1. Liver, biliary system, pancreas and spleen
Long Nguyen

2. Embryology of the digestive glands
Liver, gallbladder and pancreas develop from endodermal diverticulae that bud from the duodenum in the 4th to 6th weeks
Liver sprouts first and expands in ventral mesentery
Cystic diverticulum also in ventral mesentery
Pancreas arises from a dorsal and ventral bud.
Ventral pancreatic bud migrates posteriorly to fuse with the dorsal bud.
Main duct of ventral bud becomes the main pancreatic duct.

3. Liver - exam questions
Write short notes on the segmental anatomy of the liver. (9/07, 9/05, 4/05, 9/04, 9/02)
Write short notes on the arterial supply to the liver and its normal variants. (9/08, 10/01)

4. Liver Lies in right upper quadrant. Underlies the thoracic cage.
Conforms to right dome of diaphragm
Connected to the diaphragm by the falciform and coronary ligaments

5. Liver - relations
Surfaces separated by inferior border of liver and coronary ligament posteriorly
Bare area between the reflections of coronary ligaments in direct contact with diaphragm and not covered by peritoneum
Diaphragmatic surface
Smooth and convex
Separated from diaphragm by subphrenic recess

6. Liver – relations (2) Visceral (posteroinferior) surface
Lies in contact with oesophagus, stomach and lesser omentum on the left
Duodenum in midline
Right kidney, adrenal and hepatic flexure of the colon on the right
H-shaped arrangement of structures
Crossbar formed by porta hepatis (portal vein, hepatic artery, hepatic ducts, nerve plexus and lymph vessels
Left: ligamentum teres (remnant of left umbilical v.) and ligamentum venosum (remnant of ductus venosum)
Left umbilical v. carries blood from placenta to foetus.
Ductus venosum shunts blood form the left umbilical vein to the IVC in the foetus bypassing the liver.

8. Liver - old lobar anatomy
Right and left lobes divided by plane through the IVC and gallbladder fossa on (Moore)
Caudate lobe
Lies posteriorly between lig. venosum and IVC fossa
Porta hepatis inferiorly
Tail-like caudate process connects to right lobe and separates portal vein from IVC
Quadrate lobe
Anteroinferior between GB bed and lig. teres
Porta hepatis superiorly
Caudate and quadrate lobe considered to be part of left lobe
Reidel’s lobe (not a true lobe)
Lower border of the right lobe lateral to the GB may project downwards for a considerable distance as a broad or bulbous process
Occurs in 5-10% of females and rarely in males
Even older anatomy
Falciform ligament anteriorly and lig. teres and venosum on visceral surface
Caudate and quadrate lobe considered to be part of right lobe

9. Liver - vascular anatomy
Double blood supply from hepatic artery (30%) and portal vein (70%)
Arterial supply by common hepatic artery branch of coeliac artery.
Gives off right gastric and gastroduodenal arteries before reaching the liver in the free edge of the lesser omentum.
Divides into left and right hepatic arteries before entering the liver at the porta.
Variants of right hepatic artery below
Portal vein formed posterior to neck of pancreas by union of SMV and splenic vein
Hepatic a. carries oxygenated blood and conducted to central v of each liver lobule
Portal v carries venous blood containing products of digestion absorbed from the GI tract.

10. Liver - vascular anatomy (2)
Right and left lobes functionally independent and defined by arterial distribution
Each supplied by left and right portal v., left or right hepatic arteries and drained by left or right hepatic duct (portal triad)
Quadrate lobe supplied by left hepatic artery
Caudate lobe supplied by both

11. Liver - hepatic veins
Hepatic veins are intersegmental and do not run with the structures of the portal triad
Right, middle and left hepatic veins drain corresponding thirds of the liver
Middle hepatic vein lies in the principal plane between right and left lobes
Left hepatic vein lies between medial and lateral segments of the left lobe
Right hepatic vein lies between anterior and posterior segments of the right lobe
All drain into the IVC without an extrahepatic course
Inferior group of small veins from right lobe also drains into IVC

12. Liver - segmental anatomy (Couinaud system)
Knowledge of segments important in the assessment of location and extent of hepatic pathology as surgery is performed in segmental fashion and distribution of disease determines whether lesions are resectable.
The hepatic veins divide the liver into 4 divisions
A horizontal plane through the portal vein divides the 4 divisions into superior and inferior segments
Segments numbered in clockwise direction starting at caudate lobe (segment 1)

13. Liver – Lymph drainage and innervation
Superficial and most deep lymph vessels converge at the porta and end in the hepatic lymph nodes (eg. Cystic LN near GB neck or LN of omental foramen)
Hepatic LN’s drain into coeliac LN’s around the coeliac trunk, then thoracic duct
Some deep lymph vessels follow hepatic veins to IVC foramen in diaphragm and end in middle phrenic LN’s
Innervation
Sympathetic and parasympathetic supply from the hepatic plexus, a derivative of coeliac plexus (formed from fibres of left and right vagus and right phrenic nerves)

14. Gallbladder and biliary tree – exam questions
Write short notes on the anatomy of the gall bladder (9/04)
Write short notes on the anatomy of the biliary tree (excluding the gallbladder) and normal variations (4/08, 9/07, 4/05)

