Spina bifida occulta d. The primitive neural tube has three layers a. ventricular layer. Dorsal-ventral differentiation and the emergence of sensory and motor systems a. The choroid plexus produces the CSF iii. The choroid plexus develops from the thin roof of the fourth ventricle and a similarly thin roof of the third ventricle.
Blood vessels invaginate into the ventricular system forming the choroid plexus.