Embryology foregut

Question 1

When is the primitive gut tube formed?

Answer 1

During embryo folding

Question 2

Where does the epithelia of the gut tube originate from?

Answer 2

Endoderm

Question 3

Where does the smooth muscle and connective tissue of the gut tube originate from?

Answer 3

Visceral mesoderm

Question 4

Where do the visceral and parietal peritoneum originate from?

Answer 4

Visceral and parietal mesoderm

Question 5

How is the gut tube attached to the posterior abdominal wall?

Answer 5

Suspended by dorsal mesentery

Question 6

How much of the gut tube does the dorsal msentery suspend?

Answer 6

Lower oesophagus to cloaca

Question 7

How much of the gut tube does the ventral mesentery suspend?

Answer 7

Lower oesophagus to first part of duodenum (forms lesser omentum)

Question 8

From what structure do the arteries supplying the gut originate?

Answer 8

The vitelline arteries

Question 9

What occurs from week 6-9 in formation of the gut tube?

Answer 9

Recanalisation- epithelial cells proliferate and occlude the gut, over the next 2 weeks apoptosis of this creates vacuoles. By week 9 the tube is fully recanalised. During this the epithelia differentiate further

Question 10

What three problems can occur with recanalisation?

Answer 10

1. Duplication
2. Stenosis
3. Atresia

Question 11

How does the oesophagus develop?

Answer 11

Separated form the respiratory diverticulum by the trancheoesophageal septum in week 4.

Question 12

What additional type of muscle does the oesophagus have? Where from?

Answer 12

Skeletal muscle from the paraxial mesoderm.

Question 13

What problems can occur with oesophageal development?

Answer 13

1. Tracheoesophageal fistula
2. Oesophageal atresia (results in polyhydramnios)
3. Congenital hiatal hernia

Question 14

How can you tell the difference between a congenital and an acquired hiatal hernia?

Answer 14

Congenital is irreducible

Question 15

How does the stomach develop?

Answer 15

Week 4- dilation of foregut
Week 5- Differential growth forms the greater and lesser curvatures
Week 7-8- rotation 90 degrees clockwise around the craniocaudal axis, and rotation in the ventrocaudal axis also so the greater curvature faces slightly caudally.

Question 16

Where is the greater curvature positioned before and after craniocaudal rotation?

Answer 16

Before- dorsal, after- left

Question 17

What happens to the vagus nerves during rotation of the stomach?

Answer 17

Rotate from left and right to ventral and dorsal. Left vagus trunk is ventral, right is dorsal

Question 18

How is the lesser sac created?

Answer 18

Craniocaudal rotation of the stomach- space behind it.

Question 19

How is the greater omentum developed?

Answer 19

Dorsal mesentery attached to greater curvature and posterior abdominal wall.
It continues to grow and reflects back on itself to form an extension of the lesser sac.
Before birth the ventral and dorsal folds, and the mesentery of the transverse colon, fuse.

Question 20

What is congenital pyloric stenosis?

Answer 20

Hypertrophy of the smooth muscle = narrowing of the pyloric sphincter. 5x more common in males. Restricts emptying.
Results in dilation of the stomach, projectile vomiting, a palpable mass and visible peristalsis.

Question 21

What is heterotopic gastric tissue?

Answer 21

Innapropriate epithelial differentiation of gut tube - ectopic gastric tissue.
Acid production in random places leads to inflammation and ulceration.
Can result in stricutres due to scarring.

Question 22

How is the duodenum developed?

Answer 22

In week 4 the gut tube elongates to a ventrally projecting C shape. Dragged to the right by the rotating stomach. The dorsal mesentery of the duodenum degenerates causing it to be secondarily retroperitoneal.

Question 23

Where are the proximal and distal halves of the duodenum from?

Answer 23

Proximal from foregut, distal from the midgut