The gallbladder is an intraperitoneal organ derived from the endoderm that is located inferior to the liver. It is divided into a fundus, a body, and a neck. The gallbladder is perfused by the cystic artery, a branch of the right hepatic artery that drains into the cystic vein and the hepatic sinusoids. It receives sympathetic innervation via the celiac plexus, parasympathetic innervation via the vagus nerve, and sensory innervation via the branches of the phrenic nerve. The main function of the gallbladder is bile storage. Bile is secreted by the liver and facilitates digestion, neutralization of gastric acid, fat absorption, and excretion of bilirubin and cholesterol. The biliary tract, which is divided into intrahepatic and extrahepatic bile ducts, transports bile to the intestine. The ductules are intrahepatic bile ducts that unite to form the left and right hepatic ducts, which drain bile from the liver. The extrahepatic bile ducts include the cystic duct and the common hepatic duct, which unite to form the common bile duct. The common bile duct unites with the pancreatic duct and drains into the hepatopancreatic ampulla in the duodenum. Excessive saturation of bile with cholesterol or bilirubin leads to gallstone formation. Diseases of the biliary tract include cholecystitis, primary sclerosing cholangitis, and biliary atresias among many others.
The gallbladder is a hollow, pear-like-shaped (piriform) organ that lies on the cystic plate (gallbladder bed) under the liver segments IVB and V. The cystic plate is a fibroareolar tissue that attaches the superior surface of the gallbladder to the liver.
- Location: intraperitoneal organ
Size and volume
- Length: 7–10 cm
- Width: 2.5 cm (at its widest point)
- 30–35 mL under normal conditions
- Can hold up to 300 mL if the cystic duct is obstructed
- Storage of bile
- Concentration of bile: by absorption of electrolytes and water
- Arterial blood supply: cystic artery (branch of the right hepatic artery)
- Venous drainage
- Sympathetic: via the celiac plexus
- Parasympathetic: hepatic branch of the vagus nerve
- Sensory: fibers from the phrenic nerve → referred pain to the right shoulder area (via C3 nerve fibers)
Layers of the gallbladder wall 
- Serosa (on the inferior peritoneal surface) and adventitia (on the superior hepatic surface)
- Muscularis externa
- Lamina propria
The biliary tree is divided into the intrahepatic and extrahepatic bile ducts.
Intrahepatic bile ducts
- Bile canaliculi → intrahepatic bile ductules (canals of Hering) → segmental bile ducts → sectional ducts
- Common hepatic duct (CHD): formed by the right and left hepatic ducts
Extrahepatic bile ducts
- Common bile duct
Hepatobiliary triangle (Calot triangle)
- An anatomical space formed by the common hepatic duct, the cystic duct, and the lower border of the liver
- The Calot triangle contains the cystic artery and the cystic lymph node (Lund's node).
- During cholecystectomy, the Calot triangle must be carefully identified to prevent damage to the cystic artery and extrahepatic biliary system.
- Bile pigments
- Primary bile acids
Secondary bile acids
- Deoxycholic acid, lithocholic acid
- Synthesized in the intestinal lumen by the action of bacterial flora
- Bile acids are conjugated with glycine or taurine to form bile salts and become water-soluble.
- Other components: phospholipids, cholesterol, water, and ions
- Emulsion and absorption of fats (including )
- Excretion of bilirubin and cholesterol (the process by which the majority of cholesterol is removed from the body)
- Antimicrobial effect (may disrupt bacterial membranes)
- Transport of IgA
- Bile salts (∼ 95% of bile acids are reabsorbed back into the liver to be recycled)
There are different types of gallstones (see “” and “” for more information):
- Cholesterol stones (∼ 80% of cases)
- Pigment gallstones
- Derived from endoderm
- Starts to develop during the 4th week of embryonic development
- Formed from the hepatic diverticulum (hepatic bud)
- See “Embryology of the gastrointestinal tract” for more information.
Disorders of the biliary tract
- Cholesterolosis (cholesterol deposits within macrophages, which causes a yellowish, speckled mucosal coloration due to excess cholesterol in bile)