Bile is a complex liquid secreted by the liver that helps promote the digestion and absorption of fats.

It also contains waste products excreted by the liver. Bile leaves the liver through the hepatic ducts and empties into the duodenum via the bile duct.

The gall bladder is a side-arm of this system and acts as a reservoir where bile can be stored and concentrated.

The presence of fat in the duodenum stimulates the gall bladder to contract and empty bile down the cystic duct into the bile duct.