Lecture 4

• Pancreas

  An elongated, accessory digestive gland
• Liver

  The largest gland in the body, weighs approximately 1500g and accounts for approximately one-fortieth of adult body weight
• Pancreas

  • Secondary retroperitoneal organ
  • Transversely across the posterior abdominal wall
  • Lies posterior to the stomach between the duodenum on the right and the spleen on the left
  • The transverse mesocolon attaches to its inferior margin
• Parts of the pancreas

  • Head
  • Neck
  • Body
  • Tail
• Pancreas - neck

  • Overlies the superior mesenteric vessels, which form a groove in its posterior aspect
  • The anterior surface is covered with peritoneum, is adjacent to the pylorus of the stomach
  • Posterior to its the superior mesenteric vein joins with the splenic vein to form the portal vein
• Pancreas - body

  • Continues from the neck and lies to the left of the superior mesenteric vessels
  • Passing over the aorta and L2 vertebra
  • The anterior surface is covered with peritoneum and forms part of the stomach bed
  • The posterior surface is devoid of peritoneum and is in contact with aorta, superior mesenteric artery, left suprarenal gland, left kidney and renal vessels
• Pancreas - tail

  • Lies anterior to the left kidney
  • Is closely related to the hilum of the spleen and the left colic flexure
  • Is relatively mobile and passes between the layers of the splenorenal ligament
  • The tip of tail is usually blunted and turned superiorly
• Main pancreatic duct (duct of Wirsung)

  • Begins in the tail and runs through the parenchyma of the gland to the head
  • In the head turns inferiorly and is related to the bile duct
  • Unites with the bile duct to form hepatopancreatic ampulla
  • The sphincter of its, the sphincter of the bile duct and the hepatopacreatic sphincter (sphincter of Oddi) are smooth muscle sphincters that control the flow of bile and pancreatic juice into descending part of duodenum (major duodenal papilla, Vater papilla)
• Accessory pancreatic duct (duct of Santorini)

  • Drains the uncinate process and the inferior part of the head of the pancreas
  • Opens into the duodenum at the summit of the minor duodenal papilla
  • Usually communicates with the main pancreatic duct
  • In some cases is greater than the main pancreatic duct and the two are not connected so it carries most of the pancreatic juice
• Arteries of the pancreas

  • Body and tail: splenic artery (10 branches)
  • Head: superior pancreaticoduodenal artery: anterior and posterior, inferior pancreaticoduodenal artery (anterior and posterior branch)
• Veins of the pancreas

  • Are tributaries of the splenic and superior mesenteric parts of the portal vein
  • Most of them empty into the splenic vein
• Lymphatic vessels of the pancreas

  • Follow the blood vessels
  • Most of them end in the pancreaticosplenic nodes that lie along the splenic artery
  • Some of them end in the pyloric lymph nodes
  • Efferent vessels from the pancreaticosplenic nodes and pyloric nodes drain to the celiac, hepatic and superior mesenteric lymph nodes
• Nerves of the pancreas

  • Derived from the vagus and thoracic splanchnic nerves passing through the diaphragm
  • The fibers passing along the arteries from the celiac plexus and superior mesenteric plexus to pancreatic acinar cells and islets passing parenchymal (sympathetic and parasympathetic) fibers and to vasa passing vasomotor (sympathetic) fibers
• Liver

  • Lies inferior to the diaphragm, which separates it from the pleura, lungs, pericardium and heart
  • Has many metabolic activities, stores glycogen and secretes bile
• Surface anatomy of the liver

  • Lies mainly in the right upper quadrant
  • Is hidden and protected by the thoracic cage and diaphragm
  • Lies deep to ribs 7 through 11 on the right side and crosses the midline toward the left niple
  • Occupies most of the right hypochondriac, epigastric and extends into the left hypochondriac region
• Surfaces of the liver

  • Diaphragmatic Surface
  • Visceral surface (posteroinferior)
  • Surfaces are separated anteriorly by its sharp inferior border
  • Is covered by the subperitoneal fibrous capsule (Glisson's capsule)
• Diaphragmatic surface of the liver

  • Is smooth and dome-shape
  • Is largely separated from the diaphragm by the subphrenic recesses between the anterior part of liver and the diaphragm
  • Is covered with visceral peritoneum except posteriorly in the bare area of the liver
• Hepatorenal recess (Morison's pouch)

  • Is a deep recess on the right side extending superiorly between the liver anteriorly and the kidney and suprarenal gland posteriorly, fluid draining from the omental bursa flows into the recess
  • Communicates anteriorly with the right subphrenic recess
• Bare area of the liver

  • The liver lies in contact with the diaphragm
  • Is demarcated by the reflection of peritoneum from the diaphragm to it as the anterior (upper) and posterior (lower) layers of the coronary ligament
• Visceral surface of the liver

