GI Embryology

Question 1

which folding creates 3D trunk

Answer 1

transverse, GI tract from yolk sac

Question 2

what connects the GI tract/holds it in place in abdominal cavity

Answer 2

dorsal mesentary

ventral goes away except in upper abdomen

Question 3

3 divisions of Gut and their main components

Answer 3

1. foregut- pharynx, esophagus, stomach, duodenum (also pancreas and liver)
2. midgut- duodenum, jejunum, ileum, cecum, ascending colon, beginning of transverse colon
3. hindgut- rest of transvers, descending colon, sigmoid, rectum, anal canal

Question 4

vascular supply to each gut area

Answer 4

foregut- celiac trunk (except pharynx)
midgut- SMA
hindgut- IMA

all branches off aorta

Question 5

describe development of midgut loop

Answer 5

herniates into umbilical cord as a loop with two limbs

cranial limb gets long and folds, becomes small intestine

caudal limb doesnt get long, becomes proximal large intestine

loop retuns to ab cavity in week 10, cranial first then caudal

Question 6

how does the lumen of the GI tract develop

Answer 6

originally patent, then filled, then recanalized

Question 7

duodenal atresia epi/patho/clinical

Answer 7

w/ downs

failure of recanalization

bilious vomiting, double bubble on Xray where duodenum should begin

Question 8

congenital pyloric stenosis epi/patho/clin

Answer 8

common esp males

pyloric wall hypertrophy

palpable mass, projectile non bilious vomiting (upstream of bile deposition)

Question 9

umbilical hernia patho/clin

Answer 9

midgut returns to abdomen in week 10 but re-herniate

midline protrusion w/ abdominal contents, covered by skin

Question 10

omphacele pahto/clin

Answer 10

persistence of herniated intestines

midline protrusion at navel, covered by peritoneum like sac rather than skin

Question 11

gastroschisis patho/clin

Answer 11

ab wall fails to close after intestines return to abdomen

protrusion near but not at midline, not covered by skin or peritoneum

Question 12

Meckel’s diverticulum, path and histo

Answer 12

rule of 2s:

• 2% of pop
• 2ft from ileocecal junction and 2 in long
• appears in first 2 years

patho: remnant of vitelline duct
histo: gastric epithelium and/or pancreatic tissue lining

Question 13

hirschprung’s disease etiology, patho. gross path, clin

Answer 13

absence of innervation in wall of distal GI (meissners and auerbachs ganglia)

lack of normal migration of neural crest cells to distal colon/rectum

aganglionic area is constricted, proximal area is dilated (can cause gongenital megacolon

constipation, failure to pas meconium

Question 14

site of liver development

Answer 14

ventral mesentery- falciform ligament is anterior, hepatogastric is posterior

enlarges and rotates into right ab area

Question 15

2 precursors to pancreas

Answer 15

ventral bud (head of pancreas and main duct) and dorsal bud (head, body, and tail) of the mesenteries

eventually ventral rotates and fuses w/ dorsal on left side of GI tract

Question 16

final location for pancreas

Answer 16

pushed left and posterior by liver and other organs, eventually fuses in place retroperitoneal

Question 17

other elements of ventral bud invagination

Answer 17

bile duct and liver and gallbladder