Anatomy, Abdomen and Pelvis: Biliary Ducts

Excerpt

Bile, a digestive fluid produced and secreted by the liver, is transported by a series of branching bile ducts known collectively as the biliary tree. At the cellular level, several narrow tubular channels called canaliculi collect the bile generated by each hepatocyte. These canaliculi drain into an intralobular bile duct which collects all the bile from each lobule, the functional unit of the liver. Intralobular ducts then drain into the interlobular ducts, which are located between lobules. The interlobular ducts merge to form the two main bile ducts of the liver: the right hepatic duct (RHD) and the left hepatic duct (LHD). Extrahepatically, the RHD and LHD coalesce to form the common hepatic duct (CHD), which travels within the hepatoduodenal ligament until coming into contact with the cystic duct, the bile duct, which connects to the gallbladder. The CHD and cystic duct merge to form the common bile duct (CBD). The hepatopancreatic ampulla, also called the hepatopancreatic duct or ampulla of Vater, is a spherical structure located at the site of the confluence of the common bile duct and pancreatic duct, marking the entry point of bile into the second portion of the duodenum. This is controlled by the smooth muscle fibers of the sphincter of Oddi, which opens at the duodenal papilla, allowing bile to flow into the small intestine. Alternatively, bile can travel into the gallbladder for storage via the cystic duct.

Intrahepatic Ducts

1. Canaliculi: Contain microvilli for increased surface area

2. Intralobular ducts: These ducts are located alongside the hepatic artery and the portal vein. Together, these three structures are referred to as portal triads and are ensheathed by a layer of connective tissue known as Glisson’s capsule

3. Interlobular ducts

4. Right hepatic duct: Drains right lobe of the liver (segments V, VI, VII, and VIII)

5. Left hepatic duct: Drains the left lobe of the liver (segments II, III, IV).

The caudate lobe of the liver (segment I) is drained by small ducts from both the right and left lobes.

Extrahepatic Ducts

1. Extrahepatic segments of the right hepatic and the left hepatic ducts

2. Common hepatic duct. Approximately 4 cm in length

3. Cystic duct: Outflow tract of the gallbladder. Approximately 7 mm in diameter. Contains valves of Heister

4. Common bile duct: Normal width should be less than approximately 6 mm. Approximately 6.0 cm to 8.0 cm in length.