  • Right and left sagittal fissure
  • Is covered with visceral peritoneum except at the bed of the gallbladder and the porta hepatis
  • Is related to the stomach, superior part of duodenum, lesser omentum, gallbladder, right colic flexure and the right transverse colon, right kidney and suprarenal gland
• Functional parts of the liver

  • The segmentation of the liver is based on the principal divisions of the hepatic artery proper and portal vein and accompanying hepatic ducts
  • Has functionally independent right and left parts (portal lobes, right and left liver) that are approximately equal in size
  • On the visceral surface the right liver is demarcated from the left liver by the gallbladder fossa inferiorly and the fossa for the inferior vena cava superiorly
  • Each part has its own blood supply from the hepatic artery and portal vein and its own venous and biliary drainage
• Anatomical (nonfunctional) lobes of the liver

  • Right lobe
  • Left lobe
  • Quadrate lobe
  • Caudate lobe
• The liver - the left lobe

  • Is separated from caudate and quadrate lobes on the visceral surface by the fissure for round ligament of the liver and the fissure for the ligamentum venosum
  • Is separated on the diaphragmatic surface by the attachment of the falciform ligament
• Round ligament of the liver

  Is the fibrous remnant of the umbilical vein that carried well-oxygenated and nutrientrich blood from the placenta to the fetus
• Ligamentum venosum of the liver

  Is the fibrous remnant of the fetal ductus venosus that shunted blood from the umbilical vein to the inferior vena cava, short circuiting the liver
• Vessels of the liver

  Receives blood from two sources: The portal vein (70%), The proper hepatic artery (30%)
• Portal vein

  • Drains venous blood from the gastrointestinal tract, spleen, pancreas, and gallbladder to the sinusoids of the liver
  • From sinusoids blood is conveyed to the systemic venous system by the hepatic veins that drain directly to the inferior vena cava
  • Is formed by the union of the superior mesenteric and splenic veins posterior to the neck of the pancreas
  • Collects poorly oxygenated but nutrient-rich blood from the abdominal part of the gastrointestinal tract
  • The main channel of the portal venous system
  • Branches end in expanded capillaries – the venous sinusoids of the liver
• Inferior vena cava (IVC)

  • The largest vein in the body
  • Returns poorly oxygenated nonportal blood from the lower limbs, most of the back, the abdominal walls, the abdominopelvic viscera
  • Begins anterior to the L5 vertebra by the union of the common iliac veins
  • The union occurs approximately 2.5 cm to the right of the median plane, inferior to the bifurcation of the abdominal aorta
  • Ascends on the right side of the bodies of the L3 through L5 vertebrae and on the right psoas major to the right of the abdominal aorta
  • Leaves the abdomen by passing through the caval foramen in the diaphragm to enter the thorax
  • Almost all blood from the digestive tract is collected by the portal system and passes through the hepatic veins to the IVC
• Portal venous system communications with systemic venous system

  • Esophageal veins
  • Rectal veins (inferior and middle)
  • Superficial epigastric veins
  • Retroperitoneal veins
• Specific portal venous system communications with systemic venous system

  • Esophageal veins to the azygos vein through the left gastric vein
  • Rectal veins (inferior and middle) draining into the inferior vena cava and the superior rectal vein continuing as the inferior mesenteric vein
  • Paraumbilical veins anastomosing with superficial epigastric veins
  • Twigs of colic veins anastomosing with retroperitoneal veins
• Portal-systemic anastomoses

  • Are important clinically in the advent of an intrahepatic or extrahepatic portal venous block because of liver disease or physical pressure (tumour)
  • Blood from gastrointestinal tract can still reach the right atrium of the heart through several, alternate routes
  • Blood can flow in a reverse direction to the inferior vena cava because the portal vein and its tributaries have no valves
• Portal hypertension - the esophageal varices

  • Produces enlarged varicose veins at the sites of anastomoses between portal and systemic veins
  • Veins may become so dilated that their walls rupture, resulting in hemorrhage (esophageal varices)
• Portal hypertension - the head of Medusa

  The paraumbilical veins may become varicose and look somewhat like small snakes radiating under the skin around the umbilicus (caput medusae - the head of Medusa)
• Portal hypertension - hemorrhoids

  Are not typically related to the portal hypertension but can occur
• Hepatic artery

  • Caries well- oxygenated blood from the abdominal aorta
  • Is divided into: Common hepatic artery – from celiac trunk to the origin of the gastroduodenal artery
• Use of liver disease

  Blood from gastrointestinal tract can still reach the right atrium of the heart through several, alternate routes
• Physical pressure (tumour)

  Blood from gastrointestinal tract can still reach the right atrium of the heart through several, alternate routes
• Blood can flow in a reverse direction to the inferior vena cava because the portal vein and its tributaries have no valves
• Portal hypertension

  The esophageal varices
• Portal hypertension - the esophageal varices

  • Produces enlarged varicose veins at the sites of anastomoses between portal and systemic veins
  • Veins may become so dilated that their walls rupture, resulting in hemorrhage (esophageal varices)