Embryology of the GI tract Flashcards
the stomodeum and proctodeum are derived from what germ layer?
ectoderm
embryologically where does the midgut begin?
duodenum distal to bile duct
embryologically where does the hind gut begin?
distal transverse colon
the liver, pancreas, and gall bladder are what part of the gut?
foregut
the esophagus and larynx/trachea are derived from what part of the gut?
foregut
during what week does the primitive gut develop?
4th week
the tracheoesophageal septum divides the foregut into what components? during what week does this occur?
laryngotracheal tube and esophagus
week 4
what is responsible for partially or completing obliterating the esophageal lumen?
epithelium
what are the three mechanisms that can cause esophogeal stenosis?
sequestration of respiratory tissue elements
fibromuscular hypertrophy due to myenteric nerve plexus damage
a mucosal diaphragm is present
what are the three malformations of the esophagus
esophageal atresia
tracheoesophageal fistula
esophageal stenosis
what is the lusorian artery?
anomalous right subclavian artery, coming off aortic arch to the left of the left subclavian and traveling retroesophageally
what marks the site of the future stomach?
dilitation of caudal foregut
is the rate of dilitation of the stomach greater dorsally or ventrally?
dorsal dilitation is more rapid
how does the stomach rotate
clockwise rotation 90 degrees
what is the mnemonic for the orientation of the vagus nerves in relation to the stomach?
LARP
left anterior right posterior
what are the features of infantile pyloric stenosis?
thickened pylorus
pyloric sphincter hypertrophied
food passage restricted
projectile vomiting
how is infantile pyloric stenosis treated?
myotomy
what is the sign of infantile pyloric stenosis?
projective vomiting
what artery supplies the foregut portion of the duodenum?
celiac trunk
what artery supplies the midgut portion of the duodenum?
SMA
will there be bile present in the projectile vomit of infantile pyloric stenosis?
no
will there be bile present in the vomit of duodenal stenosis?
yes, usually
will there be bile present in the vomit of duodenal atresia?
almost always
what are the causes of duodenal obstruction?
incomplete recanalization (stenosis), usually annular pancreas (stenosis) recanalization does not occur - atresia mutations in sonic hedgehog signaling
the double bubble sign is consistent with what diagnosis?
duodenal stenosis
what is the most common cause of jejunal and ileal atresia and stenosis?
vascular accident
what are the three stages of midgut rotation?
herniation into umbilical cord
reduction of herniation into abdominal cavity
fixation
which midgut limb forms the intestinal loops?
cranial
why does the vermiform appendix form?
the apex of the cecal diverticulum does not grow as rapidly as the rest of it
what is omphalocele? what is the cause?
intestines do NOT return to abdominal cavity during 10th week - covered by amnion
incomplete closure of lateral folds
what is umbilical hernia? what is the cause?
intestines do NOT return to abdominal cavity but then herniate prenatally or postnatally
what is nonrotation of the midgut? what is the result?
only 90 degrees of rotation occur
left sided colon
what is reversed rotation? what is the result?
midgut loop rotates 270 degrees in a CLOCKWISE direction
duodenum is anterior to SMA, transverse colon is posterior to SMA
what is the result of mixed rotation? how is it observed on imaging?
cecum inferior to to pylorus
peritoneal bands descend over duodenum
peritoneal bands and volvulus usually cause a duodenal obstruction
corkscrew and whirlpool signs
what does meckel’s diverticulum represent embryologically?
remnant of proximal part of yolk stalk
what is the cloaca?
terminal portion of hindgut, lined by endoderm that is in contact with surface ectoderm at cloacal membrane
what makes up the cloacal membrane?
ectoderm of proctodeum
endoderm of cloaca
the intersphincteric junction is demarcated by what boundary?
white line of Hilton
what is the epithelium above and below the white line of Hilton?
above - stratified squamous nonkeratinized
below - stratified squamous keratinized
what is the lymphatic drainage of the cranial 2/3 of the anal canal? caudal 1/3?
cranial 2/3 - inferior mesenteric
caudal 1/3 - superior inguinal
what is the most common cause of familial intrahepatic cholestasis?
alagille syndrome (paucity of interlobular ducts)
what characterizes familial intrahepatic cholestasis?
decreased number of bile ducts in the portal spaces
what causes annular pancreas? what can it cause?
bifid ventral bud seems to be the cause
may cause obstruction of dorsal bud
what causes pancreas divisum? what can it lead to?
ventral and dorsal pancreatic ducts do not fuse
chronic pancreatitis
