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•  The neural tube of embryonic chordates is formed by infolding of ectoderm followed by elongation of the tube

The development of a fully-formed organism from a fertilised egg is called embryogenesis

  • All tissues are derived from three initial germ layers (ectoderm, mesoderm, endoderm) formed via gastrulation
  • In chordates, a flexible notochord will develop during gastrulation and lead to the subsequent formation of a neural tube

The formation of a neural tube in embryonic chordates occurs via the process of neurulation

  • Cells located in the outer germ layer (ectoderm) differentiate to form a neural plate
  • The neural plate then bends dorsally, folding inwards to form a groove flanked by a neural crest
  • The infolded groove closes off and separates from the neural crest to form the neural tube
  • The neural tube will elongate as the embryo develops and form the central nervous system (brain and spinal cord)
  • The cells of the neural crest will differentiate to form the components of the peripheral nervous system

Overview of Neurulation


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•  Annotation of a diagram of embryonic tissues in Xenopus, used as an animal model, during neurulation

Xenopus are a genus of frog that possess robust embryos that can tolerate extensive manipulation

  • This makes them a suitable animal models for investigating the developmental stages of embryogenesis

During neurulation, the following embryonic tissues should be easily identifiable:

  • Three germ layers (outer = ectoderm ; middle = mesoderm ; inner = endoderm)
  • A hollow cavity called the archenteron (will develop into the digestive tract)
  • Notochord (flexible rod that stimulates neurulation)
  • Neural tube (developed from the infolding of the neural plate)

Neurulation in a Xenopus Embryo

                            Data:         Embryo Cross-Section            Structure-Function Relationship