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Encyclopedia > Circle of Willis
Artery: Circle of Willis
Schematic representation of the circle of Willis, arteries of the brain and brain stem.
The brain and the arteries of the base of the brain. The temporal pole of the cerebrum and a portion of the cerebellar hemisphere have been removed on the right side. Inferior aspect (viewed from below).
Latin circulus arteriosus cerebri
Gray's subject #147 574
MeSH Circle+of+Willis

The circle of Willis (also called the cerebral arterial circle or arterial circle of Willis) is a circle of arteries that supply blood to the brain. It is named after Thomas Willis (1621-1673), an English physician.[1] Image File history File links No higher resolution available. ... Mostly enveloped by the cerebrum and cerebellum (blue), the visible part of brainstem is shown in black. ... Image File history File links Download high-resolution version (600x681, 186 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Circle of Willis Wikipedia:Grays Anatomy images with missing articles 11 Cerebral circulation Posterior communicating artery List... For more specific information about the human brain, see its main article at human brain A sketch of the human brain by artist Priyan Weerappuli, imposed upon his sketch of the profile of Michaelangelos David In animals, the brain, or encephalon (Greek for in the head), is the control... The temporal lobes are part of the cerebrum. ... For other articles about other subjects named brain see brain (disambiguation). ... Figure 1a: A human brain, with the cerebellum in purple. ... Latin is an ancient Indo-European language originally spoken in Latium, the region immediately surrounding Rome. ... Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. ... Section of an artery For other uses, see Artery (disambiguation). ... For more specific information about the human brain, see its main article at human brain A sketch of the human brain by artist Priyan Weerappuli, imposed upon his sketch of the profile of Michaelangelos David In animals, the brain, or encephalon (Greek for in the head), is the control... Thomas Willis Thomas Willis (1621-1673) was an English physician who played an important part in the history of the science of anatomy and was a co-founder of the Royal Society (1662). ... 1621 was a common year starting on Friday of the Gregorian calendar (or a common year starting on Monday of the 10-day slower Julian calendar). ... 1673 (MDCLXXIII) was a common year starting on Sunday of the Gregorian calendar (or a common year starting on Wednesday of the 10-day slower Julian calendar). ... Motto: (French for God and my right) Anthem: God Save the King/Queen Capital London (de facto) Largest city London Official language(s) English (de facto) Unification    - by Athelstan AD 927  Area    - Total 130,395 km² (1st in UK)   50,346 sq mi  Population    - 2006 est. ... The Doctor by Samuel Luke Fildes This article is about the term physician, one type of doctor; for other uses of the word doctor see Doctor. ...

Contents

Components

The basilar artery and middle cerebral arteries, though they supply the brain, are not considered part of the circle.[2] The anterior cerebral artery supplies oxygen to most medial portions of frontal lobes and superior medial parietal lobes. ... The arterial circle and arteries of the brain. ... The carotid artery is a major artery of the head and neck that supplies blood to the head and neck. ... The arterial circle and arteries of the brain. ... The arterial circle and arteries of the brain. ... The basilar artery is one of the arteries which the brain supplies with oxygen-rich blood. ... The middle cerebral artery (MCA) is one of the three major paired arteries that supplies blood to the brain. ...


Physiologic significance

The arrangement of the brain's arteries into the Circle of Willis creates redundancies in the cerebral circulation. If one part of the circle becomes blocked or narrowed (stenosed) or one of the arteries supplying the circle is blocked or narrowed, blood flow from the other blood vessels can often preserve the cerebral perfusion well enough to avoid the symptoms of ischemia.[3] A stenosis is an abnormal narrowing in a blood vessel or other tubular organ or structure. ... The arterial system The blood vessels are part of the circulatory system and function to transport blood throughout the body. ... In medicine, ischemia (Greek ισχαιμία, isch- is restriction, hema or haema is blood) is a restriction in blood supply, generally due to factors in the blood vessels, with resultant damage or dysfunction of tissue. ...


Anatomic variation

Considerable anatomic variation exists in the circle of Willis. The "textbook version" of the circle, based on a series of 1413 brains, is only seen in 34.5% of cases.[4]


Subclavian steal and the circle of Willis

The redundancies that the circle of Willis introduce can also lead to reduced cerebral perfusion.[5][6] In subclavian steal syndrome, which results from a proximal stenosis (narrowing) of the subclavian artery (a vessel that supplies a vessel that feeds the circle of Willis), blood is "stolen" from the circle of Willis to preserve blood flow to the upper limb. In medicine, subclavian steal syndrome (SSS), also subclavian steal phenomenon and subclavian steal steno-occlusive disease, is a constellation of signs and symptoms that arise from retrograde (reversed) vertebral artery (blood) flow due to a proximal subclavian artery stenosis (narrowing) and/or occlusion. ... In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ... A stenosis is an abnormal narrowing in a blood vessel or other tubular organ or structure. ... The subclavian artery is a major artery of the upper thorax that mainly supplies blood to the head and arms. ... In humans, the upper limb is an anatomical term for the limb that is attached to the pectoral girdle. ...


