Lab Manual - Duodenum, Pancreas, Liver, & Gallbladder

Learning Objectives:

Upon completion of this session, the student will be able to:

  1. Identify and describe the parts and peritoneal relationships of the duodenum and pancreas. (explanation)
  2. Describe the pattern of common vasculature of the duodenum and pancreas. (explanation)
  3. Trace the potential collateral blood flow between celiac and superior mesenteric arterial territories, and between superior and inferior mesenteric arterial territories. (explanation)
  4. Trace the pathway of common entry of the bile ducts and pancreatic ducts into the 2nd part of the duodenum. (explanation)
  5. Identify parts of the liver and describe the relationships of its portal venous, hepatic arterial, and hepatic venous circulation. (explanation)
  6. Identify the structures passing into and out of the porta hepatis and some of the most common variations on this pattern. (explanation)
  7. Describe the peritoneal relationships of the liver and gallbladder. (explanation)
  8. Explain the discrepancy between the external lobulation of the liver and the true internal segmentation of the liver based on the branching of the intrahepatic arteries, veins, and ducts. (explanation)

Readings and Modules:

Procedure:

1. Expose the duodenum and pancreas and define their parts. (Play movie; View images: N 268, 270A, 270B, 272, 273, 274, 279, 298, 310, 301, 304, 306, 329, TG 5-14, 5-18, 5-19, 5-26A, 5-26B, 5-26C, 5-27B, 5-27C)

Review the development of the duodenum and pancreas. Determine the manner in which they become secondarily retroperitoneal and fixed by the attachments of the transverse mesocolon and the mesentery.

Review, with the aid of your atlas, the structures that are retroperitoneal and overlain by the pancreas and duodenum (aorta, inferior vena cava, kidneys, ureters, portal vein, etc.).

If not done previously, cut through the attachment of the gastrocolic ligament to the transverse colon (preserving the gastro-omental arteries along the greater curavture of the stomach) and turn the stomach up, exposing the posterior wall of the omental bursa. Trace the attachment of the transverse mesocolon across the duodenum and pancreas. Note which parts of the pancreas and duodenum constitute boundaries of the omental bursa and which parts are below or outside. Locate the tail of the pancreas and note that it and the splenic artery and vein are within the splenorenal (lienorenal) ligament. Note the manner in which the mesentery attaches to the fourth (ascending) part of the duodenum. Observe how this placement allows the superior mesenteric artery and vein to enter the root of the mesentery after crossing the third part of the duodenum.

Remove these mesenteric attachments and clear the surface of the duodenum and pancreas.

Duodenum. Observe the 4 subdivisions of the duodenum, their vertebral levels, the peritoneal and visceral relations of each. Is the first part peritoneal or retroperitoneal? Why? What is the suspensory muscle of the duodenum (ligament of Treitz)? Identify the retroduodenal fossa and paraduodenal fold. Find the inferior mesenteric vein within the paraduodenal fold. What is the relation of the third part of the duodenum to the superior and inferior mesenteric arteries?

Duodenum

Pancreas. Identify uncinate process, head, neck, body and tail, and review position and visceral relations. Specifically note relations to celiac trunk, superior mesenteric artery and vein, splenic artery and vein, and the bile duct.

Pancreatic cancer

The vasculature of the pancreas and duodenum is so arranged that it may be considered common to both. Arteries are derived from the celiac trunk, the superior mesenteric artery, and arcades formed between. The vessels are delicate. Dissect with care. Locate and trace the gastroduodenal artery. Continue tracing to its branching into the right gastro-omental and the anterior superior pancreaticoduodenal artery. Note that it lies between the duodenum and pancreas. Passing deep to a part of the head of the pancreas it becomes continuous with the anterior inferior pancreaticoduodenal artery. Trace the latter to the common stem, the inferior pancreaticoduodenal from the superior mesenteric artery. This completes the anterior arcade. Examine the arteriae rectae off the arcade.

2. Incise the peritoneum at the right border of the duodenum and reflect it medially. Identify the arterial supply to the pancreas and duodenum. (Play movie; View images: N 294, 301, 304A, 304B, 306, 309, 311, 312, TG 5-24, 5-26, 5-27B, 5-27C, 5-28)

Now incise the peritoneum along the right border of the second part of the duodenum. Reflect the duodenum and pancreas toward the mid-line in the plane of the fusion fascia (explain). Carefully trace the bile duct as it courses behind the first part of the duodenum and the head of the pancreas to the medial wall of the second part of the duodenum. Does an artery cross it? This artery is usually the first branch from the gastroduodenal artery and is the posterior superior pancreaticoduodenal. Trace to its source and then across the bile duct and head of the pancreas to become continuous with the posterior inferior pancreaticoduodenal. Trace to its source. How does this posterior arcade differ from the anterior?

Locate the splenic artery as it leaves the celiac trunk. Trace along the pancreas, noting multiple small pancreatic and, in the region of the tail, small caudal pancreatic branches. A large branch near the beginning of the splenic artery, the dorsal pancreatic artery, passes dorsal to the pancreas, continues to the inferior border of the pancreas and divides into 1) a left branch (the inferior pancreatic artery) and 2) a right branch (which crosses ventral to the head to unite with a left branch of the anterior superior pancreaticoduodenal artery as the prepancreatic arcade). Do you find veins with the arteries?

3. Trace the splenic vein to its junction with the superior mesenteric vein and the formation of the portal vein. (Play movie; View images: N 266, 311, 312, 313, 314, 315, TG 5-27, 5-28, 5-35A, 5-35B, 5-37)

Trace the splenic vein; note relations to splenic artery and pancreas. Does it receive the inferior mesenteric vein? Note junction with superior mesenteric vein and the point of formation of the portal vein.

