Introduction to Circulation

This image shows the circulation regions of the brain.

The anterior circulation is served by the internal carotids, which supply blood to the anterior 3/5 of the cerebrum. The main branches of the internal carotids are the:

• Middle cerebral artery (MCA)

• Anterior cerebral artery (ACA)

The posterior circulation is served by:

• The vertebrobasilar arteries which supply the posterior 2/5 of the cerebrum, part of the cerebellum and the brain stem

• The basilar artery which gives off the posterior cerebral arteries (PCA)

The anterior and posterior circulations are linked via posterior communicating arteries forming the Circle of Willis. The precise area supplied by each artery varies between individuals, as does the presence or absence of collateral vessels.