FOCUS QUESTIONS and ANSWERS

 

1. Name and define the nine regions of the anterior abdominal wall, list the importance of each.

• right hypochondriac: liver and gall bladder
• epigastric: pain from heartburn, ulcer
• left hypochondriac: spleen tenderness
• right lumbar (flank): ascending colon, kidney
• umbilical: visceral pain often refers here
• left lumbar (flank): descending colon, kidney
• right inguinal: appendix
• hypogastric (pubic, suprapubic): bladder and rectum
• left inguinal: gas pain

 

 

 

 

2. Differentiate between the abdominal cavity and the peritoneal cavity.

 

The peritoneal cavity is within the abdominal cavity, which is continuous with the pelvic cavity. The peritoneal cavity is a potential space, like the pleural and pericardial cavities, between the parietal and visceral layers of the peritoneum. It allows the gut to move with a minimum of friction.

 

 

 

3. What is the suspensory ligament of the duodenum?

 

The suspensory ligament of the duodenum (also known as the suspensory muscle of the duodenum or the Ligament of Treitz) is the structure that suspends the duodenojejunal flexure from the diaphragm. It meets the right crus of the diaphragm at the esophageal hiatus (T10 level).

 

 

 

4. Locate the ileocecal junction. At what level is it found?

 

The ileocecal junction is just posterior to the anterior superior iliac spine, in the iliac fossa, which is at L4-L5. Another way to say that is that it is right on or just inferior to the transtubercular line, in the right inguinal region.

 

 

 

5. Examine the mesentery of the small intestine (of the jejunum and ileum), noting its body wall attachment. How long is this attachment? What structures does it cross? 

 

The root of the mesentery is approximately 15cm long. It passes inferiorly and to the right, from the duodenaljejunal junction to the iliocecal junction, crossing:

·         ascending and horizontal parts of the duodenum

·         abdominal aorta

·         inferior vena cava

·         right ureter

·         right psoas major muscle

·         right testicular or ovarian vessels

 

6. What is the location of the small intestine within the peritoneal cavity?

 

Most of the jejunum is located in the left upper quadrant, while the ileum is mostly in the right lower quadrant.

 

 

 

7. What parts of the large intestine are peritoneal. What parts are retroperitoneal?

 

The ascending and descending colon are retroperitoneal. The cecum, transverse colon and the sigmoid colon are peritoneal, and are suspended by mesenteries.

 

 

 

8. Consider the derivation of the anterior cecal fold (vascular), the ileocecal fold, the mesoappendix, the transverse mesocolon, and the sigmoid mesocolon with regard to gut development.

 

Much like "the mesentery", these structures are derived from the primitive dorsal mesentery. Again, the gut rotates and some structures, like the ascending and descending colon, become retroperitoneal. The remaining intraperitoneal structures; the cecum, appendix, transverse colon, and sigmoid colon; are attached to the body wall via the anterior cecal fold (vascular) and ileocecal fold, the mesoappendix, the transverse mesocolon, and the sigmoid mesocolon respectively.

 

 

 

9. Why are some parts peritoneal or retroperitoneal?

 

As gut development proceeds some parts get squished against the posterior body wall and stick there.

 

 

 

10. What happens to the primitive mesentery of the retroperitoneal part of the large intestine?

 

The mesentery belonging to the parts that are squished against the wall becomes fused with the peritoneal lining of the wall, and is now called "fusion fascia".

 

 

 

11. What is the significance of fusion fascia?

 

Fusion fascia is a relatively avascular connective tissue plane through which nerves and vessels pass, usually parallel to its plane, to reach target structures. The clinical significance is that it allows retroperitoneal structures to be mobilized during surgery (as long as blunt dissection is performed, so that vessels and nerves are not sectioned). Very small veins may traverse across the plane of the fusion fascia. These so-called "veins of Retzius" may enlarge in cases of portal hypertension.

