GI EMBRYOLOGY Flashcards
Which germ layer does the GI tract come from?
Endoderm
Which key structures bud off from foregut in embryonic development?
Lungs
What is function of tracheo-oesophageal septum?
What will happen if there is abnormal development of this structure?
Divides lung buds from oesophagus
Abnormal development leads to oesophageal atresia i.e. closed oesophagus. This occurs when septum deviates posteriorly
What is most common form of oesophageal atresia?
Oesophageal atresia with tracheo-oesophageal fistula
Why is there polyhydramnios in oesophageal atresia?
Baby cannot swallow amniotic fluid
In a newborn baby who is drooling and choking and has reflux - air in the stomach on chest x-ray indicates what condition?
how is it treated?
Oesophageal atresia with distal tracheo-oesophageal fistula
→ surgical repair
What is this condition? Explain how it forms?
Omphalocele
at week 6, abdomen temporarily becomes too small causing intestine to herniate through umbilical cord. This is physiological and reduction occurs by week 12. If it does not, it causes an omphalocele (protrusion of intestines through umbilicus covered by peritoneum)
What are omphaloceles often associated with?
Genetic defects e.g. down syndrome, Edward syndrome
What is this condition? How is it differentiated from another similar midgut congenital abnormality?
Gastroschisis
Protrusion of bowel through abdominal wall
► Differentiated from emphalocele as it protrudes through wall defect not umbilical cord, and is not covered by peritoneum
What is the difference between gastroschisis and omphalocele in terms of:
- genetic defects?
- GI function?
Genetic defects: Rare in gastroschisis, common in omphaloceles
GI function: Poor in gastroschisis, normal in omphalocele
What three things can malrotation of the midgut cause?
- Obstruction
- Volvulus
- Left-sided colon
What is the vitelline duct?
what happens to it normally?
Connection between yolk sac and midgut
normally disappears by week 9
What is the most common congenital abnormality of the GI tract?
how is it diagnosed?
Meckel’s diverticulum: incomplete obliteration of vitelline tube
often asymptomatic
► Diagnosis: Technetium-99m Scan → detects gastric mucosa; 50% of symptomatic MD have ectopic gastric or pancreatic cells. This is displayed as a spot on scan distant from stomach. In children scan is highly accurate, in adults not as much
Why might a Meckel’s diverticulum cause ulceration of adjacent ilieum?
Some contain embryonic remnants of gastric tissue and secrete acid
What is the rule of twos for Meckel’s diverticulum?
- 2% prevalence
- 2:1 male:female ratio for symptomatic presentations
- most commonly 2 feet (60 cm) proximal to ileocaecal valve in adults
- 2 types of ectopic tissue (gastric and pancreatic)
- commonly 2 inches (5 cm) long
- one half of symptomatic are younger than 2 yrs
Where in the GI tract is the most common place for babies to have atresia or stenosis? List some symptoms they may present with
Duodenum
Polyhydramnios in utero
Bilious vomiting
Which genetic abnormality is duodenal atresia associated with?
What radiological feature indicates this DA?
Down syndrome
Double bubble sign: distension of duodenum stump + stomach with tight pylorus in middle
Projectile, non-bilious vomiting in a 3 week old baby is most likely which condition?
on abdominal exam of a baby with this condition what are you likely to feel?
Pyloric stenosis caused by hypertrophy of the pylorus
palpable mass which feels like an olive
What is unusual about the origin of the spleen when comparing to the rest of the GI tract?
Arises from mesoderm not endoderm
