Enterohepatic circulation refers to the circulation of biliary acids, bilirubin, drugs or other substances from the liver to the bile, followed by entry into the small intestine, absorption by the enterocyte and transported back to the liver.
Bile salts and lecithin are synthesized in the liver and help solubilize fat in the small intestine. During the digestion of a fatty meal, most of the bile salts entering the intestinal tract via the bile are absorbed by specific Na+ coupled transporters in the ileum. The non-polar portions of phospholipids and bile salts associate with the non-polar interior of lipid droplets, leaving the polar portions exposed at the water surface. They repel other lipid droplets that are similarly coated with these emulsifying agents, thereby preventing their reaggregation into larger fat droplets. The coating of lipid droplets with emulsifying agents speeds up the digestion of lipids by the action of lipase mediated by colipase (binds lipase and holds it on lipid surface).
The absorbed bile salts are then returned via the portal vein to the liver, where they are once again secreted into bile. Uptake of bile salts from portal blood into hepatocytes is driven by secondary active transport coupled to Na+. During the digestion of a meal, the entire bile salt content of the body may be recycled several times by enterohepatic circulation.
Bile salts and lecithin are synthesized in the liver and help solubilize fat in the small intestine. During the digestion of a fatty meal, most of the bile salts entering the intestinal tract via the bile are absorbed by specific Na+ coupled transporters in the ileum. The non-polar portions of phospholipids and bile salts associate with the non-polar interior of lipid droplets, leaving the polar portions exposed at the water surface. They repel other lipid droplets that are similarly coated with these emulsifying agents, thereby preventing their reaggregation into larger fat droplets. The coating of lipid droplets with emulsifying agents speeds up the digestion of lipids by the action of lipase mediated by colipase (binds lipase and holds it on lipid surface).
The absorbed bile salts are then returned via the portal vein to the liver, where they are once again secreted into bile. Uptake of bile salts from portal blood into hepatocytes is driven by secondary active transport coupled to Na+. During the digestion of a meal, the entire bile salt content of the body may be recycled several times by enterohepatic circulation.
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