Arteries of the brain. Computer graphic showing the base of the brain (blue), and the arteries (red) which serve it. The anterior of the brain is at top. The brain is an organ richly supplied with blood vessels; arteries provide it with oxygenated blood. The brain consists largely of two cerebral hemispheres, with the cerebellum outlined at lower frame. Arteries form a circle (upper centre) at the junction where two carotid arteries (cut ends) bring blood from the heart. Cerebral arteries branch off this circle to parts of the cerebrum. At lower centre is a thick basilar artery formed from two vertebral arteries; the basilar artery supplies the cerebellum, brainstem and cerebrum.