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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]
Medical condition Subarachnoid hemorrhage Other names Subarachnoid haemorrhage CT scan of the brain showing subarachnoid hemorrhage as a white area in the center (marked by the arrow) and stretching into the sulci to either side Pronunciation / ˌ s ʌ b ə ˈ r æ k n ɔɪ d ˈ h ɛ m ər ɪ dʒ / Specialty Neurosurgery, Neurology Symptoms Severe headache of rapid onset, vomiting, decreased ...
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 ...
Willis was a pioneer in research into the anatomy of the brain, nervous system and muscles. His most notable discovery was the "Circle of Willis", a circle of arteries on the base of the brain. Willis's anatomy of the brain and nerves, as described in his Cerebri anatome of 1664, is minute and elaborate.
The results yielded 52% of normal brains having a normal circle of Willis, while only 33% of brains with cerebral softening had a normal circle of Willis. There were also a higher number of string-like vessels in brains with cerebral softening (42%), than there were in normal brains (27%).
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]
There are many examples of normal arterio-arterial anastomoses in the body. Clinically important examples include: Circle of Willis (in the brain) Coronary: anterior interventricular artery and posterior interventricular artery of the heart; Scapular anastomosis (for the subclavian vessels)
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.