Gallbladder

Introduction

The gallbladder (or cholecyst, sometimes gall bladder) is a small organ whose function in the body is to store bile and aid in the digestive process.

Anatomy

The cystic duct connects the gall bladder to the common hepatic duct to form the common bile duct. This common bile duct then joins the pancreatic duct, and enters through the hepatopancreatic ampulla at the major duodenal papilla.

The fundus of the gallbladder is the part farthest from the duct, located by the lower border of the liver. It is at the same level as the transpyloric plane.

Microscopic anatomy

The different layers of the gallbladder are as follows:

• The gallbladder has a simple columnar epithelial lining characterized by recesses called Aschoff's recesses, which are pouches inside the lining.
• Under the epithelium there is a layer of connective tissue (lamina propria).
• Beneath the connective tissue is a wall of smooth muscle (muscularis externa) that contracts in response to cholecystokinin, a peptide hormone secreted by the duodenum.
• There is essentially no submucosa separating the connective tissue from serosa and adventitia.

Function

The gallbladder stores about 50 mL of bile, which is released when food containing fat enters the digestive tract, stimulating the secretion of cholecystokinin (CCK). The bile, produced in the liver, emulsifies fats and neutralizes acids in partly digested food.

After being stored in the gallbladder the bile becomes more concentrated than when it left the liver, increasing its potency and intensifying its effect on fats. Most digestion occurs in the duodenum.

Vertebrates have gallbladders, but invertebrates don't. This is because vertebrates eat in boluses while invertebrates are constantly eating. To digest a large bolus of food requires a large amount of digestive secretions, hence the presence of a gallbladder.

Diseases and disorders

• Cholecystitis
  
• Gallbladder cancer
• Strawberry gallbladder
• Gallstone
• Gallbladder polyp