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Unformatted text preview: an animal, stem cells play a critical role in the
maintenance of most tissues and organs.
The key property of stem cells is that they divide to produce one daughter cell that remains a stem cell and one that divides and
differentiates (Figure 17.17). Because the division of stem cells produces
new stem cells as well as differentiated daughter cells, stem cells are selfrenewing populations that can serve as a source for the production of differentiated cells throughout life. The role of stem cells is particularly evident in
the case of several types of differentiated cells, including blood cells, sperm,
epithelial cells of the skin, and epithelial cells lining the digestive tract—all
of which have short life spans and must be replaced by continual cell proliferation in adult animals. In all of these cases, the fully differentiated cells do
not themselves proliferate; instead, they are continually renewed by the
proliferation of stem cells that then differentiate to maintain a stable number of differentiated cells. Stem cells have also been identified in a variety of
other adult tissues, including skeletal muscle and t...
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