Embryology B&B Flashcards
the digestive tube develops directly from the embryonic…
yolk sac - surrounded by endoderm (GI tract epithelium, glands, organs)
which abdominal organ notably comes from mesoderm, NOT endoderm?
spleen - however, blood supply is celiac trunk (like the stomach)
the foregut is supplied by the ___
the midgut is supplied by the ___
the hindgut is supplied by the ___
the foregut (mouth to Ampulla of Vater) is supplied by the celiac trunk
the midgut (Ampulla of Vater to transverse colon) is supplied by the superior mesenteric artery (SMA)
the hindgut (transverse colon to rectum) is supplied by the inferior mesenteric artery (IMA)
retroperitoneal organs are covered by peritoneum only on the _____ wall and lie against the ______ abdominal wall
retroperitoneal organs are covered by peritoneum only on the anterior wall and lie against the posterior abdominal wall
[they’re squished behind the peritoneum sac]
from what is the ventral mesentery derived, and what remains of it in adults? (2)
derived from septum transversum
liver grows into ventral mesentary, and in adults all that remains is lesser omentum (connects liver and stomach) and falciform ligament (connects liver and anterior abdominal wall)
from what is the greater vs lesser omentum derived?
greater omentum: hangs from greater curvature of stomach and covers intestines (like an apron), formed from mesogastrium (mesentery)
lesser omentum: connects stomach and liver, formed from ventral mesentery
what finding would a fistula between esophagus and trachea cause on CXR?
air from trachea enters esophagus into stomach —> gastric distention on CXR
what 2 normal physiological processes occur in the midgut during embryological development?
- herniation (6th week): abdomen temporarily becomes too small, so intestines herniate through umbilical cord (reduction occurs by 12th week, failure = omphalocele)
- rotation: bowel rotates around superior mesenteric artery (SMA) such that cecum ends up in RLQ
omphalocele vs gastroschisis
omphalocele = intestines herniate through umbilical cord (normal process, but should reverse by 12th week of gestation), covered by peritoneum
gastroschisis = intestines extrude through abdominal wall, but NOT through umbilical cord and therefore NOT covered by peritoneum
how will volvulus (midgut malrotation) present?
volvulus = small bowel twists around superior mesenteric artery (SMA) —> vascular compromise —> ischemia/obstruction/necrosis
presents with vomiting, sepsis, abdominal distention, blood in stool
what is the cause of Meckel’s diverticulum?
persistent remnant of vitelline duct (connects bowel to yolk sac) —> causes outpouching (diverticulum) of small bowel (ileum)
true diverticulum because it contains ALL layers of bowel - mucosa, submucosa, AND MUSCULAR
[in other diverticulum, just sub/mucosa protrude through hole in muscular layer]
what is a Technetium scan used for?
used to dx Meckel’s diverticulum: persistent remnant of vitelline duct (connects bowel to yolk sac)
—> causes outpouching of small bowel + often ectopic gastric cells
Technetium scan: tracer taken up by gastric cells in diverticulum and emit signal
where is the most common and most rare location, respectively, for GI atresia or stenosis to occur?
most common = duodenum
most rare = colon
—> causes polyhydramnios and bilious vomiting
duodenal atresia is associated with which genetic disorder?
Down syndrome
appears as “double bubble” sign on imaging - distention of duodenum stump and stomach with tight pylorus in the middle (due to backup behind atresia)
what is the mechanism of duodenal atresia vs jejunal-ileal-colonic atresia?
duodenal atresia = failure of recanalization (“double bubble” sign of distended stomach + duodenum)
jejunal/ileal/colonic atresia = ischemic necrosis due to vascular disruption (“apple peel atresia” due to curling of bowel distal to blind end)