Origin of arteries

The left and right internal carotid arteries arise from the right and left common carotid arteries. Left Common Carotid Artery- One of three arteries that originate along the aortic arch. ...


The Posterior Communicating Artery is given off as a branch of the Internal Carotid Artery just before it divides into its terminal branches - the Anterior and Middle Cerebral Arteries. The Anterior Cerebral Artery forms the anterolateral portion of the Circle of Willis, while the Middle Cerebral Artery does not contribute to the Circle.


The right and left posterior cerebral arteries arise from the basilar artery, which is formed by the left and right vertebral arteries. The vertebral arteries arise from the subclavian arteries. The arterial circle and arteries of the brain. ... The basilar artery is one of the arteries which the brain supplies with oxygen-rich blood. ... The vertebral arteries are branches of the subclavian arteries. ... The vertebral arteries are branches of the subclavian arteries. ... The subclavian artery is a major artery of the upper thorax that mainly supplies blood to the head and arms. ...


The anterior communicating artery connects the two anterior cerebral arteries and could be said to arise from either the left or right side. The arterial circle and arteries of the brain. ...


All arteries involved give of cortical and central branches. The central branches supply the interior of the Circle of Willis, more specifically, the Interpeduncular fossa. The cortical branches are named for the area they supply. Since they do not directly affect the Circle of Willis, they are not dealt with here.


As people age the circle of Willis enlarges. This improvement in collateral circulation is why strokes generally affect children more severely than the elderly.


References

  1. ^ Uston C. Dr. Thomas Willis' famous eponym: the circle of Willis. J Hist Neurosci. 2005 Mar;14(1):16-21. PMID 15804755. Free Full Text.
  2. ^ Moore KL, Dalley AR. Clinically Oriented Anatomy, 4th Ed., Lippincott Williams & Wilkins, Toronto. Copyright 1999. ISBN 0-683-06141-0.
  3. ^ "Spect measurements of regional cerebral perfusion and carbondioxide reactivity: Correlation with cerebral collaterals in internal carotid artery occlusive disease.". J Neurol. PMID 17063318. 
  4. ^ Bergman RA, Afifi AK, Miyauchi R, Circle of Willis. Illustrated Encyclopedia of Human Anatomic Variation, URL: http://www.anatomyatlases.org/AnatomicVariants/Cardiovascular/Text/Arteries/CircleofWillis.shtml. Accessed on November 6, 2005.
  5. ^ Klingelhofer J, Conrad B, Benecke R, Frank B. Transcranial Doppler ultrasonography of carotid-basilar collateral circulation in subclavian steal. Stroke. 1988 Aug;19(8):1036-42. PMID 3041649.
  6. ^ Lord RS, Adar R, Stein RL. Contribution of the circle of Willis to the subclavian steal syndrome. Circulation. 1969 Dec;40(6):871-8. PMID 5377222.

External links

A cadaver is a dead body. ... North Harris College is a public community college, located in Houston, Texas offering Associates degrees and program certifications in over 60 fields of study. ...

Additional images


  Results from FactBites:
 
Circle of Willis - Wikipedia, the free encyclopedia (717 words)
Schematic representation of the circle of Willis, arteries of the brain and brain stem.
If one part of the circle becomes blocked or narrowed (stenosed) or one of the arteries supplying the circle is blocked or narrowed, blood flow from the other blood vessels can often preserve the cerebral perfusion well enough to avoid the symptoms of ischemia.
Contribution of the circle of Willis to the subclavian steal syndrome.
circle of Willis: Definition and Much More from Answers.com (668 words)
The circle of Willis (also called the cerebral arterial circle or arterial circle of Willis) is a circle of arteries that supply the brain.
If any one of the arteries in the circle become blocked or narrowed (stenosed) or one of the arteries supplying the circle is blocked or narrowed, blood flow from the other blood vessels can usually maintain cerebral perfusion.
In subclavian steal syndrome, which results from a proximal stenosis (narrowing) of the subclavian artery (a vessel that supplies a vessel that feeds the circle of Willis), blood is "stolen" from the circle of Willis to preserve blood flow to the upper limb.
  More results at FactBites »

 
 

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