Intracranial blood vessels, rotating coloured 3D axial computed tomography (CT) angiogram scan. The initial view looks down on the head, with the skull shown in cut-away section. The scan shows the arteries (orange) supplying blood inside the cranial cavity. These arteries branch out inside the skull from the internal carotid arteries and the vertebral arteries, supplying oxygenated blood to the brain (removed here). The veins and sinuses of the venous system are also shown. At centre is the circle of Willis.