The Circle of Willis is a circulatory anastomosis that supplies blood to the brain and surrounding structures. It is a ring-like structure located at the base of the brain around the optic chiasm and the infundibulum of the pituitary stalk. It is named after Thomas Willis, a 17th-century English physician.
The Circle of Willis is formed by the joining of several major arteries at the base of the brain. These arteries include:
1. Anterior cerebral arteries (ACA): These arteries arise from the internal carotid arteries and supply blood to the frontal lobes and medial portions of the brain.
2. Posterior cerebral arteries (PCA): These arteries also arise from the internal carotid arteries and supply blood to the occipital lobes and inferior portions of the brain.
3. Internal carotid arteries: These are the main arteries that supply blood to the brain. They branch into the anterior cerebral and middle cerebral arteries.
4. Posterior communicating arteries: These arteries connect the internal carotid arteries to the posterior cerebral arteries and help complete the circle.
5. Anterior communicating artery: This artery connects the two anterior cerebral arteries and helps complete the circle.
The Circle of Willis plays an important role in providing collateral circulation to the brain. If there is a blockage or stenosis in one of the arteries supplying the brain, the Circle of Willis can help maintain blood flow to the affected areas by redistributing blood through the other arteries.
It is important for medical professionals to understand the anatomy of the Circle of Willis as variations in its structure can impact the risk of certain neurological conditions such as strokes.
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