GI embryo flashcards
(71 cards)
what happens on day 16?
gastrulation (epiblast forms the 3 layers:epi, meso and endoderm)
what layers contribute to the gut tube?/GI system?
All 3: endoderm, mesoderm, ectoderm
What does the endoderm form?
the epithelial lining from pharynx to the upper 2/3s pf the anal canal, and the epithelium of all the glands/organs that are extensions of the gut tube
What are the GI accessory organs/glands that form from the gut tube?
submandibular and sublingual glands, liver, pancreas and gall bladder
What does the mesoderm form in the GI system?
connective tissue, mesentary and smooth muscle
What does the ectoderm form in the GI system?
the nerves; and the epithelium in mouth and lower 1/3 of anal canal
what is Hirshsprung disease?
failure of the ectoderm’s neural crest cells to migrate to the caudal 1/3 of the colon–> resulting in megalocolon
how does the endoderm end up lining the inside of the gut tube?
folding of the embryo
what stays outside when the folding occurs?
the yolk sac and the allantois
remind me, what is the allantois and the yolk sac?
the allantois is a diverticulum of the gut tube near the cloaca, and becomes (mostly) the urinary bladder in the adult, the other part eventually becomes part of the umbilical cord by joining the vitilline duct (yolk sac stalk) and blood vessels but is initially on its own (partially in and out of the embryo); the allantois does nothing in humans and will degrad to wharton’s jelly in the umbilical cord with the vitilline duct; the yolk sac is thought to provide nutrients to the embro initially and is a place where gonadal stem cells reside for a while before going to their respective places
as an embryo, can fluids pass through the gut tube?
not initially, the tubes are blind-ended at the mouth and anus until the 5th and 7th weeks, respectively
what are the different portions of the gut tube?
foregut, midgut, hindgut
what part is the foregut in the embryo? The adult?
from the buccopharyngeal membrane through the pharynx to the liver bud; in the adult it goes from the pharynx to the 2ndpart of the doudenum (including the pancreas, liver and gall bladder
how is blood/nutrients mainly supplied to the foregut?
by the celiac artery
what part is the midgut of the embryo and the adult?
the lower 1/2 of the duodenum to 2/3 of the transverse colon; parts 3 nd 4 of the duodenum, small intestine, cecum, appendix, ascending and the rt. 2/3s of the transverse colon
what vessel supplies the midgut?
the superior mesenteric artery
what part of the gut tube in the embryo and adult form the hindgut?
lower 1/3 of the transverse colon to the cloacal membrane; the left 1/3 of the transverse colon to the upper 2/3s of the anal canal
what vessel supplies the hindgut?
the inferior mesenteric artery
how does the stomach develop and end up in it’s position with an anterior and posterior vagal trunk sandwiching it?
the dorsal aspect grows faster than the ventral surface, it rotates 90 deg around the vertical axis so that the rt vagus nerve becomes posterior and the left vagus nerve becomes anterior, the stomach also shifts to the left and rotates 45 deg in a coronal plane
What is formed due to the pulling of the dorsal mesentery as the stomach positions itself?
the lesser sac
what is the greater omentum formed from and how did it get there?
stretched out from the dorsal mesentery as the stomach rotated– it hangs off the greater curvature of the stomach and posterior wall
what is the general shape of the duodenum and how did it get that way?
it is a “c” shape– it is pulled superiorly and to the rt as the stomach rotates and the pancreas grows
what is the blood supply to the duodenum?
anastamoses from both the celiac and the superior mesenteric arteries
during the 2nd month, the lumen of the duodenum is obliterated, but then recanalized by apoptosis- if not recanalized a person will have what problem?
duodenal atresia or stenosis if partially blocked, or perhaps biliary atresia if the main pancreatic duct is blocked
