Which vessels supply the brain's posterior circulation before forming the basilar artery?

Which vessels supply the brain's posterior circulation before forming the basilar artery?

• A. Vertebral arteries
• B. Facial arteries
• C. External carotid arteries
• D. Internal jugular veins

Answer: (A)

The posterior circulation of the brain is provided by the vertebral arteries, which arise from the subclavian arteries and ascend through the cervical vertebrae to enter the skull. They come together at the level of the brainstem to form the basilar artery, creating the vertebrobasilar system that supplies the brainstem, cerebellum, and posterior cerebral regions. From the basilar artery, the posterior cerebral arteries branch off to reach the occipital lobes and other structures. So, before the basilar artery is formed, the vertebral arteries are the vessels carrying blood to the brain’s posterior circulation. The other vessels listed do not supply the brain’s posterior circulation: facial and external carotid arteries serve facial/scalp regions, and internal jugular veins are venous drainage pathways.

The posterior circulation of the brain is provided by the vertebral arteries, which arise from the subclavian arteries and ascend through the cervical vertebrae to enter the skull. They come together at the level of the brainstem to form the basilar artery, creating the vertebrobasilar system that supplies the brainstem, cerebellum, and posterior cerebral regions. From the basilar artery, the posterior cerebral arteries branch off to reach the occipital lobes and other structures. So, before the basilar artery is formed, the vertebral arteries are the vessels carrying blood to the brain’s posterior circulation. The other vessels listed do not supply the brain’s posterior circulation: facial and external carotid arteries serve facial/scalp regions, and internal jugular veins are venous drainage pathways.