circle of Willis

arteries supplying the brain

The main arteries supplying the brain, seen looking up from the base of the brain. The circle of Willis is the circular arrangement of blood vessels near the center of the diagram.

The circle of Willis is a circular arrangement of large blood vessels on the undersurface of the brain formed by linked branches of the arteries that supply the brain; it is named after the English anatomist T. Willis (1621–1675). Most cerebral aneurysms occur on or near the circle of Willis.