CAMRT Radiography Practice Exam

Which of the following is NOT part of the Circle of Willis?

1. Right and left anterior cerebral arteries

2. Right and left internal carotid arteries

3. Anterior communicating artery

4. Right and left vertebral arteries

The correct answer is: Right and left vertebral arteries

The Circle of Willis is an important arterial structure located at the base of the brain that provides collateral blood flow to the brain. It consists of several key arteries that interconnect to form a circle, ensuring a continuous supply of blood even if one of the main arteries is obstructed. The right and left anterior cerebral arteries, right and left internal carotid arteries, and the anterior communicating artery are all integral parts of the Circle of Willis. These arteries play significant roles in supplying blood to various regions of the brain. In contrast, the right and left vertebral arteries, which are included in the answer choice identified, do not form part of the Circle of Willis. Instead, these vertebral arteries merge to form the basilar artery, which supplies blood to the posterior circulation of the brain. This distinct difference highlights that the vertebral arteries function independently and are not part of the cerebral arterial circle that characterizes the Circle of Willis. Therefore, the presence of the vertebral arteries outside of this structure makes it the correct answer.