Anatomy

Question 1

What are the boundaries between the foregut, midgut and hindgut?

Answer 1

Foregut ends at the entrance of bile duct in second part of duodenum.
Midgut ends between proximal 2/3 and distal 1/3 of transverse colon

Question 2

How do all gut structures begin with regards to relationship to mesentery?

Answer 2

They all begin with dorsal mesentery (peritoneal)– Some lose dorsal mesentery to become secondarily retroperitoneal (in midgut/hindgut)

Question 3

What are secondarily retroperitoneal organs? (5)

Answer 3

Duodenum (2nd/3rd parts)
Head/neck/body of pancreas
Ascending colon
Descending colon
Upper rectum

Question 4

What structure is remnant of umbilical vein?

Answer 4

Round ligament of liver

Question 5

What are three constrictions of esophagus?

Answer 5

Cervical (around C6)
Thoracic: Where aortic arch is
Diaphragmatic

Question 6

Describe the muscle breakdown of the esophagus. What is its innervation?

Answer 6

Upper 5%: Voluntary skeletal muscle
Middle 45%: Mixture of skeletal/smooth muscle
Lower 50%: Involuntary smooth muscle

All are innervated by vagus nerve

Question 7

What is the Z line?

Answer 7

Transition between esophageal and stomach epithelium– squamo-columnar junction

Question 8

Name some branches of celiac trunk

Answer 8

Common hepatic artery, gastroduodenal artery (can be eroded by ulcer), Left gastric artery, splenic artery (fundus, greater curvature, pancreas, spleen)

Question 9

What are parts of the duodenum? What is the important landmark?

Answer 9

There are 4 parts of duodenum. The first 1.5 parts are in the foregut– after the entrance of the bile duct, the next 2.5 parts constitute part of the midgut

Question 10

What is the blood supply for the duodenum?

Answer 10

The GDA supplies much of the duodenum as well as the head of the pancreas– there are anterior/posterior superior pancreatic-duodenal arteries
The midgut portions are supplies by the SMA

Question 11

What is the name of the entry for the pancreatic/bile duct?

Answer 11

Major duodenal papilla

Question 12

What is the difference in mucosa between jejunum and ileum?

Answer 12

Ileum is grooved (looks fuzzy on contrast imaging) whereas cecum is smooth

Question 13

What are Peyer’s patches

Answer 13

Big patches of lymphatic tissue

Question 14

What is the difference in blood supply between jejunum and ileum?

Answer 14

Jejunum: Simple arcades, long vasa recta
Ileum: Complex arcades, short vasa recta

Question 15

What are three anatomic features of colon?

Answer 15

Taenia coli: Strips of smooth muscle
Haustrations: Pocket like folds
Epiploic appendages: Little fat things

Question 16

Describe blood supply for colon

Answer 16

Part SMA, part IMA.

SMA: ileocolic artery (ascending colon) with appendiular artery (appendix), middle colic artery ( transverse colon)
IMA: Left colic artery (distal 3rd of transverse and descending), sigmoid arteries (sigmoid colon), superior rectal artery

Question 17

If there were a sudden drop in arterial blood pressure where would you se bowel ischemia? Why?

Answer 17

At the splenic flexure– it’s the transition point between blood supply SMA and IMA

Question 18

What is the difference between the two anal sphincter?

Answer 18

The internal anal sphincter is smooth muscle

External anal sphincter is skeletal muscle under voluntary control (pudendal nerve)

Question 19

How far does vagal innervation go in GI?

Answer 19

End of midgut

Question 20

Where does innervation for handgun come from?

Answer 20

Spinal nerves (pelvic splanchnic nerves) from S2-S4

Question 21

Describe sympathetic innervation for Foregut/midgut and hindgut

Answer 21

Foregut: T5-T9
Midgut: T9-T12
Hindgut: L1-L2

Question 22

How is pain from abdominal viscera carried back to CNS? How is it referred?

Answer 22

It’s carried by sympathetic nerves and is referred to dermatomes of body wall and is poorly localized.