Bile flows out of the liver through the right and left hepatic ducts (see Biology of the Liver and Gallbladder: Blood Supply of the Liver), which come together to form the common hepatic duct. This duct then joins with a duct coming from the gallbladder, called the cystic duct, to form the common bile duct. The pancreatic duct joins the common bile duct just where it empties into the duodenum through the sphincter of Oddi.
Between meals, bile salts are stored in the gallbladder, and only a small amount of bile flows into the intestine. Food that enters the duodenum triggers a series of hormonal and nerve signals that cause the gallbladder to contract. As a result, bile flows into the duodenum and mixes with food contents.
Bile has two important functions: It assists in the digestion and absorption of fats, and it is responsible for the elimination of certain waste products from the body—particularly hemoglobin from destroyed red blood cells and excess cholesterol. Specifically, bile is responsible for these actions:
Bile salts are reabsorbed by the last portion of the small intestine, extracted by the liver, and resecreted into bile. This recirculation of bile salts is known as the enterohepatic circulation. All the bile salts in the body circulate about 10 to 12 times a day. During each pass, small amounts of bile salts reach the large intestine, where bacteria break them down into various constituents. Some constituents are reabsorbed; the rest are excreted with the stool.
Last full review/revision August 2006 by Nicholas J. Shaheen, MD, MPH