Inclusive Anatomy
Structure:
The cerebral arterial circle is an anastomosis of vessels formed by the two vertebral arteries, the basilar artery, and the two internal carotid arteries. The arteries connect to form a circle, which is located on the inferior surface of the brain, near the pituitary gland and the optic chiasm.[1] Anteriorly, the left and right internal carotid arteries give rise to the left and right anterior cerebral arteries, which connect across the midline via the anterior communicating artery. Posteriorly, the left and right vertebral arteries join to form the basilar artery. The basilar artery branches into a left and right posterior cerebral artery. The posterior cerebral arteries complete the circle by connecting to the left and right internal carotid arteries via the left and right posterior communicating arteries.[2]
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Function:
The cerebral arterial circle maintains the brain's blood supply and ensures a constant flow of oxygen and nutrients. The connection of these arteries is such that it provides redundancy in blood supply to the brain. If one of these arteries becomes blocked or compromised, the cerebral arterial circle can help maintain blood flow through alternative pathways, reducing the risk of brain damage due to inadequate blood supply. Clinically, it is estimated that 85% of all intracranial aneurysms occur in this circle.[3]
References:
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Moore, Keith L., et al. Clinically Oriented Anatomy. 7th ed, Wolters Kluwer/Lippincott Williams & Wilkins Health, 2010.
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Fenrich M, Habjanovic K, Kajan J, Heffer M. The circle of Willis revisited: Forebrain dehydration sensing facilitated by the anterior communicating artery: How hemodynamic properties facilitate more efficient dehydration sensing in amniotes. BioEssays. 2021;43(2):2000115. doi:10.1002/bies.202000115
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Schievink WI, Raissi SS, Maya MM, Velebir A. Screening for intracranial aneurysms in patients with bicuspid aortic valve. Neurology. 2010;74(18):1430-1433. doi:10.1212/WNL.0b013e3181dc1a7a
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