Extrahepatic Biliary System
Extrahepatic biliary system, as the name suggests, is the part of biliary system which is outside the liver. It includes right and left hepatic duct, common hepatic duct, Gall bladder, Cystic duct, Bile duct
- Right and left hepatic ducts unite at the right end of part a hepatis to form common hepatic duct. Common hepatic duct is 3 cm long and is joined by cystic duct (from its right side) to form Bile duct. Bile duct is about 8 cm long and passes downwards and 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 :-
- Supraduodenal part (above first part of duodenum):- This part lies in the free margins of lesser omentum. Its relations are:
- Anterior - Liver
- Posterior - Portal vein and epiploic foramen
- Left side - Hepatic artery
- Retro-duodenal part (Behind first part of duodenum) :-Its relations are:
- Anterior - 1st part of duodenum
- Posterior -IVC
- Left side - Gastroduodenal artery
- Infraduodenal part (Below first part of duodenum) :-Its relations are :
- Anterior - Head of pancreas
- Posterior - IVC
- 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.
Preampullary part of bile duct (terminal part of bile duct just before its junction with pancreatic duct) is surrounded by sphincter choledochus (sphincter of Boyden). This sphincter is always present. Terminal part of pancreatic duct (preamullary part of pancreatic duct) is surrounded by sphincter pancreaticus. Other sphincter surrounds hepatopancreatic ampulla, called sphincter of Oddi proper (sphincter ampulla). Actually all the three sphincter are considered as sphincter of Oddi.
Gall bladder and cystic duct
Gall bladder is a pear-shaped hollow viscous situated in a non-peritoneal fossa on the undersurface of right lobe of liver. It is 7-10 cm long, 3 cm broad and has a capacity of 30-50 mI.Gall bladder is divided into (from below upwards-fundus, body and neck. Fundus projects beyond the inferior border of liver. Body lies in the fossa for gallbladder on the undersurface of right lobe of liver. Neck is 'S' shaped and extends from the body to cystic duct, i.e. neck becomes continuous with cystic duct. From the neck, a small diverticulum known as Hartman's pouch projects downwards and backwards towards the duodenum. The wall of gall bladder is made up of mucous membrane, a fibromuscular coat~ and a serous layer that covers part of organ. The mucosa is noted for out pouchings extending into and through muscular fibers, called as Rokitansky-Aschoff sinuses.
Cystic duct is 3-4 cm in length and begins from the neck of gall bladder. It passes downwards, backwards and to left and ends by joining the right side of common hepatic duct at an acute angle to form bile duct. The interior of cystic duct presents about 5 to 12 crescentic valves known as spiral valves of Heister. Angle between the cystic duct and common hepatic duct contains cystic node.