WordNet

travel around something; "circle the globe"
ellipse in which the two axes are of equal length; a plane curve generated by one point moving at a constant distance from a fixed point; "he calculated the circumference of the circle"
something approximating the shape of a circle; "the chairs were arranged in a circle"
a curved section or tier of seats in a hall or theater or opera house; usually the first tier above the orchestra; "they had excellent seats in the dress circle" (同)dress_circle
any circular or rotating mechanism; "the machine punched out metal circles" (同)round
move in circles (同)circulate
English physician who was a pioneer in the study of the brain (1621-1675) (同)Thomas Willis

PrepTutorEJDIC

『円』 / (劇場などの)半円形のさじき / (…の)円形のもの《+『of』+『名』》 / (活動・勢力などの)範囲 / 《時に複数形で》(共通の利害・活動などで結ばれた)『仲間』,団体,…界 / 一巡;循環 / 『円を描く』,旋回する / …'を'『円で囲む』;…'を'取り囲む / …‘の'回りを回る
《所有・所属》…『の』,…のものである,…に属する・《材料・要素》…『でできた』,から成る・《部分》…『の』[『中の』] ・《数量・単位・種類を表す名詞に付いて》…の・《原因・動機》…『で』,のために(because of) ・《主格関係》…『の』,による,によって・《目的格関係》…『を』,の・《同格関係》…『という』・《関係・関連》…『についての』[『の』],の点で・《抽象名詞などと共に》…の[性質をもつ] ・《『It is』+『形』+『of』+『名』+『to』 doの形で,ofの後の名詞を意味上の主語として》・《分離》…『から』・《起原・出所》…『から』[『の』](out of) ・《『名』+『of』+『a』(『an』)+『名』の形で》…のような・《『名』+『of』+『mine』(『yours, his』など独立所有格)の形で》…の…・《時》(1)《副詞句を作って》…に《形容詞句を作って》…の・《時刻》《米》…前(to,《米》before)
OLD French古[代]フランス語

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/09/15 16:33:07」(JST)

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The circle of Willis (also called Willis' circle, loop of Willis, cerebral arterial circle, and Willis polygon) is a circulatory anastomosis that supplies blood to the brain and surrounding structures. It is named after Thomas Willis (1621–1675), an English physician.^[1]

Structure

The circle of Willis is a part of the cerebral circulation and is composed of the following arteries:^[2]

Anterior cerebral artery (left and right)
Anterior communicating artery
Internal carotid artery (left and right)
Posterior cerebral artery (left and right)
Posterior communicating artery (left and right)
Basilar artery

The middle cerebral arteries, supplying the brain, are not considered part of the circle.

Origin of arteries

The left and right internal carotid arteries arise from the left and right common carotid arteries.

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

All arteries involved give off 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.

Variation

Considerable anatomic variation exists in the circle of Willis. Based on a study of 1413 brains, the classic anatomy of the circle is only seen in 34.5% of cases.^[3] In one common variation the proximal part of the posterior cerebral artery is narrow and its ipsilateral posterior communicating artery is large, so the internal carotid artery supplies the posterior cerebrum. In another variation the anterior communicating artery is a large vessel, such that a single internal carotid supplies both anterior cerebral arteries.

Function

The arrangement of the brain's arteries into the circle of Willis creates redundancies or collaterals 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.^[4]

Clinical significance

Aneurysms

Circle of Willis with the most common locations of ruptured aneurysms marked

Subclavian steal syndrome

The redundancies that the circle of Willis introduce can also lead to reduced cerebral perfusion.^[5]^[6] In subclavian steal syndrome, blood is "stolen" from the circle of Willis to preserve blood flow to the upper limb. Subclavian steal syndrome results from a proximal stenosis (narrowing) of the subclavian artery, an artery supplied by the aorta which is also the same blood vessel that eventually feeds the circle of Willis via the vertebral artery.

Additional images

Fetal ultrasound image at the level of circle of Willis, showing PCA, MCA and ACA
Cerebral angiogram showing an anterior/posterior projection of the vertebrobasilar and posterior cerebral circulation, the posterior aspect of the circle of Willis and one of its feeding vessels.
An anterior view of major cerebral and cerebellar arteries.
Circle of Willis
Circle of Willis

References

^ Uston, Cagatay (February 20, 2004). "Dr. Thomas Willis' Famous Eponym: The Circle of Willis" (PDF). Turkish Journal of Medical Sciences 34: 271–274. Retrieved 16 July 2010.
^ Purves, Dale; George J. Augustine; David Fitzpatrick; William C. Hall; Anthony-Samuel LaMantia; James O. McNamara; Leonard E. White (2008). Neuroscience, 4th Ed. Sinauer Associates. pp. 834–5. ISBN 978-0-87893-697-7.
^ 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.
^ Boorder, Michiel J.; Van Der Grond, J; Van Dongen, AJ; Klijn, CJ; Jaap Kappelle, L; Van Rijk, PP; Hendrikse, J (2006). "Spect measurements of regional cerebral perfusion and carbon dioxide reactivity: Correlation with cerebral collaterals in internal carotid artery occlusive disease". J Neurol 253 (10): 1285–1291. doi:10.1007/s00415-006-0192-1. PMID 17063318.
^ Klingelhöfer, J; Conrad, B; Benecke, R; Frank, B (1988). "Transcranial Doppler ultrasonography of carotid-basilar collateral circulation in subclavian steal". Stroke; a journal of cerebral circulation 19 (8): 1036–42. doi:10.1161/01.STR.19.8.1036. PMID 3041649.
^ Lord, RS; Adar, R; Stein, RL (1969). "Contribution of the circle of Willis to the subclavian steal syndrome". Circulation 40 (6): 871–8. doi:10.1161/01.CIR.40.6.871. PMID 5377222.

