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 tickening of the ectoderm overlying the notochord; this thickened area forms a neurual plate. The edges of the neural plate that run an anterior-posterior direction continue to tickening to form ridges or folds. Between these neural folds, a groove forms and deepens as the fold 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, witch become (as said above) the major divisions of the brain; the rest of the tube becomes the spinal cord.