Blood Supply

The cortex is supplied by the two internal carotid arteries and the two vertebral arteries (Figures IV-10-4 and IV-10-5). On the base (or inferior surface) of the brain, branches of the internal carotid arteries and the basilar artery anastomose to form the circle of Willis. The anterior part of . the circle lies in front of the optic chiasm, whereas the posterior part is situated just below the mammillary bodies. The circle of Willis is formed by the terminal part of the internal carotid arteries; the proximal parts of the anterior and posterior cerebral arteries and the anterior and posterior communicating arteries. The middle, anterior, and posterior cerebral arteries, which arise from the circle of Willis, supply all of the cerebral cortex, basal ganglia, and diencephalon.

Figure IV-10-5.The Distributions of the Cerebral Arteries: II

Figure IV-10-7. Anteroposterior View of Left Internal Carotid

Inferior view

Calculation recognition

Broca area

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Lateral view - Left

Spatial perception

Lateral view - Right

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Medial view

Calculation

Spatial recognition perception

Broca area

Wernicke

Lateral view - Right

Lateral view - Left

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Medial view iT^j Anterior cerebral artery | Posterior cerebral artery | | Middle cerebral artery

Inferior view

Figure lv-10-8. Territories Supplied by the Cerebral Arteries

The posterior cerebral artery is formed by the terminal bifurcation of the basilar artery. The pos terior communicating artery arises near the termination of the internal carotid artery and pass es posteriorly to join the posterior cerebral artery. The posterior communicating arteries com plete the circle of Willis by joining the vertebrobasilar and carotid circulations. The posterior cerebral artery supplies the occipital and temporal cortex on the inferior and lateral surfaces of the hemisphere, the occipital lobe and posterior two thirds of the temporal lobe on the medial surface of the hemisphere, and the thalamus and subthalamic nucleus.

Occlusion of the posterior cerebral artery results m a homonymous hemianopia of the con tralateral visual field with macular sparing.

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