UpToDate Contents

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English Journal

The arterial circle of the brain, its branches and connections in selected representatives of the Antilopinae.

Frąckowiak H1, Dębiński D1, Komosa M1, Zdun M1.
Journal of morphology.J Morphol.2015 Jul;276(7):766-71. doi: 10.1002/jmor.20377. Epub 2015 Feb 18.
The arterial circle of the brain, that is, the circle of Willis, and its branches in ruminants have been chiefly described in farm animals and only in selected wild species. In view of the deficit of information about this vascular region in numerous other species of the Ruminantia, the arteries of
PMID 25694115

Utility of dynamic computed tomography angiography in the preoperative evaluation of skull base tumors.

Bi WL1, Brown PA2, Abolfotoh M1,3, Al-Mefty O1, Mukundan S Jr2, Dunn IF1.
Journal of neurosurgery.J Neurosurg.2015 Jul;123(1):1-8. doi: 10.3171/2014.10.JNS141055. Epub 2015 Apr 3.
OBJECT The anatomical complexity of skull base tumors mandates detailed preoperative planning for safe resection. In particular, the location of critical vascular and bony structures can influence the surgical approach. Traditional methods, such as MRI, MR angiography and/or venography (MRA/MRV), CT
PMID 25839925

Hemodynamics in the Circle of Willis with Internal Carotid Artery Stenosis under Cervical Rotatory Manipulation: A Finite Element Analysis.

Lin W1, Ma X2, Deng D2, Li Y1.
Medical science monitor : international medical journal of experimental and clinical research.Med Sci Monit.2015 Jun 23;21:1820-6. doi: 10.12659/MSM.892822.
BACKGROUND The circle of Willis (CoW) plays an important role in cerebral collateral circulation. The hemodynamics changes in the CoW have usually been associated with the internal carotid artery (ICA) stenosis, but whether rotatory manipulation will affect it remains unknown. MATERIAL AND METHODS I
PMID 26103051

Japanese Journal

RNF213 rare variants in Slovakian and Czech moyamoya disease patients

PLOS ONE 11(10), 2016-10-13
NAID 120005853279

Formation of the circle of Willis during human embryonic development

Congenital Anomalies 56(5), 233-236, 2016-09-01
NAID 120005850220

術後晩期に大出血を来した下咽頭食道重複癌症例

頭頸部外科 26(1), 133-138, 2016
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★リンクテーブル★

リンク元	「大脳動脈輪」
拡張検索	「occlusive disease in circle of Willis」
関連記事	「circle」

「大脳動脈輪」

Circle of Willis
	Schematic representation of the circle of Willis, arteries of the brain and brain stem. Blood flows up to the brain through the vertebral arteries and through the internal carotid arteries.
	The arteries of the base of the brain. Basilar artery labeled below center. The temporal pole of the cerebrum and the cerebellar hemisphere have been removed on the right side. Inferior aspect (viewed from below).
Details
Latin	Circulus arteriosus cerebri; Circulus Willisi
Identifiers
Gray's	p.574
MeSH	A07.231.114.228.351
TA	A12.2.07.080
FMA	50454
	Anatomical terminology

　　[★]

英: cerebralarterial circle
同: ウィリス動脈輪ウィリスの動脈輪ウィリス大脳動脈輪 Willis動脈輪 Willisの動脈輪 arterial circle of Willis circle of Willis, circulus arteriosus cerebri Willisi、ウイリス輪、

脳底部の動脈走行構造

Henry Gray (1825-1861). Anatomy of the Human Body. 1918.

「occlusive disease in circle of Willis」

　　[★] ウィリス動脈輪閉塞症

「circle」

　　[★]

環、サークル

関: annulus、ring

[Ustun-1] Uston, Cagatay (February 20, 2004). "Dr. Thomas Willis' Famous Eponym: The Circle of Willis" (PDF). Turkish Journal of Medical Sciences 34: 271–274. Retrieved 16 July 2010.

[Purves-2] Purves, Dale; George J. Augustine; David Fitzpatrick; William C. Hall; Anthony-Samuel LaMantia; James O. McNamara; Leonard E. White (2008). Neuroscience, 4th Ed. Sinauer Associates. pp. 834–5. ISBN 978-0-87893-697-7.

[3] 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.

[4] Boorder, Michiel J.; Van Der Grond, J; Van Dongen, AJ; Klijn, CJ; Jaap Kappelle, L; Van Rijk, PP; Hendrikse, J (2006). "Spect measurements of regional cerebral perfusion and carbon dioxide reactivity: Correlation with cerebral collaterals in internal carotid artery occlusive disease". J Neurol 253 (10): 1285–1291. doi:10.1007/s00415-006-0192-1. PMID 17063318.

[5] Klingelhöfer, J; Conrad, B; Benecke, R; Frank, B (1988). "Transcranial Doppler ultrasonography of carotid-basilar collateral circulation in subclavian steal". Stroke; a journal of cerebral circulation 19 (8): 1036–42. doi:10.1161/01.STR.19.8.1036. PMID 3041649.

[6] Lord, RS; Adar, R; Stein, RL (1969). "Contribution of the circle of Willis to the subclavian steal syndrome". Circulation 40 (6): 871–8. doi:10.1161/01.CIR.40.6.871. PMID 5377222.

匿名

検索

案内

案内

circle of Willis