The neural tube is the embryonic structure that ultimately forms the brain and spinal cord. The neural tube is formed during a process called neurulation, which begins when the underlying dorsal mesoderm signals the ectodermal cells above it to elongate into columnar neural plate cells. The edges of the neural plate thicken and migrate toward the midline of the embryo and their eventual fusion at the dorsal midline creates the hollow neural tube.
Neurulation starts at E8 in mouse, and on day 20 in human. The neural tube is completely closed by approximately E10.5 in mouse, and day 29 in human. An initial anterior-posterior patterning can be seen even before neural tube closure, with four distinct regions of the neural tube: the prosencephalon (forebrain), mesencephalon (midbrain), rhombencephalon (hindbrain) and the future spinal cord.