Embryology of the Foregut

Question 1

what supplies and innervates the foregut

Answer 1

Foregut is supplied by the coeliac trunk and its branches and innervated by the greater splanchnic nerve T6-9 running through sympathetic chain

Question 2

the foregut has 2 mesenteries

Answer 2

dorsal mesentery (greater omentum), ventral mesentery (lesser omentum and ligaments of liver)
in foregut there is a mesentery going from bowel to the anterior abdominal wall (lesser omentum in which liver grows) forms falciform ligament and ligamentum teres which runs in free edge of ventral mesentery to liver

Question 3

development of the buds

Answer 3

4 buds growing out of the bowel wall into the mesenteries
2 of the buds develop into the biliary system and the liver and they fuse quite quickly with the duodenum by one connection – the common bile duct
Pancreas forms from 2 buds, one bud goes anteriorly towards the anterior part of the abdomen and the other part goes posteriorly into the dorsal mesentery (greater omentum
As the liver develops is stretches the ventral mesentery, so there is a gap where the mesentery doesn’t attach to the anterior abdominal wall (bare area of the liver)
There is a second pancreas (dorsal pancreas) growing out towards the spine

Question 4

rotation due to liver and pancreas

Answer 4

As liver grows it wont fit in this space so it rotates round into the left side of the abdomen, rotates bowl round in doing so and pulls both pancreases with it
now the pancreas causes rotation as it wants to lie horizontally so this part of the bowel grows rapidly until the pancreases come to lie next to each other on the posterior lateral side of the duodenum

the 2 pancreases then fuse together and layers of peritoneum in that area fuse together , quite often there is an accessory pancreatic duct

Question 5

rotation of the stomach

Answer 5

Liver moves right and spleen left, rotating stomach
Liver gains connection with inferior vena cava and this fuses
Liver enlarges and fuses with posterior wall

Question 6

summary

Answer 6

• The foregut has a dorsal and ventral mesentery.
• The liver develops in the ventral mesentery and the spleen develops in the dorsal mesentery.
• The pancreas develops as a ventral and dorsal part which rotate posteriorly and fuse together.
• The stomach rotates and its dorsal edge elongates to form the greater curve.
• Fixation of the greater omentum and liver to the posterior wall creates a space behind the stomach; the lesser sac.