What Does the Gallbladder Do?
The gallbladder stores and concentrates bile during fasting, then contracts after meals to deliver bile into the duodenum for digestion, while also protecting the body from toxic bile acids. 1
Primary Functions
Storage and Concentration
- The gallbladder stores bile during the fasting state, with the sphincter of Oddi maintaining higher pressure in the common bile duct than in the duodenum or gallbladder, preventing bile from flowing out prematurely. 1
- The organ concentrates bile between meals, making it more potent for digestive purposes when needed. 2
Coordinated Bile Delivery
- The gallbladder empties mainly after eating (postprandially) through coordinated contraction of the gallbladder and simultaneous relaxation of the sphincter of Oddi. 1
- This emptying is controlled by both hormonal and neural mechanisms, with cholecystokinin (CCK) being the principal hormone controlling gallbladder emptying after meals. 1
- CCK is produced in the proximal small bowel after food ingestion and binds to receptors in the gallbladder causing contraction while relaxing the sphincter of Oddi, leading to increased bile flow into the intestine. 1
Protective Function
- The accumulation of primary bile acids (cholic acid and chenodeoxycholic acid) in the gallbladder reduces the formation of secondary bile acids (deoxycholic acid and lithocholic acid), protecting the liver, stomach mucosa, gallbladder, and colon from their toxic hydrophobic effects. 3
- The gallbladder epithelium secretes bicarbonate and mucins, which provide cytoprotection against bile acids. 2
Additional Regulatory Functions
Bile Composition Regulation
- The gallbladder contributes to regulating bile composition through unique absorptive and secretory capacities. 2
- The epithelium can absorb cholesterol and provides a cholecystohepatic shunt pathway for bile acids. 2
- After feeding, fluid transport reverses from absorption to secretion, occurring together with bicarbonate secretion in response to neurohormonal factors like vasoactive intestinal peptide. 2
Clinical Context
Timing Considerations
- The gallbladder contracts 5-20 minutes after food enters the stomach, while gastric chyme moves from stomach to duodenum 1-3 hours later, suggesting the gallbladder's role in digestion may be less significant than its protective functions. 3
Impact of Gallbladder Removal
- Cholecystectomy increases the enterohepatic recirculation rates of bile acids, leading to metabolic effects and an increased risk of nonalcoholic fatty liver disease, cirrhosis, and small-intestine carcinoid, independently of gallstone presence. 2