Lab Manual - Stomach & Spleen

Learning Objectives:

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

  1. Identify the parts of the stomach and describe its spatial relationships to surrounding organs and mesenteries. (explanation)
  2. Describe the blood supply of the abdominal foregut via branches of the celiac artery, and the basic pattern of lymphatic drainage in this region. (explanation)
  3. Describe the anatomy of the foregut peritoneal ligaments, omenta and omental bursa, and their development from the embryological ventral and dorsal mesogastria. (explanation)
  4. Describe the pattern of parasympathetic innervation of the GI tract. (explanation)

Readings and Modules:

Procedure:

1. Remove the costal arch from the anterior aspect of the diaphragm. (Play movie; View images: N 266, 276, TG 5-01, 5-18)

Because the rigid lower ribs (except 11 and 12) overlap the liver and other foregut structures anterolaterally, it is advisable to cut and remove them before attempting detailed inspection of this region. Along the same vertical line of incision used to cut through the upper 6 ribs, now cut through ribs 7-10. Remove them completely, being careful not to damage the diaphragm as you detach it from the deep surface of the rib cage.

2. Examine the omental bursa and the derivatives of the dorsal and ventral mesogastria. (Play movie; View images: N 271, 277, 272, 273, 275, 331, 348, TG 5-12A, 5-12B, 5-18A, 5-18B, 5-42)

Study the development of the peritoneum of the upper abdominal viscera. The adult derivative of the ventral mesogastrium is the lesser omentum, composed of hepatogastric and hepatoduodenal ligaments. Note the right free border of the hepatoduodenal ligament, and locate the omental (epiploic) foramen behind it. Put your finger in the omental (epiploic) foramen and explore.

The adult derivative of the dorsal mesogastrium is the greater omentum, composed of the gastrosplenic ligament, gastrocolic ligament, omental apron and splenorenal ligament. Examine how the greater omentum has combined with and assists in the formation of the transverse mesocolon.

Define the omental bursa (lesser sac). How does it develop? What is its entrance? Boundaries? Lift up the transverse colon and cut through the remaining layer of peritoneum of the transverse mesocolon and explore the omental bursa from below, locating the stomach, spleen, pancreas, and posterior body wall peritoneum. In subsequent dissections add to this list of boundaries as you expose other areas.

3. Identify the parts of the stomach and expose the celiac artery. (Play movie; View images: N 232, 272, 274, 275, 276, 277 TG 4-37, 5-18, 5-19, 5-26, 5-34)

Stomach. Examine and define parts: cardia, fundus, body, pyloric antrum, pylorus. On plastinated specimens, observe its ventral wall and observe the mucosa and gastric rugae. On your cadaver, cut through the pylorus and examine arrangement of the pyloric sphincter. Define the lesser and greater curvatures and the mesenteric attachments. Note the abdominal esophagus passing through the diaphragm and the peritoneum reflecting from the diaphragm onto the esophagus and stomach. Also note the pyloroduodenal junction and its peritoneal relations.

Esophagus Stomach with barium
3D images of esophagus Pyloric ulcer
Pylorus    

4. Expose the branches of the celiac artery and define its branches to the stomach and spleen. (Play movie; View images: N 272, 275, , 300, 301, 309, 312, 319, 348, TG 5-18A, 5-18B, 5-19, 5-27, 5-28)

Cut through the central (hepatogastric) part of the lesser omentum and spread open with your fingers, exposing the cavity of the omental bursa (do not mobilize the right side of the stomach). Identify the left gastric artery within the left gastropancreatic fold. Trace the artery upward to the cardia of the stomach and identify esophageal, gastric, and possibly hepatic branches. Trace as far along the lesser curvature as you can, noting distribution to stomach. Preserve the accompanying left gastric vein. Be careful to preserve the superior portion of the hepatogastric ligament, which contains the hepatic branch of the anterior vagal trunk. Now trace the artery back to its source, the celiac trunk. Locate but do not try to expose completely. In the posterior body wall peritoneum locate the right gastropancreatic fold, open and trace the common hepatic artery to the pyloroduodenal junction. As it divides identify the proper hepatic artery and the gastroduodenal artery. Follow along the proper hepatic artery into the hepatoduodenal ligament until you locate the right gastric artery. Trace it to the lesser curvature of the stomach. Does it anastomose with the left gastric artery? Consider how both of these vessels have entered the lesser omentum from a source (celiac trunk) behind the posterior body wall peritoneum.

CT of celiac artery

Now trace the gastroduodenal artery behind the pyloroduodenal junction, noting that the posterior superior pancreaticoduodenal artery arises from it near its origin. As the gastroduodenal artery emerges from below the duodenum, it divides into anterior superior pancreaticoduodenal and right gastro-omental arteries. Trace the right gastro-omental artery through the gastrocolic ligament, noting omental and gastric branches.

Return to the celiac trunk. Note its relation to the superior border of the pancreas. Locate the splenic artery. Lift the stomach and observe the artery lying along the superior border of the pancreas, but do not remove at this time. Note the artery entering the splenorenal ligament and passing to the hilum of the spleen. Return to the stomach and identify the gastrosplenic ligament. As this ligament attaches to the hilum of the spleen locate the splenic artery and its splenic branches, short gastric arteries and the left gastro-omental artery. Trace each of these vessels. Does the left gastro-omental artery anastomose with the right? Locate gastric and omental branches.

5. Examine the spleen, its mesenteric relations and the origin of the portal vein. (Play movie; View images: N 266, 276, 272, 275, 288, , 300, 309, 312, , 315, TG 5-01, 5-18A, 5-18B, 5-19, 5-24, 5-27, 5-28, 5-35A, 5-35B, 5-37)

Mobilize the spleen, note shape, size, relation to ribs and diaphragm. Review gastrosplenic and splenorenal ligaments. How does the splenic artery reach the spleen and its branches reach the stomach? Note relations to stomach, kidney and left colic flexure.

Locate the right gastric vein and trace to the portal vein. In the hepatoduodenal ligament (free border of the lesser omentum), locate the bile duct, the portal vein and the proper hepatic artery. Note their relationship to each other and to the omental foramen. Locate the left gastric vein and trace as far as possible (usually to the portal vein). What is the coronary vein?

Lymphatics. Organize the lymph drainage of the stomach and spleen. Look for paracardial, left gastric, celiac, pyloric, gastroomental, hepatic, and pancreaticosplenic node groups.

6. Expose the branches of the vagal trunks to liver, stomach, and celiac ganglion. (Play movie; View images: N 126, 209, 240, 277, 272, 273, 275, 319, 320, 321, 331, 348, TG 4-45, 5-12, 5-18A, 5-18B, 5-42, 7-92, 8-16, 8-17)

Return to the lesser curvature of the stomach and the left gastric artery. Locate gastric branches of the anterior vagal trunk along the anterior part of the lesser curvature. Trace them back to the esophagus and note relation to esophagus. Look for a hepatic branch passing within the lesser omentum to the liver and then to the duodenum. Do you have an accompanying hepatic branch of the left gastric artery?

On the posterior border of the lesser curvature locate gastric branches of the posterior vagal trunk. Trace to the esophagus, noting relationships. Locate the celiac branch and trace to the celiac plexus. Consider distribution and function of the vagus nerve. How do sympathetic branches distribute to the stomach?

Organize the mesenteries of the stomach, considering their contents and functional importance to the stomach.

 

Updated: 06 January 2012