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83 Cards in this Set

  • Front
  • Back
formation of primitive gut by what
transverse fold during 4th week
gut divided into what
foregut, midgut, hindgut
end of primitive hindgut
cloaca
separates cloaca from proctodeum
cloacal membrane
what is proctodeum
pit like depression on outside of embryo
cloaca becomes
rectum, anal canal, urethra
cloacal membrane does what
later breaks down – establishes connection to outside
attaches gut to posterior body wall?
dorsal mesentery
connects only foregut to anterior body wall
ventral mesentery
primitive gut lined with, and supported by – tissues?
lined with endoderm, supp. by splanchnic mesoderm
endoderm forms what in GI tract
tissue lining GI tract and its outgrowths (including lungs, airways)
endoderm also forms what structures that open to GI?
parenchyma=secretory cells=liver, GB, pancreas &lining
forms smooth muscle and conn. tissue of primitive gut?
mesoderm
connects primitive gut to yolk sac, obliterates when?
vitelline duct, gone by 5 – 6 week
where does the vitelline duct connect
midgut at terminal ileum (so remnants assoc. with term. ileum: MECKELS DIVERTICULUM!!
vitelline duct remnants in what % of pop, M vs. F?
more in males, in about 2% of people
Types of vitelline duct remnants:
fistula=Meckels D, cyst, or open fistula
why might diverticula and cysts develop on mesentery side of gut
between notochord and endoderm, because endoderm very close to gut, so small bits may stick together during dev.
foregut structures
respiratory tree (larynx – alveoli), esophagus, stomach, duodenum, liver, GB, pancreas
foregut development event summary
laryngotracheal diverticulum, gastric dilatation, foregut occulusion proximal and distal to the gastric dilatation (makes dilatation of gut), subsequent recanalization, elongation of esophagus, moving stomach to abdomen, rotation of stomach, differential growth of stomach, outgrowth of liver, GB, pancreas.
if laryngotracheal diverticulum doesn’t form correctly, what happens
fistula (polyhydramnios)
if foregut recanalization doesn’t occur properly, result?
stenosis or atresia in duodenum
if esophagus doesn’t elongate properly, what happens
stomach can’t move - abdomen, interferes w/ lung dev.
rotation of the stomach does what
dorsal border and mesentery to left side
dorsal mesentery forms what?
greater omentum, gastrosplenal, splenorenal ligaments
ventral mesentery forms what
liver coverings & ligaments, and lesser omentum
midgut forms
duodenum past comm. bile duct, jej/ileum,cecum, appendix, asc. colon, 2/3 trans. colon
which wall of the stomach grows faster?
dorsal wall
when does the stomach rotate 90 degrees clockwise around the longitudinal axis
during 7th week
what does the rotation produce?
lesser sac
where are the vagus nerves after the rotation?
left on anterior stomach, right on posterior
how does the stomach come to be in its adult orientation
next rotation is of stomach and duodenum about ventrodorsal axis, pulling end of stomach upwards
dorsal mesentery hanging from greater curve now called?
greater omentum
in umbilicus, which direction does the herniation of the midgut loop rotate?
counterclockwise
which half of the midgut elongates?
proximal half
elongation of the midgut creates?
coils of small intestine
how many degrees does the midgut rotate
270 in total
after midgut rotation complete, what happens?
loop moves into gut, rotates 180 degrees counterclockwise, then proximal end of intestine rotates another time 180 degrees
what does the final rotation accomplish?
duodenal-jejunal junction to adult location
where is cecum following return of the hernia to the abdomen?
initially subhepatic
how does cecum end up in right iliac fossa?
further gut elongation grows the ascending colon
if there is a malrotation – what occurs?
small intestine will be on one side, large intestine on other – diagnostic problems, confusing for examination & surgery
what % of population have malrotation
5%
failure of midgut to return to gut – name?
omphalocele – intestines within umbilical cord
repair if intestines in umbilicus?
surgery only if small omphalocele, otherwise staged surgery – stuffing all abdominal contents back in may inhibit breathing
tear of abdominal wall near umbilicus
gastroschisis – tissue becomes rigid and brittle – amniotic fluid bad for tissue
hindgut events
cloaca partitions, anal membrane breaks down
cloaca partitions into what
urogenital and anorectal canals
mechanism for partitioning
urorectal septum
contributes to the bladder and urethra?
urogenital sinus
rectoanal canal contribute to?
rectum and upper anus
distal anal canal develops from?
proctodeum
separates the cloaca from the proctodeum?
cloacal membrane
divides cloacal membrane into urogenital and anal membranes?
urorectal septum
in order for urogenital and anal systems to be open to exterior, what must happen?
urogenital and anal membranes must degenerate
if anal membrane doesn’t break down – condition?
congenital membranous atresia
if urorectal septum fuses with posterior cloaca rather than cloacal membrane – result?
complete anal atresia: VERY difficult to correct (no anal opening, no sphincters, etc.)
if incomplete fusion of urorectal septum and cloacal membrane – result?
because urorectal septum is bifid, incomplete fusion can mean fistulas connect urogenital and rectoanal organs
tissue type: liver and gallbladder
outgrowth of endoderm near distal foregut
pancreas develops as
dorsal pancreatic bud into dorsal mesentery, and ventral pancreatic bud into ventral mesentery
ventral mesentery bud gives rise to
half pancreas, gall bladder, liver
with stretching of mesentery during growth process, what does ventral mesentery become?
hepatic sinusoids and supportive connective tissue, liver capsule, lesser omentum, falciform, triangular and coronary ligaments of liver
how do pancreatic buds come together?
rotation of stomach and differential growth cause buds to join
what does ventral pancreatic bud become?
uncinate process
embryonic tissue becomes: diaphragm central tendon?
cranial part of septum transversum
rest of diaphragm
from dorsal mesentery assoc. w/ esophagus + projections of tissue: pleuroperitoneal folds from body wall
how does congenital diaphragmatic hernia occur?
pleuroperitoneal folds don’t complete separation of thoracic/abdominal cavity prior to return of midgut herniation back to abdominal cavity
when might a congenital diaphragmatic hernia occur?
10th week
obstruction consequences
distension proximally, reduced stool output
indicator of upper obstructions
projectile vomiting, at the time of feeding
lower obstructions
less forceful vomiting, delayed, with bile
if mother is too large for dates – expect
polyhydramnios – occlusion somewhere in GI tract
Obstruction causes
failure to recanalize, fetal vascular accident: if blood supply compromised, segment may fibrose, die
obstruction cause in stomach
congenital hypertrophic pyloric stenosis
pancreatic cause of obstruction
ring of pancreatic tissue that surrounds duodenum like a collar: annular pancreas
if bowel becomes twisted
congenital volvulus: can block both lumen and blood supply
problem with congenital volvulus
can become gangrenous – die
congenital volvulus occurs usually with
gut tubes that have, then lose mesentery asc/desc/duod
condition where bowel telescopes on itself
intussusception
condition where anus is stenosed by incorrect chamber division
imperforate anus
intestine of newborn contains
meconium: secretions, cells, detritis swallowed with amniotic fluid
when are intestinal contents passed
meconium passes in 1st 24 hrs
why might intestinal contents not pass? suspect what?
if too viscous (too much mucous) meconium won’t pass. common in kids with cystic fibrosus