Which artery does NOT directly supply the Circle of Willis?

Which artery does NOT directly supply the Circle of Willis?

• A. Posterior cerebral arteries
• B. Internal carotid arteries
• C. Vertebral arteries
• D. Anterior cerebral arteries

Answer: (C)

The Circle of Willis is a circular arterial network at the base of the brain that is formed mainly by the internal carotid arteries and the posterior circulation connecting through the posterior communicating arteries and the posterior cerebral arteries. The vertebral arteries do not enter the circle as direct contributors; instead, they merge to form the basilar artery, which then gives rise to the posterior cerebral arteries that become part of the circle’s posterior portion. So, while the vertebral arteries support the posterior circulation, they do not directly supply the Circle of Willis.

The Circle of Willis is a circular arterial network at the base of the brain that is formed mainly by the internal carotid arteries and the posterior circulation connecting through the posterior communicating arteries and the posterior cerebral arteries. The vertebral arteries do not enter the circle as direct contributors; instead, they merge to form the basilar artery, which then gives rise to the posterior cerebral arteries that become part of the circle’s posterior portion. So, while the vertebral arteries support the posterior circulation, they do not directly supply the Circle of Willis.