Embryology of the GI tract

Question 1

the stomodeum and proctodeum are derived from what germ layer?

Answer 1

ectoderm

Question 2

embryologically where does the midgut begin?

Answer 2

duodenum distal to bile duct

Question 3

embryologically where does the hind gut begin?

Answer 3

distal transverse colon

Question 4

the liver, pancreas, and gall bladder are what part of the gut?

Answer 4

foregut

Question 5

the esophagus and larynx/trachea are derived from what part of the gut?

Answer 5

foregut

Question 6

during what week does the primitive gut develop?

Answer 6

4th week

Question 7

the tracheoesophageal septum divides the foregut into what components? during what week does this occur?

Answer 7

laryngotracheal tube and esophagus

week 4

Question 8

what is responsible for partially or completing obliterating the esophageal lumen?

Answer 8

epithelium

Question 9

what are the three mechanisms that can cause esophogeal stenosis?

Answer 9

sequestration of respiratory tissue elements
fibromuscular hypertrophy due to myenteric nerve plexus damage
a mucosal diaphragm is present

Question 10

what are the three malformations of the esophagus

Answer 10

esophageal atresia
tracheoesophageal fistula
esophageal stenosis

Question 11

what is the lusorian artery?

Answer 11

anomalous right subclavian artery, coming off aortic arch to the left of the left subclavian and traveling retroesophageally

Question 12

what marks the site of the future stomach?

Answer 12

dilitation of caudal foregut

Question 13

is the rate of dilitation of the stomach greater dorsally or ventrally?

Answer 13

dorsal dilitation is more rapid

Question 14

how does the stomach rotate

Answer 14

clockwise rotation 90 degrees

Question 15

what is the mnemonic for the orientation of the vagus nerves in relation to the stomach?

Answer 15

LARP

left anterior right posterior

Question 16

what are the features of infantile pyloric stenosis?

Answer 16

thickened pylorus
pyloric sphincter hypertrophied
food passage restricted
projectile vomiting

Question 17

how is infantile pyloric stenosis treated?

Answer 17

myotomy

Question 18

what is the sign of infantile pyloric stenosis?

Answer 18

projective vomiting

Question 19

what artery supplies the foregut portion of the duodenum?

Answer 19

celiac trunk

Question 20

what artery supplies the midgut portion of the duodenum?

Answer 20

SMA

Question 21

will there be bile present in the projectile vomit of infantile pyloric stenosis?

Answer 21

no

Question 22

will there be bile present in the vomit of duodenal stenosis?

Answer 22

yes, usually

Question 23

will there be bile present in the vomit of duodenal atresia?

Answer 23

almost always

Question 24

what are the causes of duodenal obstruction?

Answer 24

incomplete recanalization (stenosis), usually 
annular pancreas (stenosis) 
recanalization does not occur - atresia 
mutations in sonic hedgehog signaling

Question 25

the double bubble sign is consistent with what diagnosis?

Answer 25

duodenal stenosis

Question 26

what is the most common cause of jejunal and ileal atresia and stenosis?

Answer 26

vascular accident

Question 27

what are the three stages of midgut rotation?

Answer 27

herniation into umbilical cord
reduction of herniation into abdominal cavity
fixation

Question 28

which midgut limb forms the intestinal loops?

Answer 28

cranial

Question 29

why does the vermiform appendix form?

Answer 29

the apex of the cecal diverticulum does not grow as rapidly as the rest of it

Question 30

what is omphalocele? what is the cause?

Answer 30

intestines do NOT return to abdominal cavity during 10th week - covered by amnion

incomplete closure of lateral folds

Question 31

what is umbilical hernia? what is the cause?

Answer 31

intestines do NOT return to abdominal cavity but then herniate prenatally or postnatally

Question 32

what is nonrotation of the midgut? what is the result?

Answer 32

only 90 degrees of rotation occur

left sided colon

Question 33

what is reversed rotation? what is the result?

Answer 33

midgut loop rotates 270 degrees in a CLOCKWISE direction

duodenum is anterior to SMA, transverse colon is posterior to SMA

Question 34

what is the result of mixed rotation? how is it observed on imaging?

Answer 34

cecum inferior to to pylorus
peritoneal bands descend over duodenum
peritoneal bands and volvulus usually cause a duodenal obstruction

corkscrew and whirlpool signs

Question 35

what does meckel’s diverticulum represent embryologically?

Answer 35

remnant of proximal part of yolk stalk

Question 36

what is the cloaca?

Answer 36

terminal portion of hindgut, lined by endoderm that is in contact with surface ectoderm at cloacal membrane

Question 37

what makes up the cloacal membrane?

Answer 37

ectoderm of proctodeum

endoderm of cloaca

Question 38

the intersphincteric junction is demarcated by what boundary?

Answer 38

white line of Hilton

Question 39

what is the epithelium above and below the white line of Hilton?

Answer 39

above - stratified squamous nonkeratinized

below - stratified squamous keratinized

Question 40

what is the lymphatic drainage of the cranial 2/3 of the anal canal? caudal 1/3?

Answer 40

cranial 2/3 - inferior mesenteric

caudal 1/3 - superior inguinal

Question 41

what is the most common cause of familial intrahepatic cholestasis?

Answer 41

alagille syndrome (paucity of interlobular ducts)

Question 42

what characterizes familial intrahepatic cholestasis?

Answer 42

decreased number of bile ducts in the portal spaces

Question 43

what causes annular pancreas? what can it cause?

Answer 43

bifid ventral bud seems to be the cause

may cause obstruction of dorsal bud

Question 44

what causes pancreas divisum? what can it lead to?

Answer 44

ventral and dorsal pancreatic ducts do not fuse

chronic pancreatitis