Biliary system and gall bladder

• The biliary system is a network of ducts that transport bile from the liver to the gallbladder and then to the small intestine. The system is divided into intrahepatic (within the liver) and extrahepatic (outside the liver) components.
• Extrahepatic Biliary Ducts

  The extrahepatic ducts transport bile from the liver and gallbladder to the duodenum.

  • Consists of:
  • Right + left hepatic ducts
  • Common hepatic duct
  • Gallbladder
  • Cystic duct
  • Bile duct

  
• • Bile is continuously produced by liver
  • Biliary ducts convey bile from liver to duodenum
  • Between meals, bile accumulates and is stored in gallbladder, which concentrates bile by absorbing water and salts
  • When fat enter duodenum, gallbladder contracts to release concentrated bile through biliary ducts to duodenum
  • Bile emulsifies fat so that it can be absorbed in intestine.
• intrahepatic biliary system: network of ducts within liver that collects bile produced by hepatocytes and drains in extrahepatic biliary system.

  • Bile Canaliculi: Tiny channels located between adjacent hepatocytes. hepatocytes secretes bile into it
  • Intrahepatic Ductules: Connect bile canaliculi to interlobular bile ducts.
  • Interlobular Bile Ducts: Located within portal triads of the liver lobules.
  • Intrahepatic Bile Ducts (Segmental Ducts): Larger ducts within liver that collect bile from multiple interlobular ducts. These ducts eventually merge to form the right and left hepatic ducts.

  
• • Right and left hepatic ducts drains right and left parts of liver
  • Shortly after leaving porta hepatis, these 2 hepatic ducts unite to form common hepatic duct, which joins on the right side to cystic duct to form common bile duct which conveys bile to duodenum.

  
• • The common bile duct = common hepatic duct + cystic duct.

  Course: common bile duct descends from junction of the common hepatic duct and cystic duct → travels downward through hepatoduodenal ligament (part of lesser omentum) running alongside with portal vein and proper hepatic artery → passes posteriorly to first part of duodenum →continues through head of pancreas or along a groove on its posterior surface unites with main pancreatic duct to form hepatopancreatic ampulla, which opens into the duodenum through major duodenal papilla

  
• The circular muscle around the distal end of common the bile duct is thickened to form the sphincter of the bile duct . When this sphincter contracts, bile cannot enter the ampulla and the duodenum; hence, bile backs up and passes along the cystic duct to the gallbladder for concentration & storage

  
• The bile duct is supplied as the following :

  • proximal part is supplied by: cystic artery
  • middle part is supplied by: the right hepatic artery .
  • distal part is supplied by: the posterior superior pancreaticoduodenal artery gastroduodenal artery .
• The hepatic ducts and proximal part of bile duct usually drain to liver directly or through hepatic portal vein .

  • The distal part of bile duct is drained by posterior superior Pancreaticoduodenal vein that empties into hepatic portal vein .
• Gallbladder

  • 7-10 cm long pear-shaped organ
  • Lies in fossa of gallbladder on viceral surface of liver
  • Stores and concentrates bile
  • Has 3 pars: fundus, body and neck (joins cystic duct)

  
• • Peritoneum completely surrounds the fundus of the gallbladder and binds its body and neck to the liver.
  • Hepatic surface of gallbladder attaches to the visceral surface of liver by connective tissue of the fibrous capsule of the liver .
• Fundus of gallblader

  • is the wide blunt end of gallbladder .
  • projects from inferior border of the liver at the tip of right 9th costalcartilage
  • completely surrounded by the visceral peritoneum

  
• Body of the gallbladder : is the main portion of gallbladder .

  • Related to: visceral surface of liver, transverse colon. superior part of the duodenum

  
• Neck of the gallbladder : narrow, tapering end of gallbladder .

  • makes an S-shaped bend and joins the cystic duct.
  • At the junction of neck of the gallbladder & cystic duct, the mucosa begins to spiral into folds (called the spiral folds of Heister)

  
• The cystic duct : is a 3-4 cm long duct .

  • connects the neck of the gallbladder to the common hepatic duct .
  • passes between the layers of the lesser omentum, usually parallel to the common hepatic duct .

  joins the common hepatic duct to form the bile duct .

  • has the spiral folds in its proximal part

  
• • The spiral folds of Heister helps keep the cystic duct open; thus bile can easily be diverted into the gallbladder when the distal end of the bile duct is closed by the sphincter of the bile duct, or bile can pass to the duodenum as the gallbladder contracts
  • The spiral fold also offers additional resistance to sudden dumping of bile when the sphincters are closed, and intra-abdominal pressure is suddenly increased, as during a sneeze or cough .
• Arterial supply of the gallbladder & cystic duct

  • Cystic artery: branch of right hepatic artery
• Venous drainage of the gallbladder & cystic duct

  • The neck of gallbladder and cystic duct are drained by small, multiple cystic veins, that join the right branch of hepatic portal vein .
  • The fundus and body of gallbladder are drained by small veins that pass directly into the visceral surface of the liver and drain into the hepatic sinusoids
• Lymphatic drainage of the gallbladder & cystic

  duct:

  The lymphatic vessels from the gallbladder & cystic duct pass to : cystic lymph node (near the neck of the gallbladder) + hepatic lymph nodes ...
• Sphincter of oddi

  • circular muscular layer
  • surronds major duodenal papulla
  • controls flow of bile, pancreatic enzymes
  • prevents reflux.
• Acini lobules


  Zone I: closer to portal triad. Affected by viral hepatitis first.

  Zone II

  Zone III: most vulnerable to ischemia. Fat accumulation begins here in alcoholic liver disease, high concentration of P459 enzymes in hepatocytes.

  
• Bile duct