GI embryology Flashcards
What are the derivatives of the forgut?
Pharynx, esophagus, stomach, lower resp tract, duodenum (1st and 2nd parts), liver, billary tree and pancreas.
What is the order or regions in the embryonic tube?
Pharynx, esophageal, gastric and duodenal, liver.
How does the esophagus separate from the respiratory tract?
The tracheoesophageal septum divides the pharynx into esophagus and respiratory bud which will form the lungs.
What are the parts of the esophagus made of?
Upper 1/3rd has a striated muscle external layer.
Lower 1/3rd is smooth muscle.
From what does the upper 1/3rd of the esophagus develop?
The mesenchyme of the 4th and 6th pharyngeal arches.
From what does the lower 1/3rd of the esophagus develop?
The surrounding splachnic mesenchyme.
What is the innervation of the esophagus?
Vagus.
When does the stomach first begin to develop?
4th wk at which the tube dilates to form the primordial stomach.
How does the primordial stomach develop?
From the 4th to 6th week it broadens, this occurs faster on the dorsal surface forming the greater curvature.
Where does the stomach develop in?
The dorsal mesentry.
What occurs at week 5?
The stomach rotates by 90 degrees.
Where does the lesser sac form and why?
Posterior to the stomach due to rotation.
Why does the stomach rotate?
Because of its own growth and the growth of the liver.
From what does the liver and billary tree develop form?
The hepatic diverticulum of the forgut.
What occurs to the hepatic diverticulum as the gut grows?
The connection elongates and narrows into the bile duct.
What structures develop from the hepatic diverticulum?
Liver, gall bladder, bile duct and ventral pancreatic duct.
Where does the hepatic diverticulum develop?
In the ventral mesentry.
Where does the pancreas develop from?
It develops in 2 buds-
Ventral pancreatic bud from hepatic diverticulum
Dorsal pancreatic bud from endoderm of the duodenum.
What occurs during pancreatic development to the two buds?
The ventral pancreatic duct rotates and fuses with the dorsal pancreatic duct. Superior mesenteric vessels get sandwiched between the two layers.
From what is the spleen formed?
The spleen is formed from the dorsal mesogastrium not the gut tube.
When does the spleen develop?
The 4th week due to condensation of the mesenchyme of the lesser sac.
From what does the kidney and bladder develop?
The cloaca in the hind gut.
What is the gut formed from?
The endoderm.
What is the first stage of intestine formation?
Wk 5-6 rapid elongation of gut tube bellow stomach forming primary intestinal loop.
