The cerebral circulation
This is a standard question but one which contains a lot of anatomical detail. It may be helpful to practise drawing a simple explanatory diagram. The viva may be linked to intracranial aneurysms and their management, and it may also touch on physiological aspects of cerebral perfusion, on the problem of cerebral vasospasm or briefly on the subject of intracranial pressure.
You will be asked about the arterial supply to the brain. The venous drainage is included below but is less likely to feature prominently in the oral.
Arterial supply (Figure 2.1)
The brain is supplied by four major vessels: two internal carotid arteries which provide two-thirds of the arterial supply, and the two vertebral arteries which deliver the remaining third. (Some texts quote an 80:20 distribution.)
The vertebral arteries give off the posterior inferior cerebellar arteries, before joining to form the basilar artery. This also provides the anterior inferior cerebellar and the superior cerebellar arteries.
The basilar artery then gives off the two posterior cerebral arteries, which supply the medial side of the temporal lobe and the occipital lobe.
The artery then anastomoses with the carotid arteries via two posterior communicating arteries.
The internal carotid arteries meanwhile give rise to the middle cerebral arteries which supply the lateral parts of the cerebral hemispheres. They also provide much of the supply to the internal capsule, through which pass a large number of cortical afferent and efferent fibres.
The carotids also give rise to the anterior cerebral arteries, which are connected by the anterior communicating artery and which supply the medial and superior aspects of the hemispheres.