the niche can control the stem cell function and stem cells cannot survive well outside this niche - this prevents an excessive expansion of numbers.
These lineages committed cells can no longer self-renew, but can greatly expand their number.
The process therefore is tightly controlled. The Proliferating and Differentiating Pool The committed precursor cells are not simply the "in-between cells" that link stem cells to mature cells - their behaviour is vital to the control of haematopoiesis.follow site
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The number of cells potentially produced here is huge - a single stem cell entering the committed precursor pool can make up to around 20 divisions each yielding two daughter cells. This produces a lot of mature cells: 2, 4, 8, 16, 32, 64, etc as divisions continue and each stem cell can therefore produce as many as , mature cells.
This is the stage where number is controlled. Initially cells are highly proliferative, but as the process develops they acquire more functional characteristics and no longer proliferate. When we look at blood cells in bone marrow we see the appearances change from initial highly proliferative appearances to later cells that resemble mature cells and act very similarly to mature cells with fewer numbers of division.
Death is a really important mechanism to control the numbers.
This shows in a diagram how a single stem cell makes many mature cells of red cell, white cell or platelet types, but also many dead cells. By varying death in a particular lineage, fine control over red cells, white cells or platelets can be achieved. Technical settings.
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