Bile is secreted by the liver. It contains bile salts, bilirubin, and cholesterol. Bile acids are synthesized from cholesterol in hepatocytes and conjugated with taurine or glycine to make bile salts. They play a critical role in digestion of triglycerides. In the small intestine bile salts mix with triglycerides to make tiny particles. This emulsification allows pancreatic lipase to digest the triglycerides. Bilirubin is a yellow breakdown product of the hemoglobin pigment (heme) from old red cells that is produced by the spleen.
Bile is secreted into bile canaliculi between the hepatocytes. It empties into bile ductule that join to form the bile ducts of the hepatic triad. These collect bile and empty into the common hepatic duct that passes by the gallbladder, where it is stored and concentrated.
When needed, bile is released from the liver and squirted out from the gallbladder as it contracts. It flows through the cystic duct from the gallbladder which joins the hepatic ducts to form the common bile duct. Ducts from the pancreas, liver, and gallbladder enter the first part of the small intestine (duodenum) at the sphincter of Oddi. After bile has completed its role in triglyceride digestion, the bile salts are recycled back to the liver through the hepatic portal vein (the enterohepatic circulation).
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