Embryo-Digestive System

  1. Germ layers
    • Endoderm: epithlelium (except mouth and anal canal)
    • Mesoderm: splanchnic mesoderm (smooth muscle, connective tissue, blood vessels)
    • Neural Crest: autonomic ganglion (vagus)
    • Ectoderm: mouth (1st arch portion) and anal canal
  2. Divisions of hte Digestive System
    • Foregut
    • Midgut
    • Hindgut
  3. Foregut
    • Pharynx and derivatives, respiratory system (6th arch)
    • Esophagus, stomach, liver and pancreas, biliary apparatus, proximal duodenum (superior to yolk sac)
  4. Midgut
    • Small intestine
    • cecum and vermiform appendix
    • ascending colon
    • right half of transverse colon
  5. Hindgut
    • left half of transverse colon
    • descending colon
    • signmoid colon
    • rectum
    • superior anal canal
    • epithelium of urinary bladder/urethra
  6. vessels of the digestive system
    • foregut-celiac trunk
    • esophagueus to duodenum
    • midgut-SMA
    • Hindgut-IMA, left transverse to rectum
    • SMA-axis of rotation for midgut
    • viteloduct (endoderm)=same plan as SMA-another axis
  7. Esophagus
    • endoderm
    • 6th arch
    • primitive pharynx
    • traneoesophageal septum-divides
    • abnormalities-problems with tracheoesophagea septum -frothy saliva (bubbly) after being freed
    • -esophageal atresia
    • -fistula
  8. stomach
    • rotation-90 degree rotation on longitudinal axis
    • -ventral border to right
    • -dorsal border to left
    • -left side becomes ventral
    • -right side becomes dorsal
    • "left hand turn 90 degrees"
    • growth-posterior side=rapid
  9. liver and biliary system
    • endoderm
    • parenchyma-business portion-produce liver enzyme
    • -not in contact with external environment, no foreign food comes in contact here
    • hepatic duct and bile duct
    • all come from a single diverticulum
  10. pancreas
    • endoderm
    • dorsal primordia-body
    • ventral primordia-near liver, head
    • main duct-ventral duct
    • opening in duodenum where main pancreatic duct and bile duct meet-duodenal papilla
    • -rotation-as duodenum rotates to right, ventral pancreatic bud is carried dorsally
    • --180 degree rotation of ventral primordia to fuse with dorsal primordia
    • -abnormalities-anular pancreas (obstruction of duodenum because of rotation to the left)
    • "craddle in duodenum and tickles the spleen"
  11. spleen
    • splanchnic mesoderm
    • lymphnoid organ for blood sequestering platelets
    • foregut
  12. midgut formation
    • rotation-out at 6 weeks, back at 10 weeks
    • -rotates 90 degrees when it leaves, 90 degrees out in coelom, 90 degrees when it comes back=270 total
    • leaves for liver-blood formation; yolk sac=3-8 wk; liver=6-30 wk; spleen=9-28 wk (helps liver), bone marrow=28 wk to adulthood
    • lumen formation-definitive gut lumen
    • -endoderm=proliferates into solid tube-recanalization (apotosis occurs (cell death))-hollow gut
  13. abnormalities in midgut
    • nonrotation-obstructions can occur; SI-right side; LI-left side
    • reversed rotation-transverse colon adherent to body wall (retroperitoneal)
    • duplication-food can get trapped, inflammation, infection, rupture tube
    • stenosus-narrowing of GI tube, food can get trapped, severe pain, vomitin
  14. hindgut formation
    • urorectal septum
    • -cloaca (endoderm and ectoderm)-common anatomicla area where products from digestion, urinary and reproductive tracts can exit the body
    • -clocal membrane (endoderm and ectoderm)
    • -urorectal septum (mesoderm) grows toward the cloacal membrane and divides it
    • --urogenital membrane (endoderm and ectodorm)
    • --anal membrane (endoderm and ectoderm)
    • ---no blood supply-degenerates openings (anus, vagina, uretra)
    • anal canal
    • -superior from hindgut (endoderm); superior rectal a. and v. (autonomic involuntary control-N.C.)
    • -inferior from proctodeum (ectoderm)-inferior rectal a. and v. from internal pudendal a.
