Re: What does the gallbladder do?

The function of the gallbladder is to concentrate, store, and release bile, and to add to it some secretory products (e.g., mucous substances). About 800–1000 mL of bile flows daily into the gallbladder from the liver. Because of its effective concentrative function the gallbladder (with a capacity of 40–70 mL) can handle a much larger volume of bile.

Release of bile from the gallbladder occurs in response to a meal. Filling of the gallbladder is the result of specific neural and hormonal stimuli that coordinate the relaxation of the gallbladder wall and the closing of the ampullary sphincter(the Doyon reflex). The ampullary sphincter where the bile duct joins the duodenum. Bile enters the gallbladder when pressure in the common bile duct is greater than intraluminal gallbladder pressure; however, the gallbladder does not simply fill passively and continuously during fasting. Periods of filling are interrupted by brief periods of partial emptying of concentrated bile and aspiration of diluted bile in a bellows-like fashion. In the fasting state, up to 50% of the daily bile production bypasses the gallbladder to enter the duodenum.

The gallbladder contracts and empties when fats enter the duodenum. Cholecystokinin is released from the small intestine; it represents the most important hormone for promoting gallbladder contraction and simultaneous relaxation of the ampullary sphincter. Other hormones (eg, motilin, bombesin, substance P) assist in gallbladder contraction, whereas pancreatic polypeptide and somatostatin slow contraction.

Where the gall bladder joins the bile duct there isn't just a tube connection but a spiral valve. Tweet