What is the gallbladder?
The gallbladder is a long sac that stores bile produced by the liver. Sitting under the liver, the gallbladder controls the expulsion of bile into the duodenum plays an important role in the digestion of fats. It is not an essential organ and is often removed by a surgical procedure known as a cholecystectomy in cases of gallbladder disease or gallstones.
Anatomy of the Gallbladder
The gallbladder is a pear shaped organ that is about 7 to 10 centimeters long (3 to 4 inches) and 2 to 3 centimeters wide (about 1 inch). It has the ability to hold about 50 milliliters of bile which can be emptied via the cystic duct (gallbladder duct) into the common bile duct. From here, the bile will empty into the lumen of the duodenum. This is explained in detail under Bile Duct Anatomy.
The wall of the gallbladder has several layers including the epithelium (inner), lamina propria, muscularis, perimuscular and serosa (outer).
Parts of the Gallbladder
The gallbladder has 3 parts – fundus, body and neck. The fundus is the bottom of the gallbladder that protrudes from under the liver and visible anteriorly. The body is the main dilated portion of the gallbladder that lies between the fundus and cystic duct. The neck of the gallbladder is the narrower part that tapers into the cystic duct.
The cystic duct, which is about 3 to 4 centimeters long (about 1 to 2 inches), carries bile into the common bile duct.
Blood Supply and Lymphatic Drainage
Arterial blood supply to the gallbladder is via the cystic artery which arises from the right hepatic artery. Venous drainage is via the cystic veins – this mainly accounts for the drainage of the neck and cystic duct. The venous drainage of the body and fundus of the gallbladder is directly into the visceral surface of the liver and through the hepatic sinusoids. Lymph drains into the cystic lymph nodes which empty into the hepatic or celiac lymph nodes.
Nerves of the Gallbaldder
The nerve supply is via the :
- celiac plexus
- vagus nerve
- right phrenic nerve
These nerves contribute to the contraction of the gallbladder, relaxation of the relevant sphincters and pain.
Location of the Gallbladder
The gallbladder sits in the shallow gallbladder fossa on the visceral surface of the liver. Here the hepatic surface of the gallbladder is connected by connective tissue to the capsule surrounding the liver. The gallbladder is located in the right upper abdominal quadrant and the fundus of the gallbladder protrudes anteriorly from the inferior border of the liver. It is located around the 9th cost cartilage. The gallbladder also makes contact with the superior part of the duodenum and the transverse colon.
Picture from Wikimedia Commons
Functions of the Gallbladder
The primary functions of the gallbladder relates to the storage and secretion of bile.
- The gallbladder stores bile. It is also able to concentrate the bile from the liver so that the a large volume of the bile constituents can be stored in a small space (1 liter of bile concentrated into 50 ml).
- The gallbladder secretes bile by muscular contractions of its wall in response to both neural and hormonal factors stimulated by food, especially fatty foods, in the duodenum.