Willis' arterielle sirkel

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Willis' arterielle sirkel
Skjematisk fremstilling av Willis' arterielle sirkel, arterier til hjernen og hjernestammen.
Hjernen og arteriene på skallebasis. Tinninglapp-polen og en del av cerebellar-hemisfærene har blitt fjernet på høyre side. Sett nedenfra.
Latin	circulus arteriosus cerebri
Gray's	subject #147 574
MeSH	A07.231.114.228.351

Willis' arterielle sirkel (Latin: circulus arteriosus cerebri) er en sirkel av arterier som forsyner hjernen. Den er oppkalt etter Thomas Willis (1621-1673), en engelsk lege.^[1]

Innhold 1 Komponenter 2 Fysiologisk betydning 3 Anatomiske variasjoner 4 Subclavian steal og Willis' arterielle sirkel 5 Arterienes opprinnelse 6 Referanser 7 Eksterne lenker 8 Flere bilder

[rediger] Komponenter

• Arteria cerebri anterior (høyre og venstre)
• Arteria cerebri communicans anterior
• Arteria carotis interna (høyre og venstre)
• Arteria cerebri posterior (høyre og venstre)
• Arteria cerebri communicans posterior (høyre og venstre)

Arteria basilaris og arteria cerebri media, selv om de forsyner hjernen, betraktes ikke som deler av sirkelen.^[2]

[rediger] Fysiologisk betydning

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]

[rediger] Anatomiske variasjoner

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]

[rediger] Subclavian steal og Willis' arterielle sirkel

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.

[rediger] Arterienes opprinnelse

Høyre og venstre arteria carotis interna avgår fra høyre og venstre arteria carotis communis.

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 arteroa subclavia.

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 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.

[rediger] Referanser

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.

[rediger] Eksterne lenker

• Variations of Circle of Willis and Related Vessels - Illustrated Encyclopedia of Human Anatomic Variation
• Picture of the Circle of Willis (cadaver) - North Harris College

[rediger] Flere bilder

Gray's skjematiske fremstilling av Willis' arterielle sirkel.