Blood supply to optic chiasm and pituitary gland.  Coronal section through the frontal lobe at the level of the optic chiasm.  The two optic nerves converge at midline to undergo a partial decussation within the optic chiasm.  The anterior cerebral arteries (ACAs) are located immediately dorsal to the optic chiasm and supply penetrating branches (not seen in this dissection) to the chiasm.  The left and right anterior cerebral arteries are joined at the midline by a stout anterior communicating artery.  The pituitary stalk attaches to the inferior surface of the hypothalamus just caudal to the optic chiasm.  The anterior pituitary receives its blood supply from the superior hypophyseal artery, a branch of the internal carotid artery.  The proximal portion of the ACA gives origin to the recurrent artery of Heubner (medial striate artery), visible only on the right side of the image. (Image courtesy of AL Rhoton, Jr.)