Circle of Willis

1. CEREBRAL ARTERIAL CIRCLE
PRESENTED BY: VIVEK

2. There are two paired arteries which are responsible for
the blood supply to the brain:
1. The vertebral arteries
2. The internal carotid arteries.
These arteries arise in the neck, and ascends to the
cranium.
Within the cranial vault the terminal branches of the
arteries forms an anastomotic circle, called “Cerebral
arterial circle”.

3. Internal carotid artery
Vertebral artery

4. Also referred to as:
• The Circle of Willis
• The Loop of Willis
• The Willis polygon
The Circle of Willis is a ring-like arterial structure located at the
base of the brain that supplies blood to the brain and surrounding
structures.

6. There are three main (paired) constituents of the Circle of
Willis:
•Anterior cerebral arteries – terminal branches of the
internal carotid arteries.
•Internal carotid arteries – located immediately proximal
to the origin of the middle cerebral arteries.
•Posterior cerebral arteries – terminal branches of the
vertebral arteries.

7. To complete the circle, two ‘connecting vessels’ are also
present:
•Anterior communicating artery – connects the two
anterior cerebral arteries.
•Posterior communicating artery – branch of the internal
carotid, this artery connects the ICA to the posterior
cerebral artery.

8. Circle of
Willis
Anterior communicating artery
Posterior communicating
artery
Anterior cerebral artery
Internal carotid
arteries
Posterior cerebral
arteries

9. Functions of Circle of Willis
The Circle of Willis is basically an arrangement of interconnected vascular
channels that ensure that the (oxygenated) blood flow to the brain
continues unimpeded, in case any of the principal suppliers are
obstructed by injury, physical pressure or disease.

10. Intracerebral Aneurysms
An aneurysm is a dilation of an artery, which is
greater than 50% of the normal diameter. They are
most likely to occur to occur in the vessels
contributing to the Circle of Willis. They are
particularly dangerous – producing few symptoms
until they rupture. Upon rupture, blood typically
accumulates in the subarachnoid space – with a
subsequent increase in intracranial pressure.
Treatment: Surgical

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