Extrahepatic biliary system

EXTRAHEPATIC BILIARY SYSTEM 

• Part of biliary system which is outside the liver.

It includes:

1. right & left hepatic duct
2. Common hepatic duct
3. Gall bladder
4. Cystic duct
5. Bile duct

• Right & left hepatic ducts: unite at the right end of parta hepatis to form common hepatic duct.
• The right hepatic duct drains the bile ducts from segments V, VI, VII, and VIII, which constitute the right liver.
• Segment I (caudate) is drained by several small ducts.
• The left hepatic duct directly drains the bile ducts to segments II, III, and IV, which constitute the left liver. 
• Caudate lobe is usually drained by both left and right hepatic ducts.
• Common hepatic duct: 3 cm long & is joined by cystic duct (from its right side) to form Bile duct.

BILE DUCT:

• Bile duct is about 8cm long & passes downwards & backwards in the free margins of lesser omentum crosses posterior to 1st part of duodenum to open in 2nd part of duodenum after joining the pancreatic duct.

Bile duct is divided into following parts:

i. Supraduodenal part (above first part of duodenum):

• This part lies in the free margins of lesser omentum.                                                        

Its relations are:

1. Anterior→ Liver
2. Posterior→ Portal vein & epiploic vein
3. Left side→ Hepatic artery

ii. Retro-duodenal part (Behind first part of duodenum)

Its relations are:

1. Anterior→ 1st part of duodenum
2. Posterior→ IVC
3. Left side→ Gastroduodenal artery

iii. Infraduodenal part (Below first part of duodenum)

Its relations are:

1. Anterior→ Head of pancreas
2. Posterior→ IVC

iv.  Intraduodenal part (within second part of duodenum)

• In the wall of duodenum, bile duct unites with pancreatic duct to form hepatopancreatic ampulla (ampulla of Vater) which opens in 2nd part of duodenum at major duodenal papilla, 8-10 cm distal to pylorus.
• Preampulllary part of bile duct is surrounded by sphincter choledochus (sphincter of Boyden). This sphincter is always present.
• Terminal part of pancreatic duct (preampullary part of pancreatic duct) is surrounded by sphincter pancreaticus.
• Other sphincter surrounds hepatopancreatic ampulla, called Sphincter of Oddi proper (sphincter ampulla).
• All the three sphincter are considered as sphincter of Oddi.

• Its boundaries are formed by cystic duct (inferiorly), right lobe of liver (superiorly) & common hepatic duct (medially).

Contents of this triangle are:

1. Right hepatic duct
2. Right hepatic artery
3. Cystic artery→ In inferior part of triangle
4. Cystic lymph node of Lund

CYSTIC DUCT:

• 3-4 cm in length & begins from the neck of gall bladder.
• It passes downwards, backwards & to left & ends by joining the right side of common hepatic duct at an angle to form bile duct.
• The interior of cystic duct presents about 5 to 12 cresentic valves known as spiral valves of Heister.
• Angle b/w the cystic duct & common hepatic duct contains cystic lymph node.

Exam Question

 

• Segment I, the caudate lobe, has its own biliary drainage. Variations of this are common, and in 78% of individuals the caudate lobe drains into both the left and right hepatic duct.
• Pancreatic & bile duct open into duodenum at Ampulla of vater.
• Cell lining of common bile duct is Simple columnar.
• Common bile duct injuries are most commonly seen in Laparoscopic cholecystectomy operation.
• Onion skin” fibrosis of bile duct is seen in Primary sclerosing cholangitis.
• Cystic lymph node lies b/w cystic duct & common hepatic duct.
• Valves of Heister is seen in Cystic duct.
• Spiral valve is seen in Cystic duct.