2020–2021 BCSC Basic and Clinical Science Course™
2 Fundamentals and Principles of Ophthalmology
Part I: Anatomy
Chapter 3: Cranial Nerves: Central and Peripheral Connections
The Cerebral Vascular System
Circle of Willis
The major arteries supplying the brain are the right and left ICAs (which distribute blood primarily to the rostral portion of the brain, anterior circulation) and the right and left vertebral arteries (which join to form the basilar artery, posterior circulation). The basilar artery distributes blood primarily to the brainstem and the posterior portion of the brain. These arteries interconnect at the base of the brain at the circle of Willis, also called the cerebral arterial circle (Figs 3-27, 3-28; see also Figs 3-3, 3-16). These interconnections (anastomoses) help distribute blood to all regions of the brain, even when a portion of the system becomes occluded. CN III, in particular, can be affected by vascular lesions within this region.
Excerpted from BCSC 2020-2021 series: Section 2 - Fundamentals and Principles of Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.