Lecture 30- Monday, March 22 nd, 2010
Bile- Contains no digestive enzymes but is essential for the digestion of fats. It
contains the bile salts.Liver secretes bile, which is released into the duodenum from
3% solids- for every 100 mL of bile, there are 3 grams of solid. None of it is digestive
enzymes (unlike pancreatic juices).
Bile secretion by the liver is continuous: it releases about 0.5-1.0 L/day.
Entrance into the duodenum is intermittent, and the volume of bile entering is
<<<<<<<<0.5-1.0 L/day. How come?
During the interdigestive period, the Sphincter of Oddi is closed. As the liver keeps
secreting the bile, it encounters resistance and is reverted into the Gallbladder where
it is temporarily stored. Gallbladder has a capacity of about 50 mL. How does it fit all
500 mL? See picture below!
BILE SALTS are synthesized in the liver from CHOLESTEROL. These surface-acting
agents have the following properties:
1.They combine with fat-soluble substances to form water-soluble complexes
2.They reduce surface tension and stabilize emulsions
3.They assist in the transport and absorption of fat and fat-soluble Vitamins
Bile Salt Pool: 3.5 g
Daily synthesis: 0.5 g
Daily release into intestine: 15 – 20 g
Enterohepatic Circulation SLIDE 165
>90% actively reabsorbed in distal ileum.
10% escape into colon, where they undergo BACTERIAL MODIFICATION. A certain
proportion also gets reabsorbed.
Bile Salt Functions
regulate volume of bile secreted by liver