Block 6 Anatomy Periton Cav Intest Umich W Expl
Questions and Answers
- 1.
Which of the following veins does not run a course parallel to the artery of the same name?
- A.
Superior epigastric
- B.
Superficial circumflex iliac
- C.
Inferior mesenteric
- D.
Superior rectal
- E.
Ileocolic
Correct Answer
C. Inferior mesentericExplanation
The inferior mesenteric vein and inferior mesenteric artery do not run in tandem. The inferior mesenteric vein is part of the portal venous system--it drains into the splenic vein which drains into the hepatic portal vein. The inferior mesenteric artery is a branch off the descending aorta at the level of the L3 vertebral body. However, the inferior mesenteric artery and vein supply/drain the same region: the descending and sigmoid colon and the rectum.
The superior epigastric vessels run together and are the continuation of the internal thoracic artery and vein. The superficial circumflex iliac vessels run together in the superficial fat of the abdominal wall. The superior rectal vessels are the terminal ends of the inferior mesenteric vessels, found on the superior surface of the rectum. The ileocolic artery and vein are branches off the superior mesenteric vessels. They are both running in the mesentery, supplying/draining the cecum, appendix, and terminal portion of the ileum.Rate this question:
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- 2.
The presence of which feature (also obvious on a radiograph with barium contrast) distinguishes small from large bowel?
- A.
Circular folds of the mucosa
- B.
Circular smooth muscle layer in the wall
- C.
Mucosal glands
- D.
Longitudinal smooth muscle layer in the wall
- E.
Serosa
Correct Answer
A. Circular folds of the mucosaExplanation
The small intestine features circular folds of tissue that are covered with villi - these folds are very obvious on a radiograph with barium contrast. The colon does not have similar folds in the mucosa. Some other things that distinguish the small intestine from the large intestine are: 1) The large intestine has 3 strips of longitudinal muscle, called tenia coli, instead of a continuous longitudinal muscle layer the whole way around. 2) The tenia coli are shorter than the colon, so the colon forms bulges, called haustra. 3) The surface of the colon is covered with fatty omental appendages.
The colon and small intestine share similar circular smooth muscle layers and a serosa. Although the gland structure is different in the colon versus the small intestine, this would not be visible on a radiograph. The same goes for the longitudinal muscle layer - there are differences between the two organs, but not ones that you would see on a barium contrast radiograph.Rate this question:
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- 3.
Occlusion of the inferior mesenteric artery is seldom symptomatic because its territory may be supplied by branches of the:
- A.
Gastroduodenal
- B.
Ileocolic
- C.
Middle colic
- D.
Right colic
- E.
Splenic
Correct Answer
C. Middle colicExplanation
The middle colic artery is the branch from the superior mesenteric artery that supplies the transverse colon. This is the most distal part of the colon that receives blood from the SMA. Branches from the middle colic go to the marginal artery, which would be able to supply the descending colon, sigmoid colon, and rectum if the inferior mesenteric artery was occluded. The ileocolic and right colic arteries are also branches of the SMA supplying the colon (and contributing to the marginal artery), but the middle colic, which serves a more distal part of the colon, is a better answer.
The gastroduodenal artery is a branch off of the common hepatic artery which supplies parts of the duodenum, pancreas, and stomach. The splenic artery is one of the three branches of the celiac trunk. It supplies the spleen, pancreas, and curvature of the stomach.Rate this question:
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- 4.
During exploratory abdominal surgery on a 55-year-old male complaining of right lower quadrant pain, the surgeon initially sees no appendix but knows that he can quickly locate it by
- A.
Looking at the confluence of the teniae coli
- B.
Palpating the ileocecal valve and looking just above it
- C.
Following the course of the right colic artery
- D.
Removing the right layer of the mesentery of the jejunoileum
- E.
Palpating and inspecting the pelvic brim
Correct Answer
A. Looking at the confluence of the teniae coliExplanation
The teniae coli are three bands of longitudinal muscle on the surface of the large intestine. Remember, the large intestine does not have a continuous layer of longitudinal muscle - instead, it has teniae coli. These three bands meet at the appendix, which is the terminal portion of the cecum. The appendix is below the ileocecal valve, not above it. It is not near the right colic artery, which supplies the ascending colon. The appendix would not be found by removing a layer of the mesentery of the jejunoileum - in fact, the appendix has its own mesentery, the mesoappendix. Finally, the appendix is not on the pelvic brim.Rate this question:
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- 5.