CT of pancreas Portal venous system

Look for lymph nodes: pyloric, pancreaticosplenic, celiac and hepatic and consider lymph drainage. Organize with the lymph drainage of the stomach.

4. Incise the duodenum and examine its interior including the papillae and folds. (Play movie; View images: N 276, 279, 279, 273, 288, 294, 295, 310, 304, 315, 319, 320, 322, 331, TG 5-19A, 5-19B, 5-24B, 5-24C, 5-26, 5-27, 5-35, 5-42)

Cut open the duodenum in its first and second parts. Observe the pyloric sphincter, the smooth first part, and the circular folds of the second. Locate the greater duodenal papilla, a visible protrusion of the mucosa on the posteromedial wall of the descending part of the duodenum. Do you find a lesser duodenal papilla? Differences?

Lift the first and second parts of the duodenum and associated pancreas to the left and trace the bile duct caudally to the dorsal side of the pancreas and to its termination in the duodenum (which part? ). Explore the termination of the bile duct and the main pancreatic duct in the greater duodenal papilla. These two ducts may open independently on the papilla, but they often unite within the duodenal wall to form a dilation called the hepatopancreatic ampulla (of Vater) (within the papilla). Note nerve plexus and lymph nodes along the structures of the hepatoduodenal ligament. Examine the portal vein and epiploic foramen. Where is the inferior vena cava?

5. Expose pancreatic ducts on the posterior aspect of the pancreas. (Play movie; View images: N 279, 279, 294, 298, 301, 304A, 304B, TG 5-24, 5-26, 5-27B, 5-27C)

On the posterior aspect of the head of the pancreas, follow the bile duct to the wall of the duodenum. From this point, dissect away pancreatic tissue to find the main pancreatic duct and follow it into the body of the pancreas. Note that it lies closer to the dorsal than to the ventral surface of the pancreas. Do you have an accessory pancreatic duct? A large pancreatic artery that arises from the splenic artery and enters the pancreas, accompanying the pancreatic duct, is the great pancreatic artery.

6. Examine the liver, gallbladder and biliary system, defining their peritoneal relations and parts. (Play movie; View images: N 229, 238, , 256, 265, 275, 286, 287A, 287B, 288, 289, 288, 291, 292, 294, 294, 310, 301, 306, 310, 312, 313, 315, 348, 331, 399, TG 5-02, 5-18, 5-19, 5-21A, 5-21B, 5-21C, 5-23, 5-24A, 5-24B, 5-24C, 2-25, 5-27, 5-28, 5-34, 5-35, 5-42)

Review the development of the ventral mesogastrium and determine the relationships of the liver within it. Define the falciform ligament, the coronary ligament and the right and left triangular ligaments. Review the relationship of the lesser omentum and its parts to the liver.

Observe the surface projection of the liver, its relation to the thorax, costal margin, diaphragm, lungs, heart, posterior body wall, and viscera of the abdominal cavity.

Consider the anterior body wall projection of the fundus, body and neck of the gallbladder and their peritoneal relations to the liver. Note the relationships to the first part of the duodenum and to the transverse colon. Strip the remaining peritoneum from the hepatoduodenal ligament. Locate the bile duct and trace to the porta hepatis. Identify the cystic duct, common hepatic and right and left hepatic ducts. Trace the proper hepatic artery toward the porta. Identify right and left hepatic arteries and the cystic artery. Note the relation of the right hepatic artery to the common hepatic duct. Variations are very common in this region; the most common pattern probably occurs less than half the time. If you detect variations from the common descriptions, trace the arteries to their sources (aberrant hepatic arteries). Where are the cystic veins? To clarify the arrangement of structures of the hepatic pedicle, cut the peritoneum around the gallbladder and pull the gallbladder from its fossa on the right lobe of the liver.

Surface projection of abdominal organs Gallstones
CT of liver and gall bladder Gallstones
Cholangiogram showing biliary system    

Incise the falciform ligament and coronary ligaments to reflect the liver forward. Cut the inferior vena cava between the diaphragm and the liver. Examine the diaphragmatic surface of the liver, determining the extent and attachments of the coronary ligament. Find the bare area. On the visceral surface distinguish lobes and fissures and the attachment of the lesser omentum. Note that the lesser omentum is continuous with the coronary and falciform ligaments.

Complete the dissection of portal structures if not previously done. Note that branches of the portal vein, hepatic artery and bile duct always travel together. Follow the portal vein to the porta, identifying the right and left branches. On the left branch identify the transverse and umbilical parts, the round ligament of the liver (ligamentum teres hepatis - a remnant of the obliterated umbilical vein), and the ligamentum venosum. What are the fetal functions of the latter two structures? Identify the hepatic veins; how many are there? Read about the lymphatic drainage of the liver. Did you find any hepatic lymph nodes?

Review all of the tributaries of the portal vein and completely organize its drainage pattern. What organs does it drain? Consider the major sites of anastomoses between the portal system and the systemic (caval) veins, or portacaval anastomoses: esophageal veins, superior rectal veins, paraumbilical veins, posterior body wall (retroperitoneal) veins. These connections may be small and difficult to find if they have not been used to shunt blood from the portal to the caval veins. But they often become quite enlarged in cases of portal hypertension.

Venogram of the portal vein

Read about the basic segmentation of the liver and the intrahepatic distribution of branches of the portal vein, hepatic ducts, and hepatic arteries. Is there any relationship between this intrahepatic pattern and the division of the liver into right and left lobes based on external appearance?

 

Updated: 11January 2012