Embryology foregut Flashcards
When is the primitive gut tube formed?
During embryo folding
Where does the epithelia of the gut tube originate from?
Endoderm
Where does the smooth muscle and connective tissue of the gut tube originate from?
Visceral mesoderm
Where do the visceral and parietal peritoneum originate from?
Visceral and parietal mesoderm
How is the gut tube attached to the posterior abdominal wall?
Suspended by dorsal mesentery
How much of the gut tube does the dorsal msentery suspend?
Lower oesophagus to cloaca
How much of the gut tube does the ventral mesentery suspend?
Lower oesophagus to first part of duodenum (forms lesser omentum)
From what structure do the arteries supplying the gut originate?
The vitelline arteries
What occurs from week 6-9 in formation of the gut tube?
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
What three problems can occur with recanalisation?
- Duplication
- Stenosis
- Atresia
How does the oesophagus develop?
Separated form the respiratory diverticulum by the trancheoesophageal septum in week 4.
What additional type of muscle does the oesophagus have? Where from?
Skeletal muscle from the paraxial mesoderm.
What problems can occur with oesophageal development?
- Tracheoesophageal fistula
- Oesophageal atresia (results in polyhydramnios)
- Congenital hiatal hernia
How can you tell the difference between a congenital and an acquired hiatal hernia?
Congenital is irreducible
How does the stomach develop?
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.
Where is the greater curvature positioned before and after craniocaudal rotation?
Before- dorsal, after- left
What happens to the vagus nerves during rotation of the stomach?
Rotate from left and right to ventral and dorsal. Left vagus trunk is ventral, right is dorsal
How is the lesser sac created?
Craniocaudal rotation of the stomach- space behind it.
How is the greater omentum developed?
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.
What is congenital pyloric stenosis?
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.
What is heterotopic gastric tissue?
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.
How is the duodenum developed?
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.
Where are the proximal and distal halves of the duodenum from?
Proximal from foregut, distal from the midgut
