Midsagittal section of the third ventricle and surrounding deep brain anatomy. This midline view demonstrates the roof of the third ventricle formed by the fornices, coursing with the internal cerebral veins. In the midline, the lamina terminalis, optic chiasm and pituitary infundibulum are visible and border the third ventricle anteriorly. The splenium, body, genu and rostrum of the corpus callosum are visible along with the pericallosal branch of the anterior cerebral artery. The floor of the third ventricle is composed of the tuber cinereum of the hypothalamus, the mammillary bodies, and the midbrain tegmen. The inferior sagittal sinus can be seen draining into the straight sinus along with the Vein of Galen. (Image courtesy of AL Rhoton, Jr.)