Gall bladder, muscular sac in many vertebrate animals that stores the bile created by the liver. In humans the pear-shaped sac lies in its own depression, or foss, under the liver. It is about 3.5 in (9 cm) long, 1 in (2.5 cm) wide, and holds about 35 cu cm of fluid. Arising from the gall bladder is the cystic duct, which is connected to the liver by the common hepatic duct, and to the first part of the small intestine, the duodenum, by the common bile duct. In the presence of fatty foods in the small intestine, a hormone, cholecystokinin, produced by the cells of the small intestine, causes the gall bladder to contract and empty its contents into the duodenum. Cholecystitis (inflammation of the gall bladder resulting from infection by bacteria) can be acute or chronic. In most instances, acute cholecystitis is caused by a gallstone blocking the cystic duct. Chemical irritation and the digestive activities of certain enzymes can also play a contributing role. A sharp pain in the right upper part of the abdomen is a prominent symptom. The condition may require surgical removal of the gall bladder. The chronic condition is sometimes associated with cancer of the gall bladder.