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Updated: 03/13/08 01:44 PM |
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| HOME | HEAL | EDUCATE | RESEARCH | DIRECTORY | OUTREACH |
Authors: W. Volwiler, R.A. Willson, A.M. Larson, and J.D. Ostrow
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Download Chapter ♦ Download Lecture Slides & Notes
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E. Gross and Microscopic Structure of the Extrahepatic Ductal System |
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| Common duct diameter is < 7 mm |
The right and left hepatic ducts, gallbladder, cystic duct and common bile duct comprise the extrahepatic ductal system (Figure 7). Emerging from the hilum of the liver (porta hepatis), the right and left hepatic bile ducts join to form the common hepatic duct. The cystic duct arises from the common hepatic duct and connects it to the gallbladder. The continuation of the hepatic duct from the cystic duct to the papilla of Vater is the common bile duct. The diameter of the common bile duct is usually less than 7 mm.
The gallbladder is a pear-shaped hollow viscus attached in part to the under surface of the right lobe of the liver. It consists of fundus, a body, and a neck which is continuous with the cystic duct. There are remarkable variations in the size and shape of the gallbladder, and on occasion, it may be contained entirely within the substance of the liver. |
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| Gallbladder epithelium absorbs and secretes fluids and electrolytes |
Microscopically, the gallbladder wall consists of an epithelial surface, lamina propria, muscular layer and serosa (it lacks a submucosa). Its lumen is lined with columnar epithelial cells, that are separated by large intercellular spaces, sealed apically by tight junctions. These spaces, and the tightly packed microvilli on the apical surfaces (brush border), facilitate the extensive transfer of fluid and electrolytes across the gallbladder epithelium. The mucosa is thrown into folds by contractions of the muscular layer. The folds may form deep pockets, but in the normal gallbladder these pockets do not extend into the muscular layer. However, in chronic cholecystitis, these pockets extend into and beyond the muscular layer, and are called Rokitansky-Aschoff sinuses; these are of diagnostic importance to the surgical pathologist.
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| Stones may impact in the neck of the gallbladder |
The circular muscles in the neck of the gallbladder throw the mucosa into spiral folds - the valves of Heister. These spiral valves are especially prominent at an S-shaped bend formed by the connection of the neck with the cystic duct and they are commonly visualized during contrast studies involving the gallbladder. It is in this region that gallstones become impacted in acute/chronic cholecystitis.
The lumen of the extrahepatic bile ducts is lined with tall columnar epithelium. Beneath the epithelium is a fibroelastic layer in which are variable amounts of smooth muscle fibers. Mucous glands lie in the deeper parts of this fibroelastic layer. The outer portion of the extrahepatic bile duct wall is composed of an adventitia containing nerves, lymphatics and vascular ramifications. |
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Figure 7 Anatomy of bile ducts, gallbladder, duodenum and pancreas. From Cholangiography and Pancreatography, by M. Ohta, et al., Eds. Igaku-Shoin Ltd.,Tokyo, University Park Press, Baltimore, 1978. |
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Next Section (F): Function of Components of the Liver » |
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