Frog - Neurula

Formation and closure of neural plate is called Neurulation and the embryo at the time of neurulation is called Neurula. Therefore, during this stage, it posses distinguished neural plate and neural tube. After the closure of blastopore, the neurectoderm situated along the mid-dorsal portion of gastrula is called neural plate. Lateral margin of neural plate become thickened and elevate above general level as neural folds. As a result, a groove forms, called neural groove. Gradually neural folds grow inward towards one another and fuse to form neural tube with a cavity called neurocoel. At the anterior end, neural folds remain unfused leaving an opening called neuropore. Which closes later. Neural folds in posterior end merge with the sides of blastopore enclosing blastopore. By this, blastopore act as temporary passage between neurocoel and archenteron called neurenteric canal. Finally lateral epiderm grow over neural tube and fuses so that neural tube gets segregated.

Development of neural tube is induced by chordamesoderm which is called as the primary organizer by Spemann. When neural tube separates from ectoderm, some cells move out to occupy the space between neural tube and epiderm as a peripheral band called as neural crest. Anterior end of neural tube develops to brain and posterior end develops to spinal cord. Cells above the archenteron rearrange themselves to form notochord.