Gastrointestinal Anatomy + Blood Supply B&B

Question 1

what are the intraperitoneal structures? (7)

Answer 1

1. stomach
2. appendix
3. liver
4. spleen
5. 1st part of duodenum + jejunum + ileum
6. transverse + sigmoid colon + part of rectum
7. tail of pancreas

Question 2

what are the retroperitoneal structures? (5)

Answer 2

1. aorta + IVC (rupture = retroperitoneal bleed!)
2. kidneys
3. 2nd/3rd portion of duodenum
4. ascending + descending colon + part of rectum
5. head + body of pancreas

Question 3

opening between greater and lesser sac of peritoneal cavity

Answer 3

epiploic foramen (Omental, Winslow’s)

Question 4

where is the pectinate line found?

Answer 4

aka dentate or anocutaneous line: part of anal canal where columnar epithelium (from hindgut) meets stratified squamous epithelium (from ectoderm)

looks like tooth-like projections on imaging

Question 5

contrast the arterial supply, venous supply, lymph drainage, and innervation above and below the pectinate line

Answer 5

part of anal canal where columnar epithelium (from hindgut) meets stratified squamous epithelium (from ectoderm)

above: superior rectal artery (of IMA) + portal system venous drainage (may swell in portal HTN) + internal iliac nodes + visceral innervation (no pain - internal hemorrhoids)

below: inferior rectal artery (of pudendal artery, from iliac) + venous drainage to IVC + superficial inguinal nodes + somatic innervation (painful - external hemorrhoids)

Question 6

what branches off the abdominal aorta? (5)

Answer 6

1. celiac trunk
2. superior mesenteric artery (SMA)
3. renal arteries
4. testicular/ovarian arteries
5. inferior mesenteric artery (IMA)

… then split into common iliac arteries

Question 7

what structures are supplied by the celiac trunk? (7)

Answer 7

celiac trunk supplies foregut:
1. esophagus
2. stomach
3. liver
4. gallbladder
5. spleen
6. part of duodenum
7. part of pancreas

Question 8

what are the 3 main branches of the celiac trunk?

Answer 8

1. common hepatic (R body)
2. splenic (L body)
3. left gastric (travels superiorly)

Question 9

what arteries supply the lesser vs greater curvature of the stomach?

Answer 9

lesser curvature: left gastric (directly off celiac trunk) + right gastric (off proper hepatic, branch of common hepatic)

greater curvature: left gastroepiploic (off splenic artery) + right gastroepiploic (off gastroduodenal artery, branch of common hepatic)

Question 10

gastric ulcers may rupture and cause bleeding from the _____ artery

posterior duodenal ulcers may rupture and cause bleeding form the _____ artery

Answer 10

gastric ulcers may rupture and cause bleeding from the left gastric artery

posterior duodenal ulcers may rupture and cause bleeding form the gastroduodenal artery

Question 11

from where do the short gastric arteries branch, and what part of the stomach do they supply?

Answer 11

short gastric arteries branch from splenic artery and supply the fundus and upper cardiac portions of stomach

important - vulnerable to ischemia if splenic artery is occluded because they lack dual blood supply

Question 12

which part of the stomach is vulnerable to ischemia because there is NO dual blood supply?

Answer 12

short gastric arteries branch from splenic artery and supply the fundus and upper cardiac portions of stomach - NO dual blood supply, vulnerable to ischemia

Question 13

what is contained in the hepatoduodenal ligament? (3)

Answer 13

1. proper hepatic artery (branch of common hepatic)
2. portal vein
3. common bile duct

Question 14

what is the clinical use of Pringle’s maneuver?

Answer 14

Pringle’s maneuver = clamping the hepatoduodenal ligament during surgery to control liver bleeding

hepatoduodenal ligament contains proper hepatic artery + portal vein + common bile duct

if this maneuver DOES NOT control liver bleeding, bleeding comes from IVC or hepatic vein

Question 15

which structures are supplied by the superior mesenteric artery (SMA)? (7)

Answer 15

SMA supplies midgut:
1. distal duodenum
2. jejunum
3. ileum
4. cecum
5. appendix
6. ascending colon
7. first 2/3 of transverse colon

Question 16

what branches off the superior mesenteric artery (SMA) on the R vs L side of body?

Answer 16

right side of body branches: middle colic, right colic, ileocolic arteries

left side of body branches: ileal and jejunal arteries which form an arcades (anastomoses) [+ vasa recta arteries extending from arcades]

Question 17

what is the cause of SMA syndrome?

Answer 17

SMA (superior mesenteric artery) courses over the distal 1/3 of duodenum and may cause bowel obstruction

duodenum pressed between SMA and aorta, classically in a patient with recent massive weight loss (fat pad shrinks)

Question 18

what structures are supplied by the inferior mesenteric artery (IMA)? (3)

Answer 18

IMA supplies hindgut:
1. last 1/3 of transverse colon]
2. descending colon
3. sigmoid colon

Question 19

where is there an abdominal collateral between the celiac trunk and SMA?

Answer 19

superior pancreaticoduodenal (celiac branch) + inferior pancreaticoduodenal (SMA branch)

therefore, gastric ischemia due to vessel occlusion is very unlikely

Question 20

where is there an abdominal collateral between the SMA and IMA?

Answer 20

Marginal artery of Drummond receives branches from middle (SMA) and left (IMA) colic arteries - courses along transverse and descending colon

can become ischemic due to shock, but very unlikely from vessel occlusion

Question 21

where is there an abdominal collateral between the IMA and iliac artery?

Answer 21

superior rectal artery (from IMA) + middle rectal artery (from iliac artery)

therefore, rectal ischemia from occlusion is very unlikely

Question 22

name 3 places in the abdomen where collateral circulation makes ischemia from vessel occlusion highly unlikely?

Answer 22

1. stomach: superior pancreaticoduodenal (celiac trunk) + inferior pancreaticoduodenal (SMA)
2. Marginal artery of Drummond: branches from middle (SMA) and left (IMA) colic arteries
3. rectum: superior rectal artery (IMA) + middle rectal artery (iliac artery)

Question 23

mesenteric ischemia vs ischemic colitis

Answer 23

mesenteric ischemia = ischemia of intestines, that of small intestine is most severe, often life threatening

ischemic colitis = ischemia of colon, may spontaneously resolve, less severe

Question 24

what are the 2 watershed areas of the colon that are most at risk for ischemia in shock or hypo-perfusion?

Answer 24

1. splenic flexure: supplied by smallest branches of marginal artery of Drummond (furthest from SMA or IMA)
2. rectosigmoid junction: supplied by narrow branches of IMA

pt at risk = ICU patients with hypotension or on pressors