What term refers to the structure at the base of the brain where the anterior, middle, and posterior cerebral arteries meet?

• A. Circle of Willis
• B. Circle of Vieussens
• C. Circle of Sylvius
• D. Circle of Connex

Answer: (A)

The structure at the base of the brain that forms a ring where the anterior, middle, and posterior cerebral arteries meet is the Circle of Willis. This circular network connects the internal carotid systems with the basilar system, formed by the two anterior cerebral arteries joined by the anterior communicating artery, and the posterior circulation connected through the posterior communicating arteries to the posterior cerebral arteries. Its main significance is providing collateral blood flow—if one major artery narrows or blocks, other routes can help sustain cerebral perfusion. The other terms aren’t the standard name for this arterial circle: some are historical or refer to different regions, and they don’t describe this brain vascular ring.