The ventricular spaces in the various subdivisions of the brain reflects the fact that the ventricles are the adult derivatives of the open space of the embryonic neural tube. The two lateral ventricles, situated within the cerebrum, are relatively large and C-shaped, and roughly wraps around the dorsal aspects of the basal ganglia. In the lateral ventricles of the embryo the successive generation of neurons gives rise to the 6-layered structure of the neocortex, constructed from the inside out during development.
The third ventricle forms a narrow midline cavity between the right and left thalamus, communicating with the lateral ventricles through a small opening at the anterior end of the third ventricle. The third ventricle is continuous caudally with the cerebral aqueduct, which runs though the midbrain. At its caudal end, the aqueduct opens into the fourth ventricle, a larger space in the dorsal pons and medulla.
The Ventricular System of the Brain