During development of the gut:
- A.
The sigmoid colon is retroperitoneal
- B.
The inferior mesenteric artery is the axis for rotation of the midgut loop
- C.
The stomach rotates around its longitudinal axis causing the ventral border to become the greater curvature
- D.
The liver is non-functional
- E.
None of the above
Correct Answer
E. None of the aboveExplanation
None of the statements about development are correct. During development, structures that are peritonealized become retroperitoneal when they are pressed against the body wall and stay there. Structures do not start out retroperitoneal and become peritonealized later. Since the sigmoid colon is peritonealized in the adult, it has not and will not ever be retroperitoneal. The superior mesenteric artery is the axis for rotation of the midgut loop. This should make sense, since the SMA supplies the midgut. When the stomach rotates, the ventral border becomes the lesser curvature. Finally, the liver is functional in the fetus - it is an early site for the formation of erythrocytes.Rate this question:
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- 6.
Meckel's diverticulum:
- A.
Is an abnormal persistance of the urachus
- B.
Is a site of ectopic pancreatic tissue
- C.
Is caused by a failure of the midgut loop to return to the abdominal cavity
- D.
Is an abnormal connection of the midgut to the duodenum
- E.
Is associated with polyhydramnios
Correct Answer
B. Is a site of ectopic pancreatic tissueExplanation
Meckel's diverticulum is an out-pouching of the small bowel that is present in 2% of the people and usually occurs about 2 feet before the junction with the cecum. It can be lined by the mucosa of the stomach and ulcerate. Or, it can be lined with ectopic pancreatic tissue. An abnormal persistence of the urachus is called a urachal fistula. Since the urachus is attached to the bladder, this can be detected if yellow fluid (urine) is seen coming from the umbilicus of a newborn. A failure of the midgut loop to return to the abdominal cavity is called an omphalocele. In this instance, the midgut remains in the body stalk, where it had left the gut to rotate. Polyhydramnios is an excess production of amniotic fluid , often caused by anencephaly or an esophageal fistula.
The other conditions will be covered more in embryology - for now, focus on Meckel's diverticulum.Rate this question:
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- 7.
Visceral pain is often referred to a site on the body wall (where the patient "feels" it) that is innervated by the same spinal cord segment that innervates the visceral organ involved. Pain of appendicitis is often first felt around the umbilicus, indicating that the appendix receives its sympathetic (and thus visceral afferents) from which spinal cord segment?
- A.
T 9
- B.
T 10
- C.
T 11
- D.
T 12
- E.
L 1
Correct Answer
B. T 10Explanation
Sensation from around the umbilicus is mediated by T10. This is an important landmark to rememberRate this question:
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- 8.
A surgical maneuver which takes advantage of the avascular plane of fusion fascia can be applied to mobilize all of the organs below, except the:
- A.
Ascending colon
- B.
Descending colon
- C.
Duodenum
- D.
Kidney
- E.
Pancreas
Correct Answer
D. KidneyExplanation
Fusion fascia forms when an organ becomes secondarily retroperitoneal. Secondarily retroperitoneal organs started out in a mesentery, but then got pushed against the posterior body wall during development. So, the peritoneal covering on the face of these organs which was pushed against the posterior body wall became fusion fascia--a relatively avascular plane of fascia that holds these organs to the posterior body wall. The ascending colon, descending colon, duodenum, and pancreas are all secondarily retroperitoneal organs which are attached by fusion fascia. The kidney is an entirely retroperitoneal organ that was never associated with a mesentery during development. So, it is not attached to the body wall by fusion fascia.Rate this question:
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- 9.
A surgeon performing an appendectomy was unable to identify the base of the appendix due to massive adhesions in the peritoneal cavity. Eventually she identified the cecum and was able to localize the base of the appendix. What anatomical structure(s) on the cecum would she have used to find the base of the appendix?
- A.
Omental appendages
- B.
Haustra coli
- C.
Ileal orifice
- D.
Semilunar folds
- E.
Teniae coli
Correct Answer
E. Teniae coliExplanation
The teniae coli are three bands of longitudinal muscle on the surface of the large intestine. The large intestine does not have a continuous layer of longitudinal muscle--instead, it has teniae coli. These three bands meet at the appendix, which projects from the dependent portion of the cecum. The omental appendages are fatty appendages which are unique to the large intestine. These are all over the large intestine and are not specifically associated with the appendix. The haustra are multiple pouches in the wall of the large intestine, which form where the longitudinal muscle layer of the wall of the large intestine is deficient. Remember--the teniae coli, omental appendages, and the haustra are the three distinctive features of the large intestine!
