The gallbladder is a pear-shaped sac lying on the undersurface of the liver. It has a capacity of 30 to 50 mL and stores bile, which it concentrates by absorbing water.
The gallbladder is divided into the fundus, body, and neck.
The fundus is rounded and projects below the inferior margin of the liver, where it comes in contact with the anterior abdominal wall at the level of the tip of the 9th right costal cartilage.
The body lies in contact with the visceral surface of the liver and is directed upward, backward, and to the left.
The neck becomes continuous with the cystic duct, which turns into the lesser omentum to join the common hepatic duct, to form the bile duct. The peritoneum completely surrounds the fundus of the gallbladder and binds the body and neck to the visceral surface of the liver.
When digestion is not taking place, the sphincter of Oddi remains closed and bile accumulates in the gallbladder. The gallbladder concentrates bile; stores bile; selectively absorbs bile salts, keeping the bile acid; excretes cholesterol; and secretes mucus.
To aid in these functions, the mucous membrane is thrown into permanent folds that unite with each other, giving the surface a honeycombed appearance. The columnar cells lining the surface have numerous microvilli on their free surface.