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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 in reptiles, birds and mammals, including humans. [1] It is named after Thomas Willis (1621–1675), an English physician. [2]
In human anatomy, the left and right posterior communicating arteries are small [1]: 471 arteries at the base of the brain that form part of the circle of Willis. Anteriorly, it unites with the internal carotid artery (ICA) (prior to the terminal bifurcation of the ICA into the anterior cerebral artery and middle cerebral artery ); posteriorly ...
Collateral circulation is the alternate circulation around a blocked artery or vein via another path, such as nearby minor vessels. [1] It may occur via preexisting vascular redundancy (analogous to engineered redundancy), as in the circle of Willis in the brain, or it may occur via new branches formed between adjacent blood vessels (neovascularization), as in the eye after a retinal embolism ...
Circle of Willis (in the brain) Coronary: anterior interventricular artery and posterior interventricular artery of the heart; Scapular anastomosis (for the subclavian vessels) Joint anastomoses: Almost all joints receive anastomotic blood supply from more than one source. Shoulder (and circumflex humeral) Elbow (see blood supply of elbow)
The anterior choroidal artery typically originates from the internal carotid artery.It may (rarely) instead arise from the middle cerebral artery. [1]It originates from the distal internal carotid artery (ICA) 5 mm distal to the origin of the posterior communicating artery and just proximal to the terminal bifurcation of the ICA.
The basilar artery (U.K.: / ˈ b æ z. ɪ. l ə /; [1] [2] U.S.: / ˈ b æ s. ə. l ər / [3]) is one of the arteries that supplies the brain with oxygen-rich blood.. The two vertebral arteries and the basilar artery are known as the vertebral basilar system, which supplies blood to the posterior part of the circle of Willis and joins with blood supplied to the anterior part of the circle of ...
In case of narrowing of other arteries of the circle of Willis or the arteries supplying the circle, the anterior communicating artery can provide a way to supply blood to the opposite (affected) side of the circle. This can often preserve the cerebral blood supply well enough to avoid the symptoms of ischemia. [7]
The basilar artery is the main blood supply to the brainstem and connects to the Circle of Willis to potentially supply the rest of the brain if there is compromise to one of the carotids. At each cervical level, the vertebral artery sends branches to the surrounding musculature via the anterior spinal arteries.