The ileal orifice is the space where the ileum open into the cecum--it is surrounded by the ileocecal valve. The semilunar folds are the folds found along the lining of the large intestineRate this question:
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- 10.
The spleen normally does not descend below the costal margin. However, it pushes downward and medially when pathologically enlarged. What structure limits the straight vertical downward movement?
- A.
Left colic flexure
- B.
Left suprarenal gland
- C.
Ligament of Treitz
- D.
Pancreas
- E.
Stomach
Correct Answer
A. Left colic flexureExplanation
The left colic flexure, also called the splenic flexure, is the point where the colon takes a sharp downward turn. This flexure is the point where the transverse colon ends and the descending colon begins. It is located immediately inferior to the spleen, so an enlarged spleen must move medially to avoid this colic flexure. The left suprarenal gland is a retroperitoneal structure which sits superior to the kidney. The suspensory muscle of the duodenum or ligament of Treitz is a thin sheet of muscle derived from the right crus of the diaphragm--it suspends the fourth part of the duodenum from the posterior abdominal wall. Both the pancreas and stomach lie medial to the speen. These organs would not prevent the spleen from descending inferiorly.Rate this question:
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- 11.
During the surgical repair of a hiatal hernia, the celiac branch of the posterior vagal trunk was severed accidentally. The damage to this nerve would affect the muscular movements, as well as some secretory activities, of the gastrointestinal tract (GI). Which segment is least likely to be affected by the nerve damage?
- A.
Ascending colon
- B.
Cecum
- C.
Jejunum
- D.
Ileum
- E.
Sigmoid colon
Correct Answer
E. Sigmoid colonExplanation
The vagus nerve supplies parasympathetic fibers to all of the abdominal organs which receive blood from the celiac trunk or superior mesenteric artery. This means that the vagus supplies parasympathetics to the entire GI tract, up to the last part of the transverse colon. The end of transverse colon and all GI structures distal to that point receive parasympathetic innervation from the pelvic splanchnic nerves and blood from the inferior mesenteric artery. So, the ascending colon, cecum, jejunum, and ileum would all be affected by damage to the vagus nerve. The sigmoid colon, which receives parasympathetic innervation from the pelvic splanchnics, would not be affected.Rate this question:
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- 12.
A 70-year-old man with cancer of the ascending colon was admitted to the hospital for tumor removal. The surgeon may perform any of these surgical procedures EXCEPT:
- A.
An incision in the left lower quadrant to access the tumor.
- B.
Examination of the superior mesenteric lymph nodes for possible metastasis.
- C.
Ligation of the relevant branches of the superior mesenteric artery.
- D.
Mobilization of the concerned intestinal segment by freeing its fusion fascia.
- E.
Protect the peritoneum from possible fecal contamination.
Correct Answer
A. An incision in the left lower quadrant to access the tumor.Explanation
The ascending colon is on the right side of the abdomen--the surgeon would not need to explore the left lower quadrant! Because the ascending colon is supplied by the superior mesenteric artery, the surgeon might need to ligate branches of this artery, and the surgeon would also want to check the superior mesenteric nodes for metastasis. Since the ascending colon is secondarily retroperitoneal, it can be mobilized by freeing its fusion fascia. Finally, it's always a good idea to protect the peritoneum from fecal contamination!Rate this question:
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- 13.
A 60-year-old woman arrived at the emergency room complaining of acute abdominal pain. She was diagnosed with ischemic bowel resulting from an obstruction of one or more branches of the inferior mesenteric artery. Which of the following is most likely NOT to be seriously affected by the ischemia?
- A.
Cecum
- B.
Descending colon
- C.
Rectum
- D.
Sigmoid colon
- E.
Splenic flexure
Correct Answer
A. CecumExplanation
The inferior mesenteric artery supplies blood to the end of the transverse colon and all distal structures in the GI tract. This means that the splenic flexure, descending colon, sigmoid colon, and rectum would all be deprived of blood if the inferior mesenteric artery was occluded. The cecum receives blood from the superior mesenteric artery, so it would not be affected by the obstructionRate this question:
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- 14.
A surgeon has decided to perform a segmental resection of the descending colon on a 70-year-old man with intestinal cancer. In principle, any of these surgical procedures might be necessary EXCEPT:
- A.
An extended left lower quadrant incision to approach the descending colon.
