|MadSci Network: General Biology|
The cells in our body may be broadly divided by their divisional activities. Nature has cleverly placed the stem cells at the locations where they are really required. For instance, there are haematopoietic stem cells in bone marrow, stem cells in the basal layer of skin and the lining layer of lumen, spermatogonial cells in man's reproductive system and many more such places which require a constant supply of functional cells. Usually, the functional cells, that is, those that are responsible for functions of our body, are either slow dividing or not dividing at all. However, they are exposed to constant wear out kinds of situations. Hence, they need to be constantly replaced. Stem cells do that job very effectively. If by some method the cell division is stopped, it leads to cut off of the supply of functional cells. For example, if bone marrow is depleted, there will be a drastic reduction (within 60 days) in the lymphocyte counts as well as the level of other blood cells leading to infection and other blood related disorders. If crypt cells in the intestine are damaged (say by very high doses of radiation), it leads to gastointestinal damage and can lead to lethal effects due to ion imbalance in the intestine. Comparatively stable cells such as nerve cells are least affected against environmental causes because the wear and tear of these cells are not much. Nevertheless, when all stem cell division is affected, nerve cells will eventually also be affected. When the supply line of functional cells is cut off, it leads to fibrosis of tissue leading to either impaired functionality of the tissue or its failure.
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