4.2 Development of the Midgut and Hindgut

Question 1

What occurs in physiological herniation?

Answer 1

The growing midgut and liver cannot both fit in the abdominal cavity so the intestinal loop herniates into the umbilical cord

Question 2

Describe midgut rotation

Answer 2

The midgut rotates 90 degrees anticlockwise when herniated

It then turns another 180 degrees as it reenters the abdominal cavity.

Question 3

How does the cecal bud form?

Answer 3

The cranial limp of the primary intestinal loop reenters the cavity first and moves to the left. Once inside the cecal bud drops to form the ascending colon

Question 4

What does the cranial limb of the primary intestinal loop become?

Answer 4

Distal duodenum, jejunum, proximal ileum

Question 5

What does the caudal limb of the primary intestinal loop become?

Answer 5

Distal ileum, cecum, appendix, ascending colon, proximal 2/3rd of descending colon

Question 6

What happens if the midgut only rotates 90 degrees?

Answer 6

The colon is on the left hand side

Question 7

What happens if the midgut rotates in the opposite direction 90 degrees?

Answer 7

The transverse colon passes posterior to the duodenum

Question 8

What is a volvulus of the bowel?

Answer 8

Twisting or compression of the bowel which results in strangulation and ischaemia.

Question 9

What is a vitelline cyst?

Answer 9

The vitelline duct forms fibrous strands with the patent middle section

Question 10

What is a vitelline fistula?

Answer 10

Direct communication between the umbilicus and the intestinal tract

Question 11

What is Meckel’s diverticulum?

Answer 11

A small diverticulum of the bowel
2 feet from ileocecal valve, 2 inches long, detected in under 2s, 2:1 ration in men to women
Can contain ectopic pancreatic or gastric tissue which becomes inflamed.

Question 12

What is recanalisation?

Answer 12

In growth, some structures close due to the rapid growth. Recanalisation is the reopening of these structures

Question 13

What are the two consequences of failed recanalisation?

Answer 13

Atresia- complete failure to open

Stenosis- narrow lumen

Question 14

What is pyloric stenosis?

Answer 14

Hypertrophy of the circular muscle around the pyloric sphincter. Characterised by projectile vomiting

Question 15

What is gastroschisis?

Answer 15

Failure of closure of the abdominal wall during embryo folding which leaves the gut tube outside of the body

Question 16

What is omphalocoele?

Answer 16

Persistance of physiological herniation so the gut is outside the body but covered in a layer of amnion

Question 17

What is the cloaca?

Answer 17

The end part of the hindgut and the urinary tract

Question 18

Above the pectinate line:

i. ) What is the blood supply?
ii. ) What type of epithelia is present?

Answer 18

i. ) Inferior mesenteric artery

ii. ) Columnar

Question 19

Below the pectinate line:

i. ) What is the blood supply?
ii. ) What type of epithelia is present?

Answer 19

i. ) pudendan artery

ii. ) Stratified

Question 20

How does sensation alter on either side of the pectinate line in the anus?

Answer 20

Above the line the only sensation that can be felt is stretch. Below the line, the tissue is sensitive to temperature, touch and pain.

Question 21

What is an imperforate anus?

Answer 21

Failure of anal membrane to perforate

Question 22

What is anal/anorectal agenesis?

Answer 22

Anus does not form

Question 23

What is a hindgut fistula?

Answer 23

An abnormal connection between the hindgut and the bladder

Question 24

Where is viceral pain of the foregut felt?

Answer 24

Epigastrum

Question 25

Where is viceral pain of the midgut felt?

Answer 25

Periumbilical

Question 26

Where is viceral pain of the hindgut felt?

Answer 26

Suprapubic

Question 27

What is the primary intestinal loop?

Answer 27

The midgut elongates rapidly so forms a loop around the superior mesenteric artery