The cystic duct runs backwards and downward from the neck of the gallbladder to run in the lesser omentum with common hepatic duct and joins it at an acute angle to create the bile duct. It is about 3-5 cm in length.
It meets common hepatic duct, generally situated immediately below the porta hepatis.
The cystic duct is mucous membrane lined by a series of crescentic folds on the inside (5-10 in number). They project into the lumen in a spiral manner creating a spiral fold termed “spiral valve (of Heister)”.
The valve of Heister keeps the duct open so that bile can go through it both in and out of the gallbladder.
When the CBD is closed at its inferior end, the bile secreted by the liver fills the duct and goes through the cystic duct into the gallbladder.
When the CBD is open, the bile flows into it from the common hepatic and cystic ducts.
The flow of bile is enhanced by the contraction of the gallbladder. It’s organised by the easiness of sphincter of CBD below the effect of cholecystokinin, a hormone released by the duodenal mucosa.