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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]
Cerebral blood flow (CBF) is the blood supply to the brain in a given period of time. [8] In an adult, CBF is typically 750 millilitres per minute or 15.8 ± 5.7% of the cardiac output. [9] This equates to an average perfusion of 50 to 54 millilitres of blood per 100 grams of brain tissue per minute. [10] [11] [12]
It arises from the basilar artery on each side at the level of the junction between the medulla oblongata and the pons in the brainstem. It has a variable course, passing backward to be distributed to the anterior part of the undersurface of the cerebellum, anastomosing with both the posterior inferior cerebellar (PICA) branch of the vertebral ...
A disrupted blood supply to posterior inferior cerebellar artery due to a