Stem cells are undifferentiated cells that divide and produce more stem cells or progenitor cells that differentiate into mature, specialized cell types. All the cells in the body are generated from stem cells in the early embryo, but small populations of stem cells are also present in many adult tissues including the bone marrow, brain, skin, and gut. These adult stem cells typically produce the various cell types found in that tissue—to replace cells that are damaged or to continuously renew the tissue.
The epithelium lining the small intestine is continuously renewed by adult stem cells. It is the most rapidly replaced tissue in the human body, with most cells being replaced within 3-5 days. The intestinal epithelium consists of thousands of villi that protrude into the interior of the small intestine—increasing its surface area to aid in the absorption of nutrients.
Intestinal stem cells are located at the base of invaginations called crypts that lie between the villi. They divide to produce new stem cells, as well as daughter cells (called transit amplifying cells) that divide rapidly, move up the villi and differentiate into all the cell types in the intestinal epithelium, including absorptive, goblet, enteroendocrine, and Paneth cells. These mature cells continue to move up the villi as they carry out their functions, except Paneth cells which move back down to reside at the base of the crypt.
When the mature cells reach the top of the villi, they undergo apoptosis—programmed cell death—and are shed. New cells continue to push up from below, continuously replacing the cells that are lost.
Из главы 15:
Now Playing
Biotechnology
27.7K Просмотры
Biotechnology
72.4K Просмотры
Biotechnology
51.6K Просмотры
Biotechnology
92.4K Просмотры
Biotechnology
30.4K Просмотры
Biotechnology
26.0K Просмотры
Biotechnology
21.5K Просмотры
Biotechnology
13.5K Просмотры
Biotechnology
190.0K Просмотры
Biotechnology
24.7K Просмотры
Biotechnology
29.5K Просмотры
Biotechnology
48.0K Просмотры
Biotechnology
28.8K Просмотры
Biotechnology
203.3K Просмотры
Biotechnology
35.0K Просмотры
Авторские права © 2025 MyJoVE Corporation. Все права защищены