15. Gallbladder and cystic duct
Pear shaped sac lies to the right of the quadrate lobe in GB fossa on the visceral surface of liver
Concentrates and stores bile secreted by the liver
Cholecystokinin produced by intestinal mucosa during digestion, passes to GB and causes it to contract and release bile
Fundus, body and neck
Mucosal membrane arranged into spiral folds (valves of Heister) at GB neck and cystic duct

16. Gallbladder - relations
Anterosuperiorly
GB fossa of liver
Fundus projects from inferior border of liver, located at tip of 9th costal cartilage in MCL where lateral edge of rectus abdominis meets costal margin
Posteroinferiorly
Neck: lesser omentum. Omental (epiploic) foramen lies immediately to the left.
Body: D1
Fundus: transverse colon

17. Gallbladder – blood supply
Arterial supply
cystic artery
Venous drainage
directly into liver or via a cystic vein

18. Biliary Tree
Bile is secreted by hepatocytes into bile canuliculi which drain into interlobular bile ducts. Progressively larger ducts formed.
Left and right hepatic ducts emerge from porta and merge to form common hepatic duct (4cm)
Joined on the right by the cystic duct from the GB to form the common bile duct (8-10cm long, 5-6mm diameter)
Runs in free edge of lesser omentum, passes posterior to D1 and head of pancreas
Comes in contact with pancreatic duct on the left side of D2
Usually unite in the duodenal wall to form hepatopancreatic ampulla (of Vater)
Ampulla opens into descending part of duodenum at summit of major duodenal papilla, 8-10cam from pylorus
Areas drained by hepatic ducts are the same as those supplied by the accompanying portal v. and hepatic a.
Choledochal sphincter surrounds the bile duct as it penetrates the duodenal wall
Hepatopancreatic sphincter (sphincter of Oddi) at distal end of hepatopancreatic ampulla controls release of both bile and pancreatic fluid

19. Biliary Duct – blood supply
Arterial supply
Proximally: cystic artery
Middle: right hepatic artery
Distally: posterior superior pancreaticduodenal a.
Venous drainage
Proximally: drainage directly into liver
Distally: posterior superior pancreaticduodenal v.
Lymph drainage
Cystic LN, node of omental foramen, hepatic LN’s

20. Biliary Tree - variants
Accessory hepatic ducts may arise in the liver and join the right hepatic duct, common hepatic duct, common bile duct, cystic duct or GB
Right and left hepatic ducts may fail to unite giving a double duct
Cystic duct
Absent
Joins common hepatic duct on the left rather than the right
Joins the right hepatic duct or an accessory duct
Joins the common hepatic duct anywhere between the porta and the duodenum (low and high union)

21. Variants in union of CBD and pancreatic duct

22. Pancreas – exam questions
Write short notes on the anatomy of the pancreatic ducts and variations. (9/08)
Make brief notes on the embryology of the pancreas. (10/00)
What sonographic landmarks are useful in identifying the pancreas? (10/00) Describe the sonographic appearance of a normal pancreas.

23. Pancreas
Retroperitoneal organ lies transversely and slightly obliquely at L1-L2 level
Transverse mesocolon attached to anterior margin
Exocrine (pancreatic enzymes) and endocrine functions (glucagon and insulin)
Head, neck, body and tail

24. Pancreas - Relations Head Neck Body Tail Lies in curvature of duodenum
Anterior to IVC, aorta, right renal vessels and left renal vein
Uncinate process projects posteriorly and to the left and lies posterior to superior mesenteric vessels
CBD passes posteriorly in a groove or embedded within
Neck
Anterior to the union of splenic vein and SMV to form the portal vein
Body
Curves over vertebrae and great vessels
Anterior to the aorta and lies between the coeliac trunk and the SMA
Splenic vein passes posterior
Tail
lies in the splenorenal ligament
Usually contacts the hilum of the spleen

26. Pancreas - Embryology
Arises from the junction of the primitive foregut and midgut as a larger dorsal division and a smaller ventral bud
Ventral bud swings posteriorly to unite with the inferior aspect of the dorsal bud trapping the superior mesenteric between divisions
Ventral bud forms the uncinate process
Duct of the ventral bud forms the proximal end of the main pancreatic duct; the distal end of the dorsal pancreatic duct forms the remainder.

27. Pancreas - variations

28. Pancreas – blood supply
Arterial supply
Head: superior pancreaticoduodenal a. (from gastroduodenal artery) and inferior pancreaticoduodenal a. (from SMA)
Body and tail: branches from splenic artery
Venous drainage
Mostly splenic v., but also portal v. and SMV

29. Spleen Large soft vascular lymphatic organ in the left upper quadrant
Up to 12cm with long axis in line with 10th rib
Arises from mass of mesenchymal cells located between layers of dorsal mesogastrium.

30. Spleen - relations
Posterior to stomach. Connected to greater curvature by gastrosplenic ligament
Anterior to superior part of left kidney. Connected by splenorenal ligament
Laterally: diaphragm, 9th-11th left ribs
Tail of pancreas lies at splenic hilum

31. Spleen – blood supply Arterial supply Venous drainage Lymph drainage
Splenic artery divides into end arteries as it enters the spleen
No anastamoses, hence obstruction of one end artery results in area of splenic infarction
Venous drainage
Splenic vein
Lymph drainage
Pancreaticopsplenic LN’s