A physical and biochemical barrier that segregates host tissue and commensal bacteria to maintain intestinal homeostasis.Secretory IECs support this function through the secretion of mucins and antimicrobial peptides.
The mucosa of the small intestine is lined by a simple columnar epithelium which consists primarily of absorptive cells (enterocytes), with scattered goblet cells and occasional enteroendocrine cells. In crypts, the epithelium also includes Paneth cells and stem cells.  The epithelium of the villi is made up of tall columnar absorptive cells called enterocytes, and goblet cells, which secrete mucin, for lubrication of the intestinal contents, and protection of the epithelium. This shows the epithelium of part of a villus at high magnification. This is a diagram which shows the villi of the small intestine, as indicated by the arrows in the diagram above, at higher magnification. The main functions of the small intestine are digestion, absorption of food and production of gastrointestinal hormones. The small intestine is 4-6 metres long in humans. To aid in digestion and absorption: 1  the small intestine secretes enzymes and has mucous producing glands The Extrinsic Gastrointestinal Barrier. Mucus and Bicarbonate. The entire gastrointestinal epithelium is coated with mucus, which is synthesized by cells that form part of the epithelium. Mucus serves an important role in mitigating shear stresses on the epithelium and contributes to barrier function in several ways.  Key points. 1  Intestinal epithelial cells (IECs) provide a physical and biochemical barrier that segregates host tissue and commensal bacteria to maintain intestinal homeostasis. 2  Secretory IECs support this function through the secretion of mucins and antimicrobial peptides.  Intestinal Absorptive Cells. Absorptive cells, or enterocytes, are the predominant epithelial cell type lining the lumen of the small intestine and colon. These cells are specialized for absorption of nutrients across the apical plasma membrane and export of these same nutrients across the basal plasma membrane. Goblet cells are scattered among the absorptive cells in the epithelium of the small intestine and colon. These epithelial cells are specialized for secretion of mucus, which facilitates passage of material through the bowel. The name goblet refers to the cell's shape, narrow at the base and bulging apically Structure [edit]. The epithelium is part of the intestinal mucosa layer. In the small intestine this takes the form of villi but these are not present in the colon. In both parts of the mammalian intestine, the mucosa is covered by a single layer of epithelial cells that is renewed every 4–5 days. Intestinal epithelial cells are the cell boundary between the external environment and tissues of the gastrointestinal tract. From this interface the epithelial cells have evolved processes that help guide whether inflammation or an immune response will occur in the intestines. Architecture of the intestinal epithelium. The intestinal epithelium is a single‐cell thick layer of columnar epithelial cells lining the villi and crypts of the small intestine and crypts of the large intestine.
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function of intestinal epithelial cells