Development of GI System Flashcards
Endoderm gives rise to
Mucosal epithelium and glands except lower 1/3rd of anus
Splanchnic mesoderm gives rise to
Muscular walls, vascular elements and CT elements
Ectoderm gives rise to
Enteric ganglia and nerves/glia (neural crest), epithelium for lower 1/3rd of anus
Dorsal mesentery derivatives
Greater omentum- gastrosplenic, gastrocolic, splenorectal ligaments
Small intestine mesentery
Mesosappendix
Transverse/sigmoid mesocolon
Ventral mesentery derivatives
Lesser omentum- hepatoduodenal/hepatogastric ligaments
Falciform ligament of liver
Coronary ligament of liver
Triangular ligaments of liver
Foregut derivatives
Oral cavity/oropharynx Esophagus Stomach Lungs Liver/gall bladder Pancreas Upper duodenum
Innervation of dorsal/ventral stomach
Left vagus- ventral stomach
Right vagus- dorsal stomach
Hypertrophic pyloric stenosis
Muscularis externa in region hypertrophies forming a mass at the right costal margin
Sphincter cannot relax due to faulty migration of neural crest cells
Vomiting after feeding, fewer stools, failure to gain weight
Liver formation
Begins as diverticulum from gut endoderm that grows into septum transversum
Endoderm differentiates into hepatocytes, bile ducts and hepatic ducts
Liver functions as embryonic hematopoiesis organ
Splanchnic mesoderm contribution to liver
Splanchnic mesoderm differentiates into stromal cells, Kupffer cells and stellate cells
Pancreas formation
Cystic diverticulum and ventral pancreatic buds sprout into ventral mesentery, dorsal bud sprouts into dorsal mesentery
5th week the ventral pancreas migrates around posteriorly and fuses with dorsal pancreas
Dorsal pancreatic duct connection to duodenum is lost as it reconnects to ventral pancreatic duct may be retained as accessory pancreatic duct
Dorsal pancreas forms
Head body and tail of pancreas
Ventral pancreas forms
Uncinate process
Annular pancreas
Pancreatic anomaly causing duodenal obstruction or stenosis
Causing vomiting it annulus develops inferior to bile duct
Pancreatic divisum
Dorsal and ventral pancreatic ducts do not connect
Increases risk of pancreatitis
Biliary atresia
Obliteration of extrahepatic or intrahepatic ducts
Progressive neonatal jaundice soon after birth
White clay colored stool
Dark urine
Midgut derivatives
Lower duodenum Jejunum Ileum Cecum Appendix Ascending colon Proximal 2/3rds of transverse colon
Rotation of midgut
First 90 deg. rotation (50day) brings cecum and future ascending colon into left side
Second 180 deg. rotation (70day) brings cecum to upper right quadrant and ascending colon anterior to duodenum
As midgut returns into cavity (73day) cecum descends to lower right quadrant carrying the ascending colon along with it, so ascending colon ends up along the right side of abdomen
Tail of pancreas is located
Intraperitoneal
Omphalocele
Herniation through umbilicus
Peritoneal covering
Increased risk with trisomy 13 or 18
Usually the intestines retract back into the abdomen before closure- but in this case they do not
Could be caused by lateral folding defecting resulting in weak abdominal wall
Gastrochesis
Herniation through abdominal wall without peritoneal covering
Meckels diverticulum
Failure of yolk stalk (vitelline duct) connection to the midgut to regress
Rules of 2s: 2% incidence, 2x more common in males, 2% have medical symptoms, 2 feet proximal to terminal ileum, 2 inches long, 2 years of age
Can lead to abdominal swelling, intestinal obstruction, bowel sepsis, GI bleed
Non rotation of midgut loop
Does not mean ‘no rotation’
Completes first 90 deg. rotation but not the remaining 180 deg.
Ends up with left sided colon and right sided small intestines
Reverse gut rotation
Completes 90 deg. rotation but then does 180 deg. rotation backwards
Colon ends up on the correct side, but is posterior to the duodenum
