Anatomy and physiology of gall bladder

anatomy and physiology

1. ANATOMY AND PHYSIOLOGY OF GALL BLADDER

2. EMBRYOLOGY Genesis of gall bladder and cystic duct from distal portion of hepatic diverticulum(pars cystica) By end of 4 th week of intrauterine life, cystic duct and gall bladder primordium produced from pars cystica of hepatic diverticulum By 5 th week all elements of biliary tree recognisable

3. ANATOMY A part of extrahepatic biliary system Pear-shaped sac 7-10 cm long Average capacity of 30 to 50 ml Distension upto 300 ml in obstruction Location- fossa on inferior surface of liver on segments IVb and V

4. ANATOMY Anatomic areas- fundus, body, infundibulum, and neck Fundus - rounded, blind end,extends 1 to 2 cm beyond liver’s margin Fundus contains most of smooth muscles Body-main storage area and contains elastic tissue

5. ANATOMY Neck -deepest part of gallbladder fossa, extends into free portion of hepatoduodenal ligament Infundibulum-angulated posterior part If dilated with eccentric buldging of medial aspect – Hartmann’s pouch

6. HISTOLOGY Layers from external to internal- serosa,adventitia,fibromuscular layers,mucosa Lacks muscularis mucosa and submucosa Muscle layer has poorly developed circular, longitudinal and oblique fibers Adventitia contains connective tissue, nerves, vessels, lymphatics, adipocytes

7. HISTOLOGY Mucosa lined by single, tall,slender columnar epithelium This layer thrown into folds, forming deep diverticula into muscularis named “Rokitansky- Aschoff sinuses” Tubuloalveolar glands in mucosa of infundibulum and neck secretes mucus

8. BLOOD SUPPLY Main blood supply -Cystic artery from right hepatic artery Small arterial branches from parenchyma of segment IV or V of liver protect gallbladder from ischaemic necrosis in thrombosis of cystic artery At neck ,two to four minor branches ( calot arteries) supplying cystic duct On superior aspect of neck , cystic artery divides : - superficial branch (anterior) passing subserously to left of gall bladder - deep branch (posterior) between gall bladder and liver parenchyma Branches anastomose over surface of body and fundus

9. BLOOD SUPPLY Origin of cystic artery is variable Most common variant is origin from right hepatic artery Rarely from left hepatic, gastroduodenal, superior pancreaticoduodenal, coeliac, right gastric or superior mesenteric arteries but cystic artery may not traverse Calot’s triangle

10. BLOOD SUPPLY Venous supply from multiple small cystic veins Hepatic surface drained by small veins through gall bladder bed into liver Those from superior surface of body and neck drain into segmental portal veins within liver Rest drained by one or two small cystic veins into either portal branches in liver or portal tributaries draining hepatic ducts and upper bile duct

11. LYMPHATIC DRAINAGE Subserosal and submucosal vessels drain into cystic and pericholodochal node Primary drainage areas from here- retroportal and posterosuperior pancreaticoduodenal nodes Then course to celiac, superior mesenteric and interaortocaval nodes Lymphatics on hepatic aspect connect directly with intrahepatic lymph vessels ( subcapsular)

12. NERVE SUPPLY Preganglionic sympathetic level is T8 and T9 Impulses pass by sympathetic afferent fibers through splanchnic nerves and mediate biliary colic Postganglionic sympathetic fibres from coeliac and superior mesenteric ganglia are inhibitory Contraction occurs in response to parasympathetic (vagal) stimulation Hepatic branch of vagus nerve supplies cholinergic fibers

13. ANOMALIES Classic description of extrahepatic biliary tree and its arteries applies only in one third of patients Gallbladder may have abnormal positions Buried within liver (intrahepatic )or suspended by peritoneal mesentery (torsion ) Partial or totally intrahepatic is associated with increased incidence of cholelithiasis Rudimentary, anomalous forms, duplicated Isolated congenital absence of the gallbladder is very rare( 0.03% )

