Willis

Willis may refer to several topics, but in the context of medicine, it is most commonly associated with the Circle of Willis, a part of the circulatory system in the brain.

Circle of Willis

The Circle of Willis (also called Willis' Circle, loop of Willis, or circulus arteriosus cerebri) is a circulatory anastomosis that supplies blood to the brain and surrounding structures. It is named after Thomas Willis (1621–1675), an English doctor who was a founding member of the Royal Society.

Structure

The Circle of Willis is a part of the cerebral circulation and is composed of the following arteries:

• Anterior cerebral artery
• Anterior communicating artery
• Internal carotid artery
• Posterior cerebral artery
• Posterior communicating artery

These arteries form a circle of blood vessels that supply blood to the brain. The Circle of Willis is located at the base of the brain.

Function

The Circle of Willis provides a critical role in the cerebral circulation. It is a part of the blood–brain barrier, a protective mechanism that prevents substances from the bloodstream from entering the brain. The Circle of Willis also provides a backup circulation to the brain if one of the main arteries is blocked or narrowed (stenosis).

Clinical significance

Abnormalities of the Circle of Willis can lead to a number of medical conditions, including:

• Stroke
• Aneurysm
• Subarachnoid hemorrhage

See also

• Cerebrovascular disease
• Neuroanatomy

External links

• Circle of Willis: Anatomy at PubMed Health

Willis Resources
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