Enterosit

Enterosit, or enterocytes, are the principal absorptive cells of the intestinal epithelium, lining the villi of the small intestine and, to a lesser extent, the surface of the large intestine. They are tall, columnar cells with a dense apical brush border formed by microvilli that greatly increases surface area for nutrient uptake.

These cells originate from intestinal stem cells (often labeled as Lgr5+) located at the crypts of Lieberkühn. They migrate up the villus, differentiate, and mature as they progress toward the tip, where they are shed and replaced. The turnover time for enterocytes in the small intestine is typically about three to five days.

The main function of enterocytes is nutrient and water absorption. The apical membrane houses transporters and enzymes for digestion and uptake, including SGLT1 and GLUT family transporters for glucose, amino acid and peptide transporters, and brush border enzymes such as lactase and sucrase–isomaltase. Fat absorption involves micelle formation, uptake of fatty acids, and assembly of triglycerides into chylomicrons that enter the lymphatic system. The basolateral side exports absorbed nutrients to the bloodstream or lymphatics and helps maintain electrolyte and fluid balance.

Enterocytes also contribute to barrier defense and innate immunity. They form tight junctions to limit paracellular leakage and can secrete antimicrobial peptides while participating in antigen handling and, via transcytosis of IgA, mucosal immune surveillance. They interact dynamically with the gut microbiota and respond to luminal signals with metabolic and immune changes.

Clinical relevance includes enteropathies such as celiac disease, infectious enteritis, and chemotherapy-induced mucositis, where enterocyte function and integrity are compromised.