Embryology of GI Tract Flashcards
what weeks are the embryonic period
- weeks 3-8
what happens in the fetal period
- growth and maturation
what is the result of injury during the embryonic period
- major congenital anomalies
when are the three germ layers formed?
- week 3
we begin week 4 as what kind of embryo
- flat embryo
what does longitudinal folding do
- moves the heart in the new thorax
what does transverse folding do
- creates a 3D trunk
transverse folding creates the GI tract from what
- yolk sac
GI tract lies where
- peritoneal cavity
GI tract suspended by
- mensentaries
what happens with the dorsal mesentary
- remains
- suspends GI tract
what does the dorsal mesentery contain
- vasculature
what happens with the ventral mesentary
- disappears except in upper abdomen (liver)
what is a mesentery
- connective tissue that suspends GI tract in peritoneal cavity and attaches to abdominal wall
what does the mesentery carry
- blood and nerve supply to suspended organs
what germ layer creates the liver, pancreas, and epithelium of the GI tract
- endoderm
what germ layer creates the connective tissue and muscle of viscera
- lateral endoderm
what does the foregut become
- pharynx
- esophagus
- stomach
- part of duodenum
- pancreas
- liver
what does the midgut become
- duodenum
- jejunum
- ileum
- cecum
- ascending colon
- 2/3 of transverse colon
what does the hindgut become
- rest of transverse colon
- descending colon
- sigmoid colon
- rectum
- cranial anal canal
what vascularizes the foregut
except
- celiac trunk
- NOT PHARYNX
what vascularizes the midgut
- superior mesenteric artery
what vascularizes the hindgut
- inferior mesenteric artery
the entire GI tract begins as a
- tube
how does the midgut form
- extends out (herniates) as a loop into the umbilical cord
what happens to the cranial limb of the midgut
- grows long and forms folds
what does the cranial limb of the midgut become
- small intestines
what happens to the caudal limb of the midgut
- doesn’t grow long
what does the caudal limb of the midgut become
- proximal large intestines
when do the cranial and caudal limb of the midgut retune to the abdominal cavity
which goes first
then what happens
- week 10
- cranial before caudal
- they rotate into final positions
development of the tract - specifically the tube
- originally patent (open lumen)
- fills in (closed lumen)
- recanalizes (open lumen)
in patients with which condition do we also see duodenal atresia
- down syndrome
pathogenesis of duodenal atresia
- failure of recanalization
clinical symptoms of duodenal atresia
- bilious vomiting
x ray of duodenal atresia
- double bubble
what is atresia
- absence of or narrowing of opening or passage in the body
congenital pyloric stenosis - common or uncommon
- common in males
pathogenesis of congenital pyloric stenosis
- pyloric wall hypertrophy
clinical symptoms of congenital pyloric stenosis
- palpable mass
- projective non-bilious vomiting
pathogenesis of umbilical hernia
- after intestines return to abdomen in week 10, they reherniate through imperfectly closed umbilicus
what does a umbilical hernia look like
- midline protrusion containing small quality of abdominal contents
- covered by skin
omphalocele pathogenesis
- persistence of herniated intestines that do not return to abdomen in week 10
what does omphalocele look like
- midline protrusion at navel containing intestines
- covered by peritoneum-like transparent sac
gastroschisis pathogenesis
- abdominal walls fails to close after intestines return to abdomen
what does gastroschisis look like
- protrusion of GI tract near but not in midline
- not covered by skin or peritoneum
meckel’s diverticulum epidemiology
- most common congenital anomaly of GI tract
pathogenesis of meckel’s diverticulum
- remnant of vitelline duct
what is the vitelline duct
- temporary structure that joins yolk sac to developing midgut
anatomy of meckel’s diverticulum
- distal small intestine
- 2 ft from ileocecal junction
- 2 inches long
histopathogloy of meckel’s diverticulum
- may have gastric epithelium or pancreatic tissue lining
clinical symptoms of meckel’s diverticulum
- bleeding, intussusception, volvulus, obstruction in first 2 years of life
Hirschsprung’s disease etiology
- absence of innervation in wall of distal GI
pathogenesis of Hirschsprung’s disease
- normal migration of neural crest cells that would become ANS neurons does not occur into distal colon or rectum
what do we see in the aganglionic area in Hirschsprung’s disease
- constricted
what do we see in the proximal area in Hirschsprung’s disease
- dilated
- can become congenital megacolon
clinical symptoms of Hirschsprung’s disease
- failure to pass meconium
- constipation
liver develops from
- ventral mesentary
ventral mesentery composed of
- falciform ligament
- hepatogastric ligament
where is the falciform ligament relative to the liver
- anterior to liver
where is the hepatogastric ligament relative to the liver
- posterior to liver
what happens to the liver as it enlarges during development
causes
- rotates into right abdominal area
- rotation of stomach and spleen into final orientations and locations
what does the pancreas arise from
- ventral and dorsal pancreatic bud of mesentary
ventral bud of pancreas arises from same invagination as
- liver
- bile duct/gallbladder
which bud of the pancreas fuses with which
where
- ventral rotates and fuses with dorsal
- on left side of GI tract
what does the ventral bud of the pancreas become
- head of pancreas
- main pancreatic duct
- carries bile with it
what does the dorsal bud of the pancreas become
- head, body and tail of pancreas
as the liver and other organs develop and grow in the mesentery, what happens to the pancreas
- pushed until it lies along left posterior abdominal wall
- fuses in place and becomes retroperitoneal
