Brent Cornell

    
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

    
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