[L. bilis, bile]
A thick, viscid, bitter-tasting fluid secreted by the liver. It passes from the hepatic duct of the liver either to the cystic duct of the gallbladder or to the common bile duct to the duodenum. The bile from the liver is straw-colored; that from the gallbladder varies from yellow to brown to green.
Bile is stored in the gallbladder, where it is concentrated, and discharged into the duodenum when fatty chyme enters from the stomach. Contraction of the gallbladder is brought about by cholecystokinin-pancreozymin (a hormone produced by the duodenum); its secretion is stimulated by the entrance of fatty foods into the duodenum. Added to water, bile decreases surface tension, providing a foamy solution favoring the emulsification of fats and oils. This action is due to the bile salts, mainly sodium glycocholate and taurocholate.
Bile pigments (principally bilirubin and biliverdin) are responsible for the variety of colors observed. In addition, bile contains cholesterol, lecithin, mucin, and other organic and inorganic substances.
The function of bile in digestion is to emulsify fats, facilitating their digestion in the small intestine by pancreatic lipase. Bile also stimulates peristalsis. Normally the ejection of bile occurs only during duodenal digestion. About 800 to 1000 ml/24 hr are secreted in the normal adult.
Interference with the flow of bile causes jaundice and the presence of unabsorbed fats in the feces.
There's more to see -- the rest of this topic is available only to subscribers.