- Circle of Willis (circulus arteriosus): six-sided polygon of arteries at the base of the brain, around the interpeduncular fossa.
- Formed by branches of internal carotid and basilar arteries; contributes most of the brain's arterial supply.
Blood Supply to the Brain: Systems and Circulations
- Brain supplied by 4 arteries in two systems:
- Paired internal carotid arteries (carotid system) via anterior circulation.
- Paired vertebral arteries (vertebral system) via posterior circulation.
Circulation
Anterior
- Share
- about 80%
- Supplies
- Supratentorial structures, cerebrum and diencephalon
Posterior
- Share
- about 20%
- Supplies
- Infratentorial structures, cerebellum and brainstem
- Internal carotid arteries enter the cranial cavity through the carotid canal near the foramen lacerum.
- Vertebral arteries enter through the foramen magnum.