ANATOMY - PERFUSION

Question 1

Describe the blood supply to the brain. Indicate which vessels form the anterior and posterior cerebral circulation. May use a well labelled diagram (8)

Answer 1

Blood supply according to the circle of Willis and name the main branches

The brain receives blood from two sources: the internal carotid arteries, which arise at the point in the neck where the common carotid arteries bifurcate, and the vertebral arteries. This is the so-called anterior and posterior cerebral circulation. The internal carotid arteries branch to form two major cerebral arteries, the anterior and middle cerebral arteries.

Vertebral arteries join to form the basilar artery and supply cerebellum and the brainstem, ending as the posterior cerebral arteries (left and right).

Question 2

Using a short summary or flow diagram, describe the posterior circulation of the brain, how it is formed, its course, the structures supplied and how it unifies with the anterior circulation of the brain (9)

Answer 2

Vertebral a/s fuse to form the basilar a.
Basilar a. runs superiorly over pons.
Basilar a. bifurcates to form the PCA.
PICA from vertebral a. supplying inf surface of the cerebellum
AICA from basilar a. supplies ant surface of the cerebellum
Sup cerebellar from basilar a. supplies sup surface of cerebellum
Pontine arteries supplies pons
Labyrinthine a supplies inner ear
P Comm unifies post circulation with ant circulation

Question 3

Briefly describe the arterial supply to the occipital lobe of the brain. May use a diagram (5)

Answer 3

Arterial cerebral circle – L & R posterior cerebral arteries arising from the posterior half of the circle. These run caudally to supply the occipital lobe medially, inferiorly, caudally, superiorly, and a small portion laterally.

Question 4

Describe how the deeper structures of the cerebral hemispheres receive their arterial blood supply. May use a labelled diagram (9)

Answer 4

Brief overview of the arterial circle of the cerebrum (Circle of Willis) (4) and then describe the anterior and posterior perforate substance (2) where these end arteries (1) penetrate the brain – central/ ganglionic/ lenticulostriate/ lacunar (2)

Located within the basal forebrain, the anterior perforated substance is a quadrilateral area of grey matter positioned posterior to the gyrus rectus and olfactory trigone and anterolateral to the optic tract. It is bounded medially by the optic chiasm and laterally by the lateral olfactory striae.

Question 5

Cerebral vascular accidents may involve any of the arteries supplying the brain. Most often, however, only one of the three main vessels of the brain is affected. State which one of these main vessels supplies the largest surface area of the cerebral cortex and give the origin of this vessel (3)

Answer 5

MCA - lateral surface of the brain

Question 6

Give two examples of functional losses if the arterial supply to the caudal region of one of the occipital lobes becomes obstructed (2)

Answer 6

Visual cortex at caudal pole of occipital lobe – all special sensation (vision) from the opposite field of vision is lost.

Visual association area surrounds visual cortex – interpreting what is seen – loss.