How is the neural tube formed?
Beginning around the 18th gestational day, a midline notochordal thickening anterior to the blastopore forms the neural plate.
A midsagittal groove called the neural groove appears in the plate, and the sides elevate to form the neural folds.
As the folds fuse, the neural tube is formed. Some cells at the edges of the fold do not fuse into the tube and become neural crest cells.
