Which structure secretes bile

Then, when food is eaten, the gallbladder contracts and releases stored bile into the duodenum to help break down the fats. Bile is the greenish-yellow fluid consisting of waste products, cholesterol, and bile salts that is secreted by the liver cells to perform 2 primary functions:. Bile salt is the actual component that helps break down and absorb fats. Bile, which is excreted from the body in the form of feces, is what gives feces its dark brown color.

Health Home Conditions and Diseases. The transportation of bile follows this sequence: When the liver cells secrete bile, it is collected by a system of ducts that flow from the liver through the right and left hepatic ducts. These ducts ultimately drain into the common hepatic duct. Bile is a complex fluid containing water, electrolytes and a battery of organic molecules including bile acids, cholesterol, phospholipids and bilirubin that flows through the biliary tract into the small intestine.

There are two fundamentally important functions of bile in all species:. Adult humans produce to ml of bile daily, and other animals proportionately similar amounts. The secretion of bile can be considered to occur in two stages:. In species with a gallbladder man and most domestic animals except horses and rats , further modification of bile occurs in that organ. The gall bladder stores and concentrates bile during the fasting state. Typically, bile is concentrated five-fold in the gall bladder by absorption of water and small electrolytes - virtually all of the organic molecules are retained.

Secretion into bile is a major route for eliminating cholesterol. Free cholesterol is virtually insoluble in aqueous solutions, but in bile, it is made soluble by bile acids and lipids like lecithin. Gallstones , most of which are composed predominantly of cholesterol, result from processes that allow cholesterol to precipitate from solution in bile. Bile acids are derivatives of cholesterol synthesized in the hepatocyte. Cholesterol, ingested as part of the diet or derived from hepatic synthesis is converted into the bile acids cholic and chenodeoxycholic acids, which are then conjugated to an amino acid glycine or taurine to yield the conjugated form that is actively secreted into cannaliculi.

Bile acids are facial amphipathic, that is, they contain both hydrophobic lipid soluble and polar hydrophilic faces. The cholesterol-derived portion of a bile acid has one face that is hydrophobic that with methyl groups and one that is hydrophilic that with the hydroxyl groups ; the amino acid conjugate is polar and hydrophilic. Hepatic synthesis of bile acids accounts for the majority of cholesterol breakdown in the body.

In humans, roughly mg of cholesterol are converted to bile acids and eliminated in bile every day. This route for elimination of excess cholesterol is probably important in all animals, but particularly in situations of massive cholesterol ingestion.