Why are intestinal lining cells replaced so quickly?

The intestinal lining undergoes continuous cellular turnover because it is a high-wear environment that requires constant renewal to maintain its function.1

In the small intestine, this process is driven by stem cells located in small pits called crypts. These stem cells produce a large population of "transit amplifying cells" that divide rapidly and differentiate into the various cell types characteristic of the intestinal epithelium. As these new cells are produced, they migrate from the crypts onto the villi—the fingerlike projections of the intestinal lining—before eventually being shed into the lumen of the intestine. This cycle ensures that the lining is effectively and perpetually replaced.21