Embryology of the Midgut and Hindgut

Question 1

What is the gut derived from?

Answer 1

Endoderm and Visceral Mesoderm

Question 2

What does the visceral mesoderm give rise to?

Answer 2

Visceral Peritoneum
Muscle Wall
CT for the wall, pancreas and liver

Question 3

What does the endoderm give rise to?

Answer 3

Epithelium of bowel
Hepatocytes of Liver
Endo and Exocrine cells of the pancreas

Question 4

What is the nerve supply for each part of the gut supplied by?

Answer 4

Ganglia of sympathetic chain

Question 5

What is vasculature and innervation of midgut and hindgut?

Answer 5

M: Lesser and SMA
H: IMA and Least (T12 and L1)

Question 6

What do the dorsal and ventral mesenteries become?

Answer 6

D: Greater Omentum
V: Lesser Omentum

Question 7

What are the 5 stages of midgut development?

Answer 7

1) Elongation
2) Herniation
3) Rotation
4) Retraction
5) Fixation

Question 8

What happens in elongation?

Answer 8

1) Rapid elongation forms primary intestinal loop

2) Proximal part of loop forms the SI and distal forms large intestine (2/3 TC)

Question 9

What happens in herniation?

Answer 9

Rapid growth causes loop to be pushed into extra embryonic cavity in umbilical cord during week 6

Question 10

What happens in rotation?

Answer 10

Elongated intestinal loop rotates 270 deg AC (Causes jejunum and ileum to form lots of coiled loops)

Question 11

What happens in retraction?

Answer 11

In week 10, herniated midgut returns into expanded abdominal cavity (jejunum returns first)

Question 12

What happens in fixation?

Answer 12

Some regions of gut lose dorsal mesentery becoming retroperitoneal

Question 13

What are the fixed parts?

Answer 13

Duodenum, ascending and descending colon and rectum

Question 14

What are the mobile parts?

Answer 14

Stomach, jejunum, ileum, appendix, caecum, transverse and sigmoid colons