4th June 2023

Blood supply to the brain

The blood supply to the brain is divided into the anterior and posterior segments. These are supplied by two pairs of arteries, the two internal carotid arteries and two vertebral arteries. The internal carotid artery divides to become the anterior and middle cerebral artery. The anterior and middle cerebral arteries supply the anterior segment of the brain.

The two vertebral arteries join in the brainstem to form the basilar artery. This becomes the posterior cerebral artery at the level of the cerebrum. The posterior cerebral artery supplies the posterior segment of the brain.

Blood supply of the brain subdivided by region

Image Sources: 

• Wikimedia Commons (2008). Cerebral vascular territories, Licensed under a creative commons licence. Available for free at: https://en.wikipedia.org/wiki/File:Cerebral_vascular_territories.jpg (Accessed on: 11 January 2023).

• Wikimedia Commons (2008). Cerebral vascular territories midline, Licensed under a creative commons licence. Available for free at: https://en.wikipedia.org/wiki/File:Cerebral_vascular_territories_midline.jpg (Accessed on: 11 January 2023).

There is communication between the anterior and posterior segments at the circle of Willis (see image below). This provides collateral communication between the internal carotid and posterior cerebral arteries.

Circle of Willis

Image Source: Wikimedia Commons (2007). Circle of Willis en, Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:Circle_of_Willis_en.svg (Accessed on: 11 January 2023).