The vertebral and the carotid artery nourish a collection of blood vessels called the circle of Willis. The carotid artery supplies blood to most of the cerebral hemispheres. It runs up the lateral sides of the neck, then splits into the anterior cerebral artery and the middle cerebral artery. The anterior cerebral artery supplies blood to the medial surface of the frontal and parietal lobes as well as the corpus callosum. The middle cerebral artery supplies the lateral portions of the hemispheres and has branches that supply internal structures, like the basal ganglia and internal capsule. Before the anterior and middle cerebral arteries split, the blood branches out to supply structures, such as pituitary gland, the eye and optic tract, the
