The circle of willis is the vital blood transportation system of brain. It is comprised of arteries that sit on the base of the brain, and its provides communication between the blood supply of the forebrain and hindbrain. The anterior half is formed when the interal carotid artery (ICA) enters the cavity bilaterally and devides into the anterior cerebral artery (ACA) and middle cerebral artery (MCA). The ACA is the united by the anterior communation (ACOM) aretery. Posteriolly, the basilar artery are the formed by the left and right vertebral arteries, branching into the left and right posterior cerebral artery (PCA) and forming the posterior circulation.