 

 

 

12. Where does the superior mesenteric artery terminate?

 

The ileocolic artery is the terminal branch of the superior mesenteric artery. It supplies the structures near the ileocecal junction.

 

 

 

13. Describe the superior mesenteric vein and its branches.

 

Starting superior and moving inferiorly, the tributaries of the SMV are the gastroduodenal vein, the anterior and posterior inferior pancreatoduodenal veins, the middle colic vein and the right colic vein. Areas drained include the ileocecal junction, the ascending and transverse colon, the duodenum, the pancreas, and the greater curvature of the stomach. Behind the neck of the pancreas, the SMV unites with the splenic vein to form the portal vein.

 

 

 

14. Is there a separate ascending branch of the left colic artery accompanying the inferior mesenteric vein?

 

The left colic artery usually splits into an ascending and a descending branch. Because the inferior mesenteric vein travels more superiorly to drain to the splenic vein, it is often accompanied for part of its course superiorly by the ascending branch of the left colic artery as this artery travels toward the splenic flexure.

 

 

 

15. Examine the arteriae rectae of the large intestine. How do they differ from those of the small intestine?

 

The arteriae rectae of the large intestine are quite long, are fairly large in caliber, and are branches of the marginal artery. On the other hand, the arteriae rectae of the small intestine are shorter, smaller, and are branches of the arterial arcades of the small intestine.

 

 

 

16. What constitutes the marginal artery?

 

The marginal artery is the anastomosis of branches of the ileocolic, right colic, middle colic, left colic, and sigmoid arteries. It forms a collateral circulatory circuit for the large intestine.

 

 

 

17. Define the omental bursa (lesser sac). How does it develop? What is its entrance? What are its boundaries?

 

The omental bursa is a space that exists between the stomach and the posterior wall of the abdominal cavity. It gives the stomach room to expand after a meal. It is created by the rotation of the stomach during development so that the greater curvature faces left (and inferiorly) and the lesser curvature faces right (and superiorly). The growth of the liver helps to define the borders of the omental bursa. Your fingers can be stuck into the space through the omental foramen. The boundaries of the omental bursa are as follows:

·         superior: caudate lobe of liver

·         ventral: the stomach

·         posteriorly: posterior abdominal wall

·         inferior: the duodenum

 

 

18. 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? 

 

Yes, the right gastric anastomoses with the left.

 

 

19. Does the left gastro-omental artery anastomose with the right? 

 

Yes.

 

20. How does the splenic artery reach the spleen? How do its branches reach the stomach? (Note relations to stomach, kidney and left colic (splenic) flexure.)

 

The course of the splenic artery from the celiac trunk to the spleen is very tortuous. Along the way, it is partially embedded in the superior part of the pancreas, and therefore more or less runs in the floor of the omental bursa. It passes through the splenorenal ligament, dividing into several branches to supply the spleen. Near its end, the splenic artery gives off the left gastro-omental artery, which supplies the greater curvature of the stomach and anastomoses with the right gastro-omental artery. It also gives off four or five short gastric branches, which supply some blood to the fundus of the stomach. They anastomose with both the left gastric and the left gastro-omental arteries.

 

 

21. Look for a hepatic branch of the anterior vagal trunk 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?

 

The anterior vagal trunk sends branches to the stomach and liver, usually with an extension of this hepatic branch going down to the duodenum. The posterior vagal trunk also branches to stomach, but has no hepatic branch. It also branches to the celiac ganglion.

 

 

22. How do sympathetic branches distribute to the stomach?

 

It is provided from T5-T9 via the greater thoracic splanchnic nerve, to the celiac ganglion and plexus.

 

 

23. Is the superior (1st) part of the duodenum peritoneal or retroperitoneal?

 

Both. The first 2 cm has a mesentery, the hepatoduodenal ligament. The rest of the superior part of the duodenum is retroperitoneal.

