Embryology of the Gastrointestinal Tract Flashcards
What are the derivatives of the foregut?
Supplied by the celiac artery: thyroid lower respiratory tract esophagus stomach proximal portion of duodenum liver gallbladder pancreas
What are the derivatives of the midgut?
Supplied by the superior mesenteric artery: distal portion of duodenum jejunum ileum cecum vermiform appendix ascending colon proximal portion of transverse colon
What are the derivatives of the hindgut?
Supplied by the inferior mesenteric artery: distal portion of transverse colon descending colon sigmoid colon rectum lining of urinary bladder most of anal canal
How does the spleen differentiate?
The spleen develops in the dorsal mesogastrium from splanchnic mesoderm.
How does the stomach differentiate?
Rostral to the hepatic diverticulum (liver bud). Suspended by dorsal mesogastrium. Connected to liver by lesser omentum.
The dorsal surface of the stomach is the _____ curvature.
The dorsal surface of the stomach is the greater curvature. The ventral surface is the lesser curvature.
How is the greater omentum made of 4 layers of splanchnic mesoderm?
The dorsal mesentery of the greater curvature of the stomach folds back on itself and fuses. A mesentery is 2 layers of mesothelium, so the greater omentum is 4 layers.
The key phrase in gut development is:
it rotates clockwise, or to the right, from the embryo’s point of view
From what does the gall bladder develop?
From the hepatic diverticulum
How does the pancreas form?
The ventral pancreatic bud grows out from the hepatic diverticulum.
The dorsal pancreatic bud grows out into the dorsal mesentery.
When the duodenum rotates clockwise, the two lobes of the pancreas fuse on the dorsal side of the gut.
What is an essential phase of midgut development?
Umbilical herniation - liver expands (hematogenesis) so there is no room for midgut (intestines) to develop. It is forced out of the peritoneal cavity through the umbilical ring.
The umbilical herniation makes use of the residual connection between the _____ (space) and ____ (space).
peritoneal cavity and chorionic cavity
What is gastroschisis?
abdominal wall defect - incomplete fusion of transverse folds. Can occur anywhere along the ventral midline of the body.
What is omphalocele?
persistent herniation of the intestines through the unfused body wall, specifically at the umbilicus. The bulging contents are wrapped by amnion!
What is Meckel’s diverticulum?
Persistent connection between the intestines and a remnant of the yolk stalk/vitelline duct. Can range from
ileal diverticulum
fibrous cord
fistula w/ discharge
What 2 things comprise the lesser omentum?
hepatogastric ligament
hepatoduodenal ligament
What is the name of the remaining opening between the lesser and greater sacs?
epiploic foramen
What are the 3 remaining pieces of the original dorsal mesentery?
mesentery proper
transverse mesocolon
mesentery of the sigmoid colon
What is annular pancreas? What does it cause?
The ventral pancreatic bud splits for mysterious reasons, and the 2 ventral buds grow around the duodenum, constricting it.
What is biliary atresia?
failure of the bile duct to recanalize
What is a more common cause (than annular pancreas) of duodenal stenosis/atresia?
Errors in recanalization - first the tube is hollow, then fills, the recanalizes to a hollow tube (needs vascularization to do this). If there is not enough vascularization, then the opening may not form or not form enough.
What can cause projectile vomiting?
congenital hypertrophic pyloric stenosis
What is the ectodermal pit that forms at the cloaca?
proctodeum
What separates the rectum and urogenital sinus?
urorectal septum
