Embryology Flashcards
Where does the foregut extend from?
Esophagus to ampulla of vater (2nd part of duodenum)
Where does the midgut extend from?
Lower duodenum to proximal 2/3s of transverse colon
Where does the hindgut extend from?
Distal 1/3 of transverse colon to anal canal above the pectinate line
During what week of development does the midgut herniate through the umbilical ring?
6th
During what week of development does the midgut return to the abdominal cavity?
10th
How does the midgut rotate when returning back into the abdominal cavity?
270° counterclockwise (also rotates around SMA)
Name 2 extremely common ventral wall defects
- Gastroschisis
- Omphalocele
What ventral wall defect is associated with chromosomal abnormalities (e.g trisomy 13, 18 and Beckwith-Wiedemann)
Omphalocele
What is the main difference between Gastroschisis and Omphalocele?
- Gastroschisis - guts not covered peritoneum or amnion
- Omphalocele - Gut contents covered by peritoneum and amnion (gray shiny sac)
What is the etiology of gastroschisis?
Abdominal contents extrude through abdominal folds (typically right of umbilicus)
What is the etiology of Omphalocele?
Failure of lateral walls to migrate at umbilical ring
- Causes persistant midline herniation of abdominal contents into umbilical cord
What is the cause of a congenital umbilical hernia?
Failure of the umbilical ring to close after physiological herniation of the midgut.
- May get worse with crying (increased intra-abdo pressure)
- Small defects close spontaneously
- May be associated with congenital disorders
What is the most common tracheoesophageal anomaly?
Esophageal atresia with distal tracheoesophageal fistula (85%)
How does esophageal atresia with TEF usually present?
- In utero - polyhydramnios (inability of fetus to swallow amniotic fluid)
- Neonates drool, choke, vomit within 1st feeding
- Cyanosis due to laryngospasm (avoid refluc-related aspiration)
What clinical test can diagnose esophageal atresia (with TEF)?
Failure to pass nasogastric tube into stomach
In pure esophageal atresia what does CXR show?
Gasless abdomen
- Unlike pure TEF, or EA with TEF where there will be a prominent gastric bubble
What does pure TEF (transesophageal fistula) show?
- H-type fistula
- Can see a prominent gastric bubble
What are the 3 types of tracheoesophageal anomaly?
- Pure esophageal atresia
- Pure tracheoesophageal fistula
- Esophageal atresia with distal transesophageal fistula
What do intestinal atresias present with?
Bilious vomiting and abdominal distension within first 1-2 days of life
What can be seen on imaging of duodenal atresia?
- Double bubble on X-ray (dilated stomach, proximal duodenum
What syndrome may be associated with duodenal atresia?
Down syndrome
What are the severe complications of jejunal and ileal atresia?
- Disruption of mesenteric vessels (typically SMA)
- Causes ischemic necrosis of fetal intestine
- > Segmental resorption: bowel becomes discontinuous
What may be seen on imaging in jejunal and ileal atresia?
- Triple bubble (dilated stomach, duodenum, proxima jejunum)
- Gasless colon
What is the most common cause of gastric outlet obstruction in infants?
Hypertrophic pyloric stenosis
What are the features of hypertrophic pyloric stenosis?
- Palpable olive-shaped mass in epigastric region (visible peristaltic waves)
- Nonbilious projectile vomiting at 2-6 weeks
Wha does imaging show in hypertrophic pyloric stenosis?
US shows thickened and lengthened pylorus
What metabolic disorder is caused by pyloric stenosis?
Hypokalemic hypochloremic metabolic alkalosis (secondary to vomitting of gastric acid)
What may predispose to hypertrophic pyloric stenosis?
Macrolide exposure (also more common in firstborn males)
What is the treatment of hypertrophic pyloric stenosis?
Surgical incision of pyloric muscles (pyloromyotomy)
What is an Annular pancreas?
Abnormal rotation of ventral pancreatic bud forms a ring of pancreatic tissue -> encircles 2nd part of duodenum, may cause duodenal narrowing and vomiting
What does the ventral pancreatic bud form?
- Uncinate process
- Main pancreatic duct
- Pancreatic head (partly)
What does the dorsal pancreatic bud form?
- Body
- Tail
- Isthmus
- Accessory duct
- Part of pancreatic head
What is pancreas divisum?
- Ventral and dorsal parts of the pancreas fail to fuse at 7 weeks of development.
- Common and often asymptomatic
- May cause chronic abdo pain and/or pancreatitis
