Biliary system (overview)
The biliary system is a series of various ducts and organs involved in the production, storage, transportation and release of bile into the small intestine to aid digestion. These include the gallbladder and various bile ducts forming the biliary tree, as well as various associated structures of the digestive system, such as the liver. However, the main structures are the bile ducts and gallbladder.
The biliary tree (biliary tract) is a system of ducts that collect and transport bile from the liver to the duodenum (Read more!). Overall, the biliary tree is composed of two parts - the intrahepatic ducts found inside the liver and the extrahepatic ducts located outside the liver.
The extrahepatic part of the biliary tree connects with the gallbladder - a pear-shaped sac-like organ that stores and concentrates bile. The gallbladder lies on the visceral surface of the liver. It joins the common hepatic duct (Read more!) via the cystic duct (Read more!), forming the common bile duct (Read more!).
The bile is a yellowish-green liquid that helps with digestion and absorption of fats and fat-soluble vitamins (K, E, D, A) in the small intestine. Bile also neutralizes excess stomach acid and helps to remove lipid-soluble waste products.
The main components of bile include water, cholesterol, bile salts, amino acids, enzymes, and bilirubin. Bilirubin gives the bile its color and is also responsible for the pigmentation of feces.
The bile is released into the descending part of the duodenum to aid in the digestion of fats by breaking them into smaller fat droplets. This process happens as a response to the stimulation via the hormone called cholecystokinin. It is secreted by cells of the proximal small intestine due to the presence of food within the intestines.