    • -different blood an dnerve supply
  15. anorectal malformations
    • septum migrate and separate the cloaca (mesoderm)
    • endoderm and ectoderm layers must meet at the right place
    • anal stenosis
    • covered anus-anal agenesis
    • recto-urethral fistula-anus goes into urethra
  16. Meckel's Diverticulum
    • Abnormality of the vitelline duct (endoderm)-normally regresses
    • Projection from ilium to abdominal wall
    • can lead to intestinal obstruction, gastrointestinal bleeding, bowel spesis(rupture)
  17. Formation of the pleural-peritoneal membrane
    • pericardial cavity separated from pleural canals by pleuropericardial folds (mesoderm)
    • lungs develop in area between pleuropericardial membrane and the pleuroperitoneal membrane
    • septum transversum meets with the pleuroperitoneal membranes(mesoderm)
    • below septum transversum and pleuroperitoneal membrane is the peritoneal cavity
  18. closure of pericardioperitoneal canal
    • septum transversum (mesoderm)-doesn't migrate to post. wall
    • pleuroperitoneal membrane (mesoderm)-from post. wall
    • -somatic layer
    • -grow toward septum transversum and fuse
    • tissue from body wall pulled into the diaphragm-somites (para-axial mesoderm)
  19. formation of diaphragm
    • septum tranversum (central tendon)
    • pleuroperitoneal membranes (mesoderm)
    • -dorsal mesentery fo esophagus (crura)-mesoderm
    • -body wall (peripheral muscles)-somites
  20. hernias
    • 50%-esophageal hernias
    • 36%-lef. side through posterolateral part
    • -failure of pleuroperitoneal membrane and septum transversum
  21. peritoneal cavity
    • mesentery: double layer of serous membrane (splanchnic)-provide way of blood vessels, n., and lymphatics to reach organs
    • dorsal mesentery-entire GI tract has at some point
    • ventral mesentery-only see in foregut
    • visceral layer-organ
    • parietal layer-on body wall; together with visceral layer make peritoneum in adult
  22. foregut and heart mesenteries
    • meso-esophagus-b/t neural tube and esophagus
    • dorsal mesocardium-b/t esophagus and heart-degenerate-transverse sinus
    • ventral mesocardium-b/t heart and ant. body wall-degenerates
  23. midgut and hindgut mesenteries
    • mesoduodenum
    • mesentery proper-around S.I.=duodenum and jejunum
    • mesocolon-transverse colon
    • mesorectum-sigmoid colon
  24. peritoneal cavity
    • dorsal mesogastrium
    • ventral mesogastrium
    • ventral mesentery
    • greater omentum
  25. dorsal mesogastrium
    • mesoderm
    • stretches with rotation of stomach
    • -splenorectal (leinorenal ligament)-b/t spleen and kidney
    • -gastroleinal ligament-b/t somach and spleen
    • -greater omentum-3 lig (gastrophrenic, gastrosplenal, gastrocolic)
  26. ventral mesogastrim
    • mesoderm
    • b/t stomach and liver
    • lesser omentum
  27. ventral mesentery
    • falciform ligament
    • mesoderm
  28. greater omentum
    • due to all 3 rotations
    • -omentum bursa
    • -fusion of double layers (mesoderm)
  29. fusions of mesenteries with body walls
    • mesogastrium dorsal to spleen-pancreas fused to body wall
    • mesoduodenum-2,3, 4th retro (fused to body wall)
    • ascending mesocolon and descending mesocolon-mesoderm
    • fixation of gut
  30. intraperitoneal
    • mesoderm
    • completely suspended in mesentery-freely move
    • -stomach
    • -first part of duodenum
    • -jejunum, ileum
    • -transverse colon
    • -sigmoid colon-flexible post.
  31. retroperitoneal
    • mesoderm
    • fixed to body wall
    • -pancreas (except tail)
    • -duodenum (2-4)
    • -ascending colon
    • -descending colon
    • -esophagus
    • -rectum
  32. omphalocele an dcongenital umbilical hernia
    • endoderm
    • failure of intestine to return to abdomen between 6 and 10
  33. gastroschisis
    • due to folding-mesoderm
    • herniation of abdominal contents during week 4 due to muscular defect in abdominal wall
  34. congenital diaphragmatic hernia
    • peritoneal membrane failure
    • herniation into thoracic cavity due to failure of the components of the diaphragm to fuse properly (mesoderm)
  35. congenital inguinal hernia
    • mesoderm
    • trapping or constriction of intestines
  36. congenital megacolon
    N.C.-fail to migrate down to that part of intestin-causes obstruction, huge colon in front
  37. congenital hypertrophic pyloric stenosis
    • N.C.
    • enteric N.C. plexus
Card Set
Embryo-Digestive System