neural tube formation, the various processes and stages involved in the embryonic development of the neural tube, which subsequently differentiates into the brain, the spinal cord, and other neural tissue of the central nervous system. The primitive tube originates from a flat, single layer of ectodermal tissue that extends longitudinally along the middorsal line of the embryonic disk from the area of the primitive streak forward to the cephalic extremity. This tissue, the neural plate, grows rapidly and becomes thickened, resulting in the invagination and formation of a hollow groove, the neural groove. With continued cell division the groove becomes deeper, and the folds thicken so that they eventually meet and fuse, converting the neural groove into the neural tube. The closing of the neural tube progresses toward both the caudal and the cephalic regions. At the cephalic end the tube expands into a large vesicle with three subdivisions that differentiate into the forebrain (prosencephalon), the midbrain (mesencephalon), and the hindbrain (rhombencephalon). The epithelium of the wall of the tube develops into the various cells of the nervous system. The caudal part of the tube subsequently forms the spinal cord. Failure of any part of the neural tube to close during early embryonic development results in a number of congenital defects. See also neural tube defect.
