Blood Supply
1. Circle of Willis (cerebral arterial circle)
Located just in front of the midbrain, the circle of Willis connects the posterior circulation of the brain, which gets its blood from the vertebral arteries, to the anterior circulation of the brain, getting blood from the internal carotid arteries. There are also several small communicating arteries that complete the circle. Although the circle of Willis includes the arteries that supply blood to the cerebral hemispheres, blood does not normally circulate around it because there is equal pressure in the anterior and posterior circulations.
- 1.Circle of Willis (cerebral arterial circle)
- 2.Anterior cerebral artery (ACA)
- 3.Anterior communicating artery
- 4.Internal carotid artery
- 5.Middle cerebral artery (MCA)
- 6.Posterior communicating artery
- 7.Posterior cerebral artery
- 8.Superior cerebellar artery
- 9.Basilar artery
- 10.Anterior inferior cerebellar artery (AICA)
- 11.Vertebral artery
- 12.Posterior inferior cerebellar artery (PICA)
Location
While the circle of Willis (cerebral arterial circle) is the key to the blood supply of the cerebral hemispheres, a simpler explanation involves the anterior and posterior circulations of the brain.
Blood forming the anterior circulation comes from the internal carotid arteries, which divide into the middle cerebral artery (MCA) and anterior cerebral artery (ACA) on each side of the brain.
Blood forming the posterior circulation comes from the basilar artery, formed by joining of the left and right vertebral arteries, which divides to form the posterior cerebral arteries (PCA).
Circle of Willis
Despite its name, the circle of Willis (cerebral arterial circle) has six sides and is hexagonal. These connected arteries surround the optic chiasm and midbrain at the top of the brainstem on the inferior surface of the brain.
As can be seen in the main Blood Supply image, the two anterior cerebral arteries, two posterior cerebral arteries and two posterior communicating arteries form the sides of the hexagon.
However, blood does not normally flow along these thin posterior communicating arteries and therefore blood does not normally circulate between the anterior circulation of the brain and the posterior circulation of the brain.
As their names suggest, it is the anterior cerebral arteries, the posterior cerebral arteries and the left and right middle cerebral arteries that supply blood to the cerebrum.
