Anatomy & physiology of gall bladder and biliary tree

Dr.Prashanth.S1stYear PG

Dept.of General Surgery

Introduction

• Component of extrahepatic biliary system along with

• Rt. and Lt.hepatic ducts• Common hepatic duct• Cystic duct• Common bile duct

Embryology

• Liver primordium begins to form in third week of IUL from caudal end of foregut.

• It elongates cranially and gives a small bud on right side-”pars cystica” and the main part gives rise to “pars hepatica”.

• From pars cystica gall bladder and cystic duct are formed.

• Initially extra hepatic biliary apparatus is occluded with endodermal cells which gets canalized in later period.

Gall bladder

• Pear shaped• 7-10cm long, 3cm broad.• 30-50 ml capacity.• When Obstructed 300ml.

Parts

• Fundus• Body• Infundibulum• neck

Anomalies of gall bladder

Cystic duct

• 3-4 cm long• Runs downwards,backwards and to

the left• Ends by joining CHD at an acute

angle to become CBD.• Mucous membrane of the cystic duct

forms a series of crescentic folds arranged spirally-spiral valve of Heister.

Anomalous connections of cystic duct with CHD.

Contd…

Biliary tree

• Right and left hepatic ducts• Common hepatic duct-3 cm, runs

downwards and is joined by cystic duct to form common bile duct.

• Accessory hepatic ducts present in about 5% of subjects.

• Usually come from right lobe of liver.and terminate either in gall bladder or CHD.

Variations in hepatic duct confluence

Calot’s triangle

Common bile duct

• 7-11 cm long,6-8mm in diameter.• 4 parts- Supraduodenal, Retroduodenal,

infraduodenal and intraduodenal.• Within the wall of duodenum

hepatopancreatic ampulla/ampulla of vater is formed by union of two ducts.

• Distal constricted end of ampulla opens at the summit of major duodenal papilla (8-10cm distal to pylorus.)

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Patterns of biliopancreatic duct insertion into duodenum

Histology

• Mucous membrane projects to form folds.

• Tall columnar epithelium• Lamina propria-loose connective tissue• Fibromuscular coat-smooth muscle

fibres,collagen fibres.• Serosa.• Lacks submucosa and muscularis

mucosa.

Blood supply

• Cystic artery-gall bladder,cystic duct,hepatic ducts,and upper part of bile duct.

• Posterior superior pancreaticoduodenal artery-lower part of bile duct.

• Right hepatic artery –minor source of middle part of bile duct.

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Anomalous origin of cystic artery

Venous drainage

• Superior surface of GB drains into hepatic veins.

• Rest of GB is drained by one or two cystic veins which enter into right branch of portal vein.

• Lower part of bile duct drains into portal vein.

Lymphatic drainage

• Cystic lymph node of Lund and node of anterior border of epiploic foramen

• Upper pancreaticosplenic nodes.

Nerve supply

• Cystic plexus of nerves • Right and left vagus nerves• Right phrenic nerve• Pain from GB may be referred to

stomach, inferior angle of right scapula, right shoulder.

USG

CT

MRI

ERCP

MRCP

PHYSIOLOGY

• Normal adult 500-1000ml/day.• Secretion of bile is responsive to

neurogenic,hormonal,chemical stimuli.

• Stimulators:HclPartially digested proteins, fatty

acids(via; secretin)Vagus stimulation

• Inhibitors:• Splanchnic nerve stimulation

Bile composition

• Bile is mainly composed of water, electrolytes, bile salts, proteins, lipids, and bile pigments. Sodium, potassium, calcium, and chlorine have the same concentration in bile as in plasma or extracellular fluid.

• pH of bile is neutral/slightly alkaline and it varies with diet.(proteins shifts it towards acidic).

• Ratio of bile acids: phosphatidyl choline: cholesterol is approx;10:3:1.

Bile formation

• Almost 95% of bile acid is reabsorbed and returned to liver via portal circulation-Enterohepatic circulation.

• Remaining 5% is excreted through stool and urine.

• FUNCTION: concentrate, store and regulate the flow of bile in response to meal.

• Function of bile is digestion and absorption of fats. Also it is the major excretory route for lipid soluble waste products.

Absorption and Secretion

• In fasting state 80% of the bile secreted by the liver is stored in the gall bladder.

• It rapidly absorbs sodium, chloride, and water, concentrating the bile as much as 10-fold.

• The epithelial cells of the gallbladder secrete two important products into the gallbladder lumen: glycoproteins and hydrogen ions.

• The acidification promotes calcium solubility, thereby preventing its precipitation as calcium salts

Motor activity• During fasting the gallbladder repeatedly

empties small volumes of bile into the duodenum which is mediated by motilin.

• In response to a meal, the gallbladder empties by a coordinated motor response of gallbladder contraction and sphincter of Oddi relaxation.

• One of the main stimuli to gallbladder emptying is the hormone cholecystokinin.

• When stimulated by eating, the gallbladder empties 50 to 70% of its contents within 30 to 40 minutes. Over the following 60 to 90 minutes, the gallbladder gradually refills.

Neurohormonal regulation• The vagus nerve stimulates contraction of the

gallbladder, and splanchnic sympathetic stimulation is inhibitory to its motor activity.

• Antral distention of the stomach causes both gallbladder contraction and relaxation of the sphincter of Oddi.

• Hormonal receptors are located on the smooth muscles, vessels, nerves, and epithelium of the gallbladder.

• CCK is released into the bloodstream by acid, fat, and amino acids in the duodenum.

• CCK has a plasma half-life of 2 to 3 minutes and is metabolized by both the liver and the kidneys.

Contd…• CCK acts directly on smooth muscle receptors of the gallbladder and stimulates gallbladder contraction.• CCK stimulation of the gallbladder and the biliary tree also is mediated by cholinergic vagal neurons. • In patients who have had a vagotomy, the

response to CCK stimulation is diminished and the size and the volume of the gallbladder are increased.

Sphincter of oddi• It is a complex structure that is functionally

independent from the duodenal musculature and creates a high-pressure zone between the bile duct and the duodenum.

• The sphincter of Oddi is about 4 to 6 mm in length and has a basal resting pressure of about 13 mmHg above the duodenal pressure.

• On manometry, the sphincter shows phasic contractions with a frequency of about four per minute and an amplitude of 12 to 140 mmHg.

• The spontaneous motility of the sphincter of Oddi is regulated by the interstitial cells of Cajal through intrinsic and extrinsic inputs from hormones and neurons acting on the smooth muscle cells.

Contd..

• Relaxation occurs with a rise in CCK, leading to diminished amplitude of phasic contractions and reduced basal pressure, allowing increased flow of bile into the duodenum.

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