True regarding cavity of diencephalons is
D i.e. Inter thalamic adhesions join lateral Walls Lamina terminalis is a thin sheet of gay matter, which extend between two hemisphere from rostrum of corpus callosum to top of optic chiasma forming the anterior wall of 3rd ventricle. Septum pellucidum is a thin veical sheet of (gray & white) nervous tissue, which connects corpus callosum (rostrum, genu & front of body) to anterior column of fornix and forms paition between anterior horns of lateral venticles (not 3rd ventricle or cavity of diencephalon). Lateral wall of cavity of diancephalon (3rd ventricle) is formed by thalmus, hypothalmus, hypothalmic sulcus & subthalmus.
Septum pellucidum forms paition
Septum pellucidum cavity opens superiorly
Lateral wall is lamina terminalis
Inter thalamic adhesions join lateral walls