Brain development occurs from the three vesicles of the embryo's neural tube.
By approximately 4.5 to 5 menstrual weeks, the primitive neural plate has developed. The neural plate then divides into the neural crest and the neural tube. The neural tube differentiates into the primitive brain and the spinal cord.
At about 7 to 8 menstrual weeks, the primary vesicles of the brain are formed and can be recognized with endovaginal sonography.
The midbrain links the diencephalon and telecephalon to the rest of the brainstem.