Gall Bladder

The gall bladder is easily visualized in the fetal pig as a green sac attached to the dorsal side of the liver.
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The gall bladder further provides an excellent example of structure meeting function in the storage and production of bile. The structures that come off of the gall bladder perfectly complements its function of storing bile. the cystic duct comes out of the gall bladder and merges with the common bile duct, which functions to place bile into the small intestine for fat digestion. The hepatic duct then comes out of the liver and also merges with the common bile duct, allowing a direct source of bile into the small intestine.

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The gall bladder fits the definition of smooth muscle, since it is stimulated by the presence of fat in the small intestine, and then contracts, sending the bile into the small intestine. It is not under the conscious control of the human brain, meaning that the brain cannot simply tell the gallbladder to secrete the bile into small intestine. The homeostatic control of the bile-gallbladder-liver system or BGL is accomplished through a negative feedback mechanism, where too much bile in the small intestine inhibits bile secretion from the gallbladder.

One of the biggest diseases associated with the gallbladder in both human and animal is the formation of gallstones. Gallstones are small pieces of hard matter created when the liquid bile hardens in the gallbladder. The treatment is the removal of the gallbladder, which in turn, removes the body's storage capacity for bile. However, the structure of the hepatic duct allows direct bile secretion to the small intestine. Therefore, as long as the liver is not overly stimulated, the loss of the gallbladder is not very traumatic.