Your brain is incredibly demanding. Despite making up only about 2% of your body weight, it consumes roughly 20% of the oxygen and calories you take in. To fuel its constant activity, from thinking and feeling to controlling your movements, it requires a continuous, reliable supply of blood. Even a brief interruption can cause serious problems.

This vital task is handled by a complex network of blood vessels known as the cerebral circulation. Let's look at how this system is structured to keep your brain running smoothly.

Blood begins its journey to the brain from the heart, traveling through large arteries in your neck. Four main arteries act as the primary pipelines:

• Two internal carotid arteries: One on each side of your neck, these are major vessels that branch off the common carotid arteries. You can sometimes feel their pulse on the side of your neck. They supply the front and middle parts of your brain.
• Two vertebral arteries: These smaller arteries run up the back of your neck, protected by the vertebrae. They primarily supply the back of the brain, including the brainstem and cerebellum.

Once inside the skull, the two vertebral arteries join together to form a single, larger vessel called the basilar artery. Together, the internal carotid arteries and the basilar artery form the main sources of blood for the entire cerebrum.

At the base of the brain, these major arteries don't just stop. They connect in a circular arrangement called the Circle of Willis. Think of it as a traffic roundabout for blood. This structure is a critical safety feature of the brain's circulatory system.

The primary job of the Circle of Willis is to provide multiple paths for blood to reach all parts of the brain. The main arteries—the internal carotids and the basilar artery—all feed into this circle. From this ring, smaller arteries branch off to supply different brain regions.

This remarkable piece of natural engineering ensures that the brain's blood supply remains as stable as possible, protecting the delicate nerve cells that depend on it. It’s a key reason why the brain can withstand minor disruptions in blood flow without immediate damage.

Now that we understand the overall structure, we can begin to look at the specific arteries that branch off from this system to supply critical areas of the brain.