The vertebral arteries join to form which artery?

• A. Internal Carotid Arteries
• B. External Carotid Arteries
• C. Anterior Cerebral Arteries
• D. Vertebral Arteries

Answer: (D)

The key idea is how the posterior circulation is formed. The two vertebral arteries travel up through the neck and enter the skull, where they join to form a single vessel along the ventral surface of the brainstem—the basilar artery. The basilar artery then runs upward and typically splits into the posterior cerebral arteries, contributing to the brain’s posterior circulation.

The other arteries listed are not formed by the vertebral arteries: the internal and external carotid arteries are part of the carotid system and primarily feed the anterior circulation, while the anterior cerebral arteries are branches of the internal carotid system. So, the vessel produced by the joining vertebral arteries is the basilar artery, not the vertebral arteries themselves.