Gallbladder

The gallbladder is a small pear-shaped sac tucked under the liver that stores and concentrates bile produced by hepatocytes. Between meals, the sphincter of Oddi stays closed, so bile backs up through the cystic duct into the gallbladder, where water and electrolytes are absorbed, turning the fluid up to ten times more concentrated. When fatty food enters the duodenum, cholecystokinin triggers gallbladder contraction and sphincter relaxation, squirting bile into the intestine to emulsify fats for digestion. Gallstones can form from imbalanced cholesterol or bilirubin, blocking the duct and causing painful attacks.