Midsagittal section of the deep brain anatomy. This midline view demonstrates the third ventricle, with its roof formed by the body and column of the fornices and the velum interpositum. In the midline anteriorly, the lamina terminalis, optic chiasm and pituitary infundibulum are visible. The floor of the third ventricle is composed of the tuber cinereum of the hypothalamus, the mamillary bodies, and the midbrain tegmen. The inferior sagittal sinus can be seen draining into the straight sinus along with the Vein of Galen, formed by the paired internal cerebral veins and basal veins of Rosenthal. The splenium, body, genu and rostrum of the corpus callosum form the roof of the lateral ventricles as they carry commissural fibers across hemispheres. The midline basilar artery is visible ventral to the pons and midbrain and inferior to the mamillary bodies. Orbitofrontal and frontopolar arteries are branches of the anterior cerebral arteries that are visible here. (Image courtesy of AL Rhoton, Jr.)