ABSTRACT
The diencephalon, an important part of the central nervous system (CNS) rostral to the brainstem, consists of the thalamus, epithalamus, hypothalamus, and subthalamus. The thalamus and epithalamus are separated from the hypothalamus and subthalamus by the hypothalamic sulcus. The latter sulcus extends between the interventricular foramen of Monro and the cerebral aqueduct. The diencephalon lies between the cerebral hemispheres, caudal to the lamina terminalis. It contains the third ventricle (Figure 7.1), which is bounded superiorly by the ependyma and the pia mater that join together to form the tela choroidea. This ventricle stretches from the lamina terminalis rostrally to the cerebral aqueduct caudally and is connected to the lateral ventricle via the interventricular foramen of Monro and to the fourth ventricle through the cerebral (Sylvian) aqueduct. It extends into
the pineal stalk as the pineal recess and to the area superior the optic chiasma as the optic recess. It is frequently crossed by bers of the interthalamic adhesion (massa intermedia) and also extends into the infundibulum as a funnel-shaped infundibular recess. The cerebrospinal uid within this ventricle is secreted by the choroid plexus, which is attached to the tela choroidea and is supplied by the posterior choroidal artery.
