Extrahepatic Biliary Apparatus Study Notes

INTRODUCTION

  • Extrahepatic Biliary Apparatus:

    • Function: Collects bile from the liver, stores it in the gallbladder, and transmits it to the second part of the duodenum.

    • Components:

    • a. Right hepatic duct

    • b. Left hepatic duct

    • c. Common hepatic duct

    • d. Cystic duct

    • e. Gallbladder

    • f. Bile duct

    • Illustration Reference: Fig. 22.1.

DISSECTION

  • Location of Porta Hepatis:

    • Found on the inferior surface of the liver.

    • Identify the two hepatic ducts here and follow them to the common hepatic duct.

    • Note the cystic duct and gallbladder (green-colored), observing their junction with the common hepatic duct to form the bile duct.

    • Trace the bile duct towards the duodenum, taking note of its opening observed during duodenum dissection.

    • Trace the cystic artery which supplies the gallbladder, cystic duct, hepatic ducts, and the upper part of the bile duct.

RIGHT AND LEFT HEPATIC DUCTS

  • Emergence: The right and left hepatic ducts emerge at the porta hepatis from the right and left lobes of the liver.

    • Arrangement of Structures at the Porta Hepatis (from back to front):

    1. Branches of the portal vein

    2. Proper hepatic artery

    3. Hepatic ducts

    • Illustration Reference: Fig 22.2.

COMMON HEPATIC DUCT

  • Formation: Created by the union of the right and left hepatic ducts near the right end of the porta hepatis.

    • Direction: Runs downwards for about 3 cm, joining on its right side at an acute angle with the cystic duct to form the bile duct.

GALLBLADDER

  • Description:

    • Shape: Pear-shaped reservoir of bile.

    • Location: Positioned in a fossa on the inferior surface of the liver, extending from the right end of the porta hepatis to the inferior border of the liver.

    • Dimensions:

    • Length: 7 to 10 cm

    • Width: 3 cm at the widest point

    • Capacity: 30 to 50 ml.

    • Proximal Division:

    1. Fundus: Extends beyond the liver’s inferior border; surrounded by peritoneum; related to the anterior abdominal wall anteriorly and transverse colon posteriorly.

    2. Body: Lies within fossa; adherent to the liver at its superior surface; related to the beginning of the transverse colon and duodenum lower surface.

    3. Neck: The narrow upper end at the porta hepatis; curves anterosuperiorly, posteroinferiorly into cystic duct; marked by a spiral mucous membrane.

    • Hartmann's Pouch: An outpouching at the neck where gallstones may lodge.

CYSTIC DUCT

  • Description:

    • Length: About 3 to 4 cm.

    • Location: Begins from the neck of the gallbladder, running downwards and backwards to join the common hepatic duct.

    • Crescentic Folds: 5 to 12 spirally arranged folds (spiral valve of Heister) prevent obstruction; not a true valve.

FUNCTION OF GALLBLADDER

  • 1. Storage of bile, releasing it into the duodenum as needed.

  • 2. Absorption of water, concentrating bile by as much as ten times.

  • 3. Absorption of small amounts of loose bile salt-cholesterol compounds.

    • Inflammation Effect: Abnormal concentration function leads to bile salts absorption and cholesterol retention, promoting gallstone formation.

  • 4. Regulation of pressure in the biliary system through appropriate dilatation/contraction, maintaining normal choledocho-duodenal mechanism.

BILE DUCT

  • Formation: Union of the cystic and common hepatic ducts near the porta hepatis.

    • Length: 8 cm; Diameter: About 6 mm.

  • Course:

    1. Runs downwards and backwards in the free margin of the lesser omentum (supraduodenal part).

    2. Passes behind the first part of the duodenum (retro-duodenal part).

    3. Lies hidden within the head of the pancreas (infraduodenal part).

    4. Contacts the pancreatic duct; they accompany each other through the duodenal wall into the lumen of the duodenum (intraduodenal part).

RELATIONS OF BILE DUCT

  • Supraduodenal Part:

    1. Anterior: Liver.

    2. Posterior: Portal vein and epiploic foramen.

    3. Left: Hepatic artery.

  • Retro­duodenal Part:

    1. Anterior: First part of duodenum.

    2. Posterior: Inferior vena cava.

    3. Left: Gastroduodenal artery.

  • Infraduodenal Part:

    1. Anterior: Groove in the upper/lateral posterior surface of the head of the pancreas.

    2. Posterior: Inferior vena cava.

SPHINCTERS RELATED TO BILE AND PANCREATIC DUCTS

  • Sphincter Choledochus: Ring of smooth muscle surrounding the terminal bile duct; prevents bile from entering the duodenum until food intake.

  • Sphincter Pancreaticus: Less developed sphincter around the pancreatic duct, variable number.

  • Sphincter Ampullae or Sphincter of Oddi: Surrounds the hepatopancreatic ampulla; regulates bile and pancreatic fluid entry into the duodenum.

ARTERIAL SUPPLY OF THE BILIARY APPARATUS

  • Cystic Artery: Chief blood source, supplies gallbladder, cystic duct, hepatic ducts and upper part of the bile duct.

  • Pancreaticoduodenal Arteries: Supply lower part of bile duct.

  • Right Hepatic Artery: Minor source to the middle bile duct.

VENOUS DRAINAGE

  • Gallbladder:

    1. Superior surface drained by veins entering the liver, joining tributaries of hepatic veins.

    2. Lower part by cystic veins opening into right branch of the portal vein.

  • Bile Duct: Drains into the portal vein.

LYMPHATIC DRAINAGE

  • Gallbladder and associated ducts: Drained to cystic node and anterior border nodes of epiploic foramen; cystic node enlarged in cholecystitis.

  • Lower bile duct: Drains into lower hepatic and upper pancreatic-splenic nodes.

NERVE SUPPLY

  • Cystic Plexus: Derived from hepatic plexus, receives fibers from:

    1. Celiac plexus

    2. Left and right vagus nerves

    3. Right phrenic nerve

  • Parasympathetic Nerves: Motor to musculature; inhibit sphincters.

  • Sympathetic Nerves: From thoracic segments T7 to T9; vasomotor and motor to sphincters.

REFERRED PAIN FROM THE GALLBLADDER

  • Pain pathway:

    • Travels via vagus nerve to epigastrium.

    • Travels via sympathetic nerves to the inferior angle of the right scapula.

    • Travels through phrenic nerve to right shoulder (C4).

CLINICAL CONSIDERATIONS

  • Murphy's Sign: Diagnostic sign of cholecystitis; sharp pain on inspiration when palpating below the 9th costal cartilage.

  • Cholecystitis: Inflammation presenting with right hypochondrium pain, potentially radiating to shoulder or scapula.

  • Gallstones: Form in the gallbladder (cholelithiasis), present in 0.5% of subjects, particularly in females over 40; diet-dependent prevalence.

  • Cholecystectomy: Surgical removal of the gallbladder requiring awareness of anatomical variations in the biliary apparatus.

COURVOISIER'S LAW

  • Definition: Dilatation of the gallbladder occurs only in extrinsic obstruction of bile duct, e.g., pancreatic cancer pressure; intrinsic obstructions (gallstones) do not cause dilation due to fibrosis.

BILIARY OBSTRUCTION

  • Causes:

    1. Gallstones blocking the bile duct.

    2. Cancer of the pancreas compressing the bile duct.

    • Symptoms: Light-colored stools, dark-colored urine, jaundice indicate obstructive issues, with pain linked to gallstones.