- B.
Examining the sacral lymph nodes for possible enlargement.
- C.
Ligation of the relevant left colic artery branches.
- D.
Mobilizing the concerned intestinal segment by freeing its fusion fascia.
- E.
Protecting the peritoneum from possible fecal contamination.
Correct Answer
B. Examining the sacral lymph nodes for possible enlargement.Explanation
The descending colon drains into the inferior mesenteric nodes--these are the lymph nodes that the surgeon would want to check for enlargement, not the sacral nodes. The descending colon can be approached from the lower left quadrant. It is a secondarily retroperitoneal organ, so it can be mobilized by freeing fusion fascia. It would also be important to ligate branches of the left colic artery, since this is the branch of the inferior mesenteric that supplies the descending colon. And, obviously, the peritoneum should be protected from fecal contamination!Rate this question:
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- 15.
As the bowel is exposed, the surgeon says in amazement, "This is a loop of large bowel!" Which characteristic(s) would identify it specifically as large bowel?
- A.
A serosa
- B.
Circular folds
- C.
Epiploic appendages
- D.
Tenia
- E.
C and D
Correct Answer
E. C and DExplanation
There are three features that distinguish the large intestine from the small intestines. The large intestine does not have a continuous longitudinal muscle layer--instead, it has three strips of longitudinal muscle known as teniae coli. The large intestine is covered with omental appendages, which are fat-filled pendants of peritoneum on the surface of the large intestine. Finally, the large intestine is folded into sacculations known as haustra, which form where the longitudinal muscle layer of the wall of the large intestine is deficient.
Serosa is a general term for the outermost coat or serous layer of a visceral structure that lies in the body cavities of the abdomen or thorax. Circular folds are found in the small intestine, and semilunar (sometimes called semicircular) folds are found in the large intestine. These folds are actually much more prominent in the small intestine; in the large intestine, there are mostly semicircular folds which do not continue around the entire intestineRate this question:
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- 16.
The anastomotic artery running along the border of the large intestine is called the:
- A.
Arcade
- B.
Arteriae rectae
- C.
Coronary
- D.
Ileocolic
- E.
Marginal
Correct Answer
E. MarginalExplanation
The marginal artery is an important anastomosis for the large intestine. It runs around the border of the large intestine, and it is formed by the anastomosis of branches of the ileocolic artery, right colic artery, middle colic artery, left colic artery, and sigmoid artery. If a small artery becomes occluded, these branches allow blood to reach all segments of the colon. Arcades are anastomotic loops between arteries that provide alternative pathways for blood flow. These arcades are more prominent in the small intestine than the large intestine. Arteriae rectae (straight arteries) are the small branches that run from the marginal artery to reach the colon. The ileocolic artery is the branch of the superior mesenteric artery that supplies the cecum, appendix, and terminal portion of the ileum. The coronary arteries supply blood to the heart, but just to confuse things, the gastric veins are refered to as coronary veins, because they crown the lesser curvature of the stomach.Rate this question:
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- 17.
The inferior mesenteric artery is often occluded by atherosclerosis without symptoms; its normal area of distribution therefore must be supplied by collateral blood flow between which arteries?
- A.
Ileocolic and right colic
- B.
Left and middle colic
- C.
Left colic and sigmoidal
- D.
Right and middle colic
- E.
Sigmoidal and superior rectal
Correct Answer
B. Left and middle colicExplanation
To answer this question, you need to identify which branches represent an anastomosis between the superior mesenteric artery and the inferior mesenteric artery. So, you want to find the answer choice listing the most distal branch of the superior mesenteric artery and the most proximal branch of the inferior mesenteric artery. And, those branches are the middle colic (from the SMA) and the left colic (from the IMA).
The ileocolic, right colic, and middle colic arteries are branches of the superior mesenteric artery; the left colic, sigmoidal, and superior rectal arteries are branches of the inferior mesenteric artery.Rate this question:
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- 18.
The artery of the midgut is the:
- A.
Celiac trunk
- B.
Inferior mesenteric
- C.
Proper hepatic
- D.
Splenic
- E.
Superior mesenteric
Correct Answer
E. Superior mesentericExplanation
The superior mesenteric artery is the artery of the midgut. The celiac trunk is the artery of the foregut, and the inferior mesenteric arery is the artery of the hindgut. The splenic artery is a branch of the celiac artery, and the proper hepatic artery is a branch of the common hepatic artery, which is a branch of the celiac artery.Rate this question:
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