Illustration of the blood supply to the brain with a close-up view of the Circle of Willis and the major arteries of the brain. The circle of Willis includes the anterior cerebral, middle cerebral, anterior communicating, posterior communicating, and the posterior cerebral arteries. The major arteries of the brain encompass the anterior cerebral, middle cerebral, anterior communicating, posterior communicating, basilar, posterior cerebral, internal carotid, and vertebral arteries.