The intestinal epithelium is the epithelium that covers the small and large intestine. It is simple columnar and nonciliated.
They primarily take part in the digestive system. However, they also express TLR 4 receptors, and are thus a part of the immune system, both as a barrier and as a first-line pathogen recognition system. The mammalian intestine is covered by a single layer of epithelial cells that is renewed every 4–5 days. Proliferative cells (Stem Cells) reside in the crypts of Lieberkühn (epithelial invasions into the underlying connective tissue). New cells are formed in the crypts of Lieberkühn which then migrate upwards and upon reaching the tip of the villus undergo apoptosis, getting shed off into the intestinal lumen.
Epithelial cells in the small intestine are a type of brush border cell that are joined together by tight junctions to form a polymer impermeable membrane. These cells have a brush border surface to increase their absorptive surface area, thus making them more efficient.
Genes important for the formation of intestinal epithelium are listed in this table.
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