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Circle of Willis

The circulus arteriosus of Willis forms a polygonal anastomotic channel between two internal carotid and two vertebral arteries. The circle is formed by:-
  1. In front: Anterior communicating artery.
  2. Anterolaterally: Two anterior cerebral artery.
  3. Laterally: Proximal segments of both internal carotid arteries.
  4. Postero-laterally: Two posterior communicating arteries.
  5. Behind: Proximal segments of both posterior cerebral arteries, arising at bifurcating terminal of basilar artery.

Arterial supply of different areas

Cerebral cortex

  1. Cerebral cortex is supplied by branches of all three cerebral arteries.
  2. All the three surface receive branches from all three arteries.
  3. But each surface is supplied predominantly by one artery :-
    1. Middle cerebral artery is main artery on superolateral surface.
    2. Anterior cerebral artery is chief artery on medial surface.
    3. Posterior cerebral artery is main artery on inferior surface.






Other parts


Blood supply of other parts of brain

Part of brain

Blood supply


 Superior cerebellar artery (branch of basilar artery)

 Anterior inferior cerebellar artery (branch of basilar artery)

 Posterior inferior cerebellar artery (branch of vertebral artery)


 Vertebral artery through following branches :-

 Anterior spinal

 Posterior spinal

 Posterior inferior cerebellar artery

 Direct medullary branches

 Basilar artery


 Basilar artery through following branches


 Short and long circumferential

 Superior cerebellar & Anterior inferior cerebellar


 Posterior cerebral artery

 Superior cerebral artery

 Basilar artery


 Posterior communicating artery

 Basilar artery

 Posterior cerebral artery

Internal capsule

Has been explained previously.

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