What is "neurula"

Neurula \Neu"ru*la\, n. [NL., dim. of Gr. ney^ron a nerve.] (Zo["o]l.) An embryo of certain invertebrates in the stage when the primitive band is first developed.

n. (context zoology English) An embryo of vertebrates in the stage when the primitive band is first developed.

A Neurula is an embryo at the early stage of development in which neurulation occurs.

Neurulation is the development of the nervous system in the vertebrates, at the thickened area above the notochord in ectoderms. The neural plate will fold to produce the neural tube which will develop into the brain. Remaining tissue will develop into the spinal cord. Neurula involves the formation of an internal neural tube from an external sheet of cells. The first signs of neurulation are flattening and thickening of the ectoderm overlying the notochord; this thickened area forms a neural plate. The edges of the neural plate that run in an anterior-posterior direction continue to thicken, forming ridges or folds. Between these neural folds, a groove forms and deepens as the folds roll over it to converge on the midline. The fold fuses, forming a cylinder--the neural tube--and a continuous overlying layer of epidermal ectoderm. The neural tube develops bulges at the anterior end, which become the major divisions of the brain. The remaining sections of the tube becomes the spinal cord.