The structure indicated is the anterior communicating artery.

The anterior communicating artery connects the left cerebral artery to the right cerebral artery. It is one of the blood vessels which contributes to the arterial Circle of Willis – an anastomosis of arterial vessels located on the base of the brain, consisting of the following arteries:

• Anterior cerebral artery
• Anterior communicating artery
• Internal carotid artery
• Posterior cerebral artery
• Posterior communicating artery

The anterior cerebral artery also gives rise to small collateral vessels which supply the frontal lobes and basal forebrain. This vessel is a common site for the formation of aneurysms. Saccular aneurysms, known as berry aneurysms are round outpouchings of the vessel wall and the anterior communicating artery is the most common site for these types of aneurysm to form. Rupture of these aneurysms leads to haemorrhage into the subarachnoid space.

Learn more about the Circle of Willis in this tutorial!