2009 sinauer associates inc uncorrected page proofs

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Unformatted text preview: em cells Sebaceous gland Differentiation Transitamplifying cells Bulge (hair follicle stem cells) Epidermal stem cell FIGURE 17.20 Stem cells of the skin The epidermis consists of multiple layers of epithelial cells. Cells from the surface are continually lost and replaced by epidermal stem cells in the basal layer. The stem cells give rise to transit-amplifying cells, which undergo several divisions in the basal layer before differentiating and moving to the surface of the skin. Stem cells of hair follicles reside in a region beneath the sebaceous gland called the bulge, and distinct stem cells of the sebaceous gland reside at its base. which proliferate and differentiate to form the hair shaft. Finally, a distinct population of stem cells resides at the base of the sebaceous gland. It is notable that, if the skin is injured, stem cells of the bulge can also give rise to epidermis and sebaceous glands, demonstrating their activity as multipotent stem cells from which both skin and hair can be derived. Skeletal muscle provides an example of the role of stem cells in the repair of damaged tissue, in contrast to the continual cell renewal just d...
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