Lecture 8: GI System Embryology Flashcards
What gradient causes transcription factors to be expressed in different regions of gut tube allowing specification?
RA gradient
What transcription factor specifies the esophagus?
SOX2
What transcription factor specifies the duodenum and pancreas?
PDX1
What transcription factor specifies the small intestine?
CDXC
What transcription factor specifies the large intestine?
CDXA
What initiates the interaction between endoderm and splanchnic mesoderm leading to specification of the gut tube?
Shh
What does the right peritoneal diverticulum give rise to?
The lesser sac
What does the left peritoneal diverticulum give rise to?
The greater sac
Esophageal stenosis, atresia
Narrowed or occluded esophagus due to incomplete recanalization, usually found in lower 1/3
Congenital esophageal hernia
Stomach herniating into esophagus
Barrett’s esophagus
Acid backing up from stomach changes esophageal lining = pre-cancerous condition
Zenker’s diverticulum
Abnormal additional pouch outside of esophagus
Hypertrophic pyloric stenosis
Hypertrophic pyloric sphincter causes passageway to be small; takes a couple weeks to present; food never gets into duodenum so no bile in the bolus during projectile vomiting
Duodenal atresia
Double bubble sign: air in stomach and duodenum; symptom could be projectile vomiting with bile
Duplication cyst
Tubular structure with internal lining of gastrointestinal epithelium, smooth muscle in wall and adherence to alimentary tract
Extrahepatic biliary atresia
Incomplete canalization of the bile duct; causes jaundice, dark urine, pale stool; surgical correction or transplant needed
What transcription factor induces cells secreting insulin, somatostatin, and pancreatic polypeptide?
PAX4
What transcription factor induces cells secreting glucagon?
PAX6
Annular pancreas
Ventral and dorsal pancreatic buds form a ring around duodenum which presents as duodenal obstruction
Accessory or ectopic pancreatic tissue
Misexpression of PDX1 leads to ectopic expression of pancreas
Malrotation of midgut
Abnormally positioned viscera - increased risk of entrapment of portions of intestine; many negative symptoms; most severely septic shock and necrosis of tissue
Volvulus
Abnormal twisting of intestine causing obstruction; bloat in dogs
Bilious emesis
Green color of bile in emesis; signals obstruction of GI tract below bile duct
Situs inversus due to bowel malrotation
Can lead to intestinal ischemia
Omphalocele
Herniation of abdominal contents through enlarged umbilical ring; midgut loop fails to return to abdominal cavity - enclosed in pale, shiny membranous sac
Gastroschisis
Failure of anterior abdominal wall musculature to close during folding; gut contents NOT surrounded by membrane
Ileal/Meckel’s diverticulum
Failure of vitelline duct to close; can be symptomatic or asymptomatic; rule of 2’s; can cause fistula and fecal discharge through umbilicus
Umbilical hernia
Gut pushes skin and fascia out of umbilicus
Hirschsprung’s disease
Congenital aganglionic megacolon - motor disorder of colon that causes functional intestinal obstruction; failure of migration of neural crest cells that form colonic ganglion cells
What are the results of rotation in the gut tube?
- Changes size of 2 original peritoneal cavities
- Changes anatomical relationships of organs
- Causes changes/loss in some of dorsal mesenteries
Primarily retroperitoneal organ
Developed outside abdominal cavity which never had a mesentery (such as kidney)
Secondarily retroperitoneal organ
Portions of the gut tube whose mesentery fused with lining periotneum
Intraperiotneal organ
Organs with a mesentery
