embryo Flashcards
What parts of the GI are from endoderm?
mucosal epithelium and GI glands
What parts of the GI are from mesoderm?
muscular wall, smooth muscle, connective tissue, vasculature
What parts of the GI are from ectoderm?
neural crest - enteric ganglia, nerves, glia
ectoderm- mouth and anal canal
What are the derivatives of the foregut?
pharynx to proximal duodenum, liver, pancreas, gallbladder
What are the derivatives of the midgut?
latter duodenum to right half of transverse colon, including appendix
What are the derivatives of the hindgut?
left half of transverse colon to superior anal canal, epithelium of bladder and urethra
What blood supplies the foregut?
celiac trunk
What blood supplies the midgut?
superior mesenteric artery
What blood supplies the hindgut?
inferior mesenteric artery
Describe the rotation of the stomach in 4 events:
- ventral border rotates to the right
- dorsal border rotates to the left
- left side becomes ventral
- right side becomes dorsal
then growth and rotation along AP axis
What are the prenatal and postnatal signs of a tracheoesophageal fistula?
prenatally: polyhydramnios
postnatally: coughing, gagging, cyanosis, vomiting, oral secretions, resp. distress
What happens in hypertrophic pyloric stenosis? What are the presentations?
circular and longitudinal muscles hypertrophy
immediate post feeding vomiting, fewer and smaller stools, failure to gain weight
What does the hepatic diverticulum give rise to?
liver, gallbladder and ventral pancreatic bud
the stalk becomes the hepatic duct and bile duct
How does the pancreas form?
ventral pancreatic bud migrates to dorsal side.
what does the dorsal pancreatic bud give rise to?
body and tail of pancreas
what does the ventral pancreatic bud give rise to?
head and uncinate process
what happens with an annular pancreas? whats the embryological causing?
obstruction of duodenum; symptoms similar to pyloric stenosis
head of pancreas is bifed; malrotation causes the site of duodenal obstruction
what do we need to know about the spleen?
the spleen is foregut but is made from mesoderm
forms from week 5
is a hematopoetic organ and helps with hematopoesis in weeks 9-28
how is midgut formed?
it herniates out into umbilicus at week 6, with the SMA becoming the axis
it then rotates 90 counterclockwise and a buldge appears for the cecum and the proximal part becomes convoluted
the proximal part returns into the abdomen, passes under distal portion towards the left and then the distal part returns
what is an omphalocele? Which week?
failure of the bowel to return to body cavity (its covered by peritoneum); week 10
What is gastroschisis? Which week does it happen in?
failure of body wall to close. no peritoneum. Week 4.
What is the embryological mechanism of hirschsprung disease?
problem with neural crest cells; absence of ganglion
What happens if you have midgut nonrotation?
SI on right side and LI on left side
usually no symptoms but could have higher likelihood of obstruction
What happens with reverse rotation of midgut?
transverse colon becomes posterior to duodenum and can cause obstruction of TC;
caused by wrong 180 degree rotation
How do we form the definitive gut lumen? What can go wrong?
epithelial cells fill lumen, then apoptosis and recanalization.
duplication or stenosis
What is the rule of 2s for meckels diverticulum?
2% of population 2 feet from ileocecal junction 2 inches long 2 types of ectopic tissue (gastric and pancreatic usually) 2 years age of presentation 2x likely to affect males
What is meckel’s diverticulum caused by?
incomplete obliteration of vitelline duct, pulls on ileum and causes outpouching
What is an omphalomesenteric fistula?
abnormal opening in the vitelline duct, causing poop to leave umbilicus
What other two things could arise from Meckel’s diverticulum?
omphalomesenteric cyst and omphalomesenteric ligament
What does the urorectal septum separate the cloaca into?
urogenital membrane (forms bladder and urethra) and anal membrane (forms anus)
both are ectoderm and endoderm
What causes a congenital diaphragmatic hernia? What are the characteristics?
defective formation and/or fusion of the pleuroperitoneal membranes - large opening in posterolateral diaphragm
herniation of abdominal contents, hypoplastic lungs, polyhydramnis
Where does the mesentary come from?
splanchnic layer
Where does the parietal peritoneum come from?
somatic layer of lateral plate mesoderm
What is the purpose of the mesentaries?
to allow vessels to get to the organs; most of them degenerate
What does the dorsal mesocardium give rise to?
transverse pericardial sinus
What does the dorsal mesogastrium give rise to?
greater omentum
What does the ventral mesogastrium give rise to?
lesser omentum
What does the ventral mesentery give rise to?
falciform ligament
What does the mesoduodenum give rise to?
mesentery around duodenum
What does the mesentery proper give rise to?
mesentery containing jejunum and ileum
What does the mesocolon give rise to?
mesentery around transverse colon and sigmoid colon
What does the mesorectum give rise to?
mesentary around the rectum
What ligaments does the dorsal mesogastrium give rise to?
splenorenal ligament and gastrolienal ligament
Which structures are intraperitoneal?
stomach, tail of pancreas, first part of duodenum, jejunum, ileum, transverse colon, sigmoid colon
Which structures are retroperitoneal?
pancreas (except tail), duodenum (2nd-4th parts), ascending colon,
descending colon