 

 

 

24. What is the suspensory muscle of the duodenum?

 

The suspensory muscle of the duodenum (also known as the ligament of Trietz) is a thin sheet of muscle fibers derived from the right crus of the diaphragm that suspends the fourth part of the duodenum (the duodenojejunal flexure or junction) from the posterior abdominal wall.

 

 

25. What is the relation of the horizontal (3rd) part of the duodenum to the superior and inferior mesenteric arteries?

 

The 3rd part of the duodenum is crossed anteriorly by the SMA and vein. It is superior to the IMA.

 

 

26. Carefully trace the common 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?

 

The posterior superior pancreaticoduodenal artery from the gastroduodenal artery passes anterior to the duct as it passes to the right, then travels inferiorly posterior to the common bile duct.

 

 

27. How does the posterior arcade differ from the anterior arcade?

 

The posterior arcade is further away from the duodenum, so its vasa recta to the duodenum must be longer.

 

 

28. Do you find veins with the arterial arcades of the pancreas and duodenum?

 

The respective veins travel with the arteries of the duodenum and pancreas. They drain to the superior mesenteric vein and/or the portal vein.

 

 

29. Does the splenic vein receive the inferior mesenteric vein?

 

The splenic vein receives the inferior mesenteric vein in slightly more than a third of individuals, while inferior mesenteric vein first unites with superior mesenteric vein in approximately one third of individuals. In the remaining individuals (slightly less than a third), the three veins unite at the same point to form the portal vein.

 

 

30. Into which part of the duodenum do the common bile and pancreatic ducts open?

 

The descending (2nd) part of the duodenum.

 

 

31. Where are the cystic veins?

 

Small cystic veins pass from the gallbladder into the liver through the bed of the gallbladder. There is an anterior and posterior branch.

 

 

32. What are the fetal functions of the round ligament of the liver (ligamentum teres hepatis, a remnant of the obliterated umbilical vein), and the ligamentum venosum?

 

The round ligament of the liver was the umbilical vein that carried well-oxygenated and nutrient rich blood from the placenta to the fetus. The ligamentum venosum is the fibrous remnant of the fetal ductus venosus that shunted blood from the umbilical vein to the IVC, short-circuiting the liver before birth.

 

 

33. Identify the hepatic veins. How many are there?

 

Hepatic veins are formed by the union of the central veins of the liver and open into the IVC just inferior to the diaphragm. There are three: left, right and middle hepatic veins.

 

 

34. Did you find any hepatic lymph nodes?

 

The superficial lymphatics can be found in the subperitoneal fibrous capsule of the liver.

 

 

35. Review all of the tributaries of the portal vein and completely organize its drainage pattern. What organs does it drain?

 

The portal vein collects low oxygen, high nutrient blood from the GI tract and spleen.

 

 

36. Where are the postganglionic neurons of the suprarenal glands located?

 

The suprarenal medulla is directly innervated by preganglionic sympathetic fibers, causing a systemic sympathetic response. (The suprarenal (adrenal) medulla is modified nerve tissue. Activation of it causes the release of norepinephrine and/or epinephrine, which enter the blood stream and cause the systemic response.) However, postganglionic neurons from the celiac ganglion reach the cortical tissue of the suprarenal glands to innervate the suprarenal blood vessels.

 

 

 

37. What is the significance of the location of the celiac branches of the posterior vagal trunk as they join the celiac plexus?

The significance of this branch of the vagus is that it distributes to the organs supplied by the celiac and superior mesenteric arteries.

 

 

38. Is there a superior mesenteric ganglion around the superior mesenteric artery?

Yes, but it is often fused with the celiac ganglia.

 

 

39. Is there an inferior mesenteric plexus or ganglia around the inferior mesenteric artery?

Yes, but the ganglion may be small or indistinguishable.

 

 

40. How does the thoracic sympathetic trunk get into the abdomen?

The sympathetic trunk passes beneath the medial arcuate ligament on each side.