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UNSW Embryology

Gastrointestinal Tract Overview

© Dr Mark Hill (2011)

Acknowledgements

Introduction

This section of notes gives an overview of how different early layers give rise to specific components of the gastrointestinal tract. Read specific parts of the table from left to right to see how a developmental sequence occurs.

Components of GIT Formation

surface ectoderm | primitive endoderm

surface ectoderm

  • buccopharyngeal membrane
    • membrane breaks down, creating opening.
  • anal pit
    • anal canal (caudal part)
    • anal membrane perforates

primitive endoderm

  • foregut diverticulum (pocket)
    • pharyngeal region of foregut
      • laryngo-tracheal groove (see respiratory tract)
      • oesophageal region of foregut
        • oesophagus
          • stomach
            • glandular/proventricular/pyloric stenosis
              • fundus/pyloric antrum
                • pyloric sphincter
            • dorsal mesogastrium
              • lieno-renal ligament
                • splenic primordium
                  • spleen
                • gastro-splenic ligament
            • duodenum (rostral half)
  • foregut-midgut junction
    • septum transversum
      • hepatic diverticulum
        • cystic primordium
          • gall bladder
            • common bile duct
              • hepatic ducts
                • liver/gall bladder
      • hepatic primordium
        • hepatic parenchyma
          • hepatic sinusoids
            • lobes of liver
              • liver/gall bladder
    • pancreatic primordium
      • left & right lobes
        • body/tail uncinate process
          • pancreas
  • midgut region
    • duodenum (candal half)
      • jejunum
    • midgut
      • physiological umbilical hernia
      • midgut loop returns to peritoneal cavity
  • hindgut diverticulum (pocket)
    • hindgut
      • distal hindgut (+urorectal septum)
        • rectum (+perineal body)
          • anal canal (rostral part) (+anal sphincter (external & internal))
            • ano-rectal junction
    • cloaca (surface ectoderm?)
      • cloacal membrane
        • urogenital sinus
          • bladder (+perineal body)
            • bladder

Modified from The Anatomical Basis of Mouse Development Kaufman & Bard, 1999 Academic Press

GIT Rotation Cartoon

About the Movie

Please note that this is only a very quick sketch (took 10min). When I have some time I will include a proper labelled movie. Hope this is of some help. You can step through the images using the left-hand controls.

View from left hand side of embryo facing left. Sequence spans approx 6-11 weeks of development. There is an initial 90 degree rotation followed by 2 more 90 degree rotations to give 270 degrees total. The upper GIT is shader light green, the red vessel is the superior mesenteric artery off the dorsal aorta.

Glossary of Terms

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