14. ANOMALIES OF GALL BLADDER Phrygian cap –common anomaly where fundus is folded upon body,present in 5% of cases Congenital diverticulum of gallbladder with muscular wall be found Left-sided gallbladder with cystic duct emptying into left hepatic duct rare Incidence of duplication with 2 separate cavities and 2 separate cystic ducts - 1 in ever 4000 persons Duplication occurs in 2 major varieties More common form in which each gallbladder with its own cystic duct emptying independently into same or different parts of extrahepatic biliary tree

15. ANOMALIES OF GALL BLADDER

16. CYSTIC DUCT Arises from neck or infundibulum and extends to join common hepatic duct Mucosa of cystic duct arranged in spiral folds known as valves of Heister Lumen measures 1 to 3 mm Length around 3cm but varies depending on union with common hepatic duct Joins supraduodenal segment of common hepatic duct in 80% of cases

17. ANOMALIES OF CYSTIC DUCT

18. ECTOPIC DRAINAGE INTO GALL BLADDER AND CYSTIC DUCT

19. ANOMALIES OF CYSTIC ARTERY

20. CALOT’S TRIANGLE Boundaries: -superiorly by inferior surface of liver, -laterally by cystic duct and medial border of gallbladder -medially by common hepatic duct Contents-right hepatic artery, cystic artery,lymph node of lund , lymphatics Important surgical landmark as cystic artery usually can be found within it Most dangerous anomaly is tortuousity of right hepatic artery with or without short cystic artery known as ‘caterpillar turn’ or ‘Moynihan’ hump’ An aberrant right hepatic duct-most common anomaly

21. CALOT’S TRIANGLE

22. PHYSIOLOGY OF GALL BLADDER Main function of gall bladder:- -Concentration and storage of bile -Delivery of bile into duodenum in response to meal -secretion of mucus upto 20ml per day Normal adult produces 500-1000ml/day Bile composition -water, electrolytes, bile salts,proteins , lipids, bile pigments pH of bile is usually neutral In fasting state ,80% of bile secreted by liver stored in gallbladder

23. PHYSIOLOGY OF GALL BLADDER Secretion responsive to neurogenic, humoral, and chemical stimuli Hydrochloric acid, partly digested proteins, and fatty acids in duodenum increases bile production and flow through secretin Gallbladder mucosa has the greatest absorptive power per unit area of any structure in body Rapid absorption prevent rise in pressure within biliary system normally

24. Epithelial cells secrete glycoproteins and hydrogen ion Glycoproteins protect mucosa from lytic action of bile and facilitate passage of bile through cystic duct Transport of hydrogen ions leads to a decrease in bile pH Acidification promotes calcium solubility ,preventing precipitation as calcium salts

25. MOTOR ACTIVITY OF GALL BLADDER Filling facilitated by tonic contraction of sphincter of Oddi creating pressure gradient between bile ducts and gallbladder Empties by coordinated motor response contraction and sphincter of Oddi relaxation in response to meal Main stimuli to gallbladder emptying is hormone cholecystokinin (CCK) CCK acts directly on smooth muscle receptors and stimulates gallbladder contraction CCK released into bloodstream by acid, fat, and amino acids in duodenum

26. NEUROHORMONAL REGULATION Hormonal receptors located on smooth muscles, vessels, nerves, epithelium Vagus nerve stimulates contraction of gallbladder Splanchnic stimulation inhibitory to motor activity Antral distention of stomach causes gallbladder contraction and relaxation of sphincter of Oddi Hormonal receptors located on smooth muscles, vessels, nerves, and epithelium of gallbladder Neurohormonal Regulation. The vagus nerve stimulates contraction of the gallbladder, and splanchnic sympathetic

27. NEUROHORMONAL REGULATION Stimulators of contraction:- -Parasympathomimetic drugs -CCK Inhibitors of contraction:- -Somatostatin and its analogues -Vasoactive intestinal polypeptide Atropine leads to relaxation Patients treated with somatostatin analogues, somatostatinoma have high incidence of gallstones due to inhibition contraction and emptying Defects in motor activity are thought to play role in gallstone formation

28. EFFECT OF CHOLECYSTOKININ ON GALL BLADDER

29. THANK YOU