| MadSci Network: Anatomy |
Your question is a very good one, but unfortunately I don't really know the answer. Every organ in the human body is made up of cells, and in general most cells have the capacity to divide if stimulated to do so by certain chemical factors. Some organs are made up of cells which divide very frequently, for example the intestines, where the epithelial cells along the insides of these organs are basically constantly being replaced by fresh cells. This sort of rapid cell division is also always going on the bone marrow, the site where cells divide and give rise to all of the different types of cells circulating in the blood. Another site of rapid cell division is the deep layers of the skin, to supply fresh cells to replace the outer layers of dead skin which are constantly being sloughed off. Some organs are likely made up of cells which divide only very slowly to replace old, dying cells. Some cells in some organs are most likely very long lived (as are neurons within the brain), although the exact rate of turnover and replacement is likely not known for certain. If you'd like to know more about the process of cell division in general, a good link that I found is: http://mindquest.net/biology/cell-biology/monographs/cell-replication.html I hope this helps.
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