The gallbladder (or cholecyst sometimes gall bladder) is a pear-shaped organ that stores about 50 mL of bile (or "gall") until the body needs it for digestion. The gallbladder is about 7-10cm long in humans and is dark green in appearance due to its contents (bile), not its tissue. It is connected to the liver and the duodenum by the biliary tract.
Anatomy
Not all mammals have gallbladders. The rat and horse, for example, do not have a specialized organ for the storage of bile. The gallbladder is connected to the main bile duct through the gallbladder duct (cystic duct or, in Latin, ductus cysticus). The main biliary tract runs from the liver to the duodenum, and the cystic duct is effectively a "cul de sac", serving as entrance and exit to the gallbladder. The surface marking of the gallbladder is the intersection of the mid-clavicular line (MCL) and the transpyloric plane, at the tip of the ninth rib. The blood supply is by the cystic artery and vein, which run parallel to the cystic duct. The cystic artery is highly variable, and this is of clinical relevance since it must be clipped and cut during a cholecystectomy.
Microscopic anatomy
The gallbladder has an epithelial lining characterised by recesses called Aschoff's recesses, which are pouches inside the lining. Under the epithelium there is a layer of connective tissue, followed by a muscular wall that contracts in response to cholecystokinin, a peptidehormone secreted by the duodenum.
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