A, Inferior view. The supraclinoid portion of the carotid artery is divided into three segments based on the site of origin of its major branches: the ophthalmic segment extends from the origin of the ophthalmic artery to the origin of the posterior communicating artery; the communicating segment extends from the origin of the posterior communicating artery to the origin of the anterior choroidal artery; and the choroidal segment extends from the origin of the anterior choroidal artery to the bifurcation of the carotid artery. The optic nerves are above the ophthalmic arteries. The optic chiasm and optic tracts are above the anterior and posterior lobes of the pituitary gland. The tuber cinereum is anterior to the apex of the basilar artery. The posterior cerebral arteries pass around the cerebral peduncles above the oculomotor nerves. The perforating branches arising from the ophthalmic segment pass to the anterior lobe, optic nerve, and chiasm and to the anterior part of the tuber cinereum. A single perforating branch arises from the communicating segment on each side and passes upward to the optic tract and the floor of the third ventricle. B, The pituitary gland has been reflected backward to show the superior hypophyseal arteries passing from the ophthalmic segments to the infundibulum. The anterior cerebral and the anterior communicating arteries pass above the optic chiasm. C, Posterior view. The basilar artery and brainstem have been divided and the floor of the third ventricle elevated to provide this posterior view of the arteries in the suprasellar area. The tuber cinereum and mamillary bodies are exposed between the optic tracts. D, The right half of the dorsum and the right posterior clinoid process have been removed to expose the anterior and posterior lobes of the pituitary gland. The basilar, posterior cerebral, and superior cerebellar arteries have been elevated to expose the pituitary stalk and floor of the third ventricle. The inferior hypophyseal and the tentorial arteries arise from the carotid artery. (Images courtesy of AL Rhoton, Jr.)