Bile Salt Recycling in Enterohepatic Circulation
- Bile salts pass down the length of the small intestine to the ileum
- Reabsorbed into circulation at the ileum (they the enter recycling pathway: enterohepatic circulation).
- Travel through the hepatic portal vein back to the liver where they are recycled and re-secreted into newly formed bile.
Note: The hepatic portal vein drains nutrient-rich blood from the small intestine to the liver for metabolic processing.
- Small amount of bile salts continues through the rest of the digestive tract; approximately 5% of bile salts are eliminated in feces (along with other bile components).
Note: The liver synthesizes more bile salt from cholesterol to account for its loss.
Enterohepatic Circulation
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Bile Salt Recycling in Enterohepatic Circulation
- Bile salts pass down the length of the small intestine to the ileum
- Reabsorbed into circulation at the ileum (they the enter recycling pathway: enterohepatic circulation).
- Travel through the hepatic portal vein back to the liver where they are recycled and re-secreted into newly formed bile.
Note: The hepatic portal vein drains nutrient-rich blood from the small intestine to the liver for metabolic processing.
- Small amount of bile salts continues through the rest of the digestive tract; approximately 5% of bile salts are eliminated in feces (along with other bile components).
Note: The liver synthesizes more bile salt from cholesterol to account for its loss.
Bile Secretion
Regulated by secretin and CCK
Secretin
- Secreted from the duodenum in response to acidic chime in the duodenum
- Acts on the liver to stimulates bile secretion.
- Bile (which contains bicarbonate) neutralizes the acidic chyme.
- Secreted from duodenum in response to fatty acids present in the chyme
- Acts on the gallbladder – produces gallbladder contraction
- Acts on sphincter of Oddi to promote its relaxation
- Thus, stimulates bile flow into the duodenum - the bile salts (another major component of bile) can emulsify fats (like a detergent) for their digestion and subsequent absorption in the small intestine.
Note: bile also contains cholesterol, lecithin (phospholipids), bile pigments, and trace metals.