Gastrointestinal embryology

• Foregut: pharynx to duodenum
• Midgut: duodenum to transverse colon
• Hindgut: distal transverse colon to rectum

• Rostral fold closure: sternal defect
• Lateral fold closure: omphalocele, gastroschisis
• Caudal fold closure: bladder exstrophy

• Extrusion of abdominal content through abdominal folds
• NOT covered by peritoneum

• Persistence of herniation of abdominal contents into umbilical cord
• Covered by peritoneum

Omphalocele: covered by peritoneum

• Duadenal atresia: failure to recanalize (trisomy 21)
• Jejunal, ileal, colonic atresia: due to vascular accident (apple peel atresia)

• 6th week: midgut herniates through umbilical ring
• 10th week: returns to abdominal cavity + rotates around SMA

• Malrotation of midgut
• Omphalocele
• Intestinal atresia or stenosis
• Volvulus

Esophageal atresia (EA) with distal tracheoesophageal fistula (TEF) is most common  (85%)

• Sx:
• -drooling, choking, vomiting with first feeding
• -TEF allows air into the stomach (visible on CXR)
• -Cyanosis secondary to laryngospasm (to avoid reflux-related aspiration)

• Clinical test:
• -Filure to pass NG tube into stomach

• Types:
• 

Hypertrophy of the pylorus causes obstruction

• Presentation:
• -Palpable "olive" mass in epigastric region
• -nonbilious projectile vomiting at ~ 2 wks of age
• -1/600 live births; more common in firstborn males

Tx: Surgical incision

• Derived from foregut:
• -Ventral pancreatic bud → pancreatic head, main pancreatic duct; uncinate process
• -Dorsal pancreatic bud → everything else (body, tail, isthmus, accessory pancreatic duct)

• Ventral pancreatic bud abnormally encircles 2nd part of duodenum
• Forms ring of pancreatic tissue → duodenal narrowing

Ventral and dorsal parts fail to fuse at 8 weeks

• Arises in mesentery of stomach (hence is mesodermal)
• Supplied by foregut (celiac artery)