Hindgut

Question 0

What structure serves as the nerve supply to the midgut?

Answer 0

Superior mesenteric plexus

Question 1

What major aortic branch supplies the midgut?

Answer 1

Superior mesenteric artery

Question 2

What GI structures is the midgut comprised of?

Answer 2

1. Duodenum (second two segments)
2. Jejunum
3. Ileum
4. Cecum
5. Appendix
6. Ascending colon
7. Transverse colon

Question 3

What major aortic branch supplies the Hindgut?

Answer 3

Inferior mesenteric artery

Question 4

What structure serves as the nerve supply for the Hindgut?

Answer 4

Inferior mesenteric plexus

Question 6

What GI structures is the Hindgut comprised of?

Answer 6

1. Descending colon
2. Sigmoid colon
3. Rectum

Question 7

Specify which organs of the hindgut are peritoneal or retroperitoneal.

Answer 7

1. Descending colon: retroperitoneal
2. Sigmoid colon: peritoneal
3. Rectum: retroperitoneal

Question 8

Are tenia coli, epiploic appendages and haustrum present in the descending colon, sigmoid colon and in the rectum?

Answer 8

No, you will only find those three structures in the descending colon and sigmoid colon. `

Question 9

What is the bending or change in direction of the transverse colon near the spleen called?

Answer 9

left colic flexure or splenic flexure

Question 10

List the branches of the inferior mesenteric artery that serve the organs of the hindgut.

Answer 10

1. superior rectal arteries
2. sigmoidal arteries
3. left colic artery

Question 11

There is an anastomoses between the superior mesenteric artery and the inferior mesenteric artery. Which two branches are responsible for this anastomoses?

Answer 11

middle colic artery (from SMA) and the left colic artery (from IMA). Together these two create the marginal artery.

Question 12

Describe one surgical instance where the midgut would be supplied with IMA blood and the hindgut would be supplied with SMA blood.

Answer 12

1. aortic aneurysm repair or stenting might result in the removal of the IMA. Thus the marginal artery would supply the hindgut with SMA blood.
2. If the transverse colon is resected as a part of a hemicolectomy, the middle colic artery might be removed. If this occurs, the marginal artery will supply portions of the midgut with blood from the IMA.

Question 13

What larger vein does the inferior mesenteric vein join?

Answer 13

It joins the splenic vein, which joins the SMA to become the portal vein. Thus, a large amount of blood from the midgut and hindgut ends up in the liver.

Question 14

The inferior mesenteric plexus is a visceral plexus. What types of fibers would we find in it?

Answer 14

1. motor: (parasympathetic and sympathetic)

2. sensory

Question 15

Where are the cell bodies of the parasympathetic fibers that we would find in the inferior mesenteric plexus?

Answer 15

They are not in the midbrain, because they are NOT vagal fibers! The parasympathetic fibers of the hindgut have cell bodies in the sacral spinal cord (S2-S4). These are the pelvic splanchnic parasympathetic nerves.

Question 16

List two ways parasympathetic axons of the sacral flow can reach their targets.

Answer 16

1. travel with the ventral rami of spinal nerves S2-S4

2. take off from the spinal cord on their own and find their own way to target organs.