Arteries at the base of the brain. Illustration showing the branching patterns of the internal carotid (from the common carotid) and vertebral arteries (from the subclavian) supplying the base of the brain. In the centre, surrounding the pituitary/hypophyseal region, the arteries from left and right join together to form the arterial circle of Willis. From Sobotta, J. (1906) Atlas der deskriptiven Anatomie des Menschen. Vol.3, Lehmann, Munich.