Proliferative cells residing at the base of the crypts of Lieberkühn produce new epithelial cells which migrate upwards and out of the crypt. Eventually, they are shed into the intestinal lumen.
Boumphreyfr
CC BY-SA 3.0
<a href="//commons.wikimedia.org/wiki/File:Epithelial_shedding.png" title="File:Epithelial shedding.png">File:Epithelial_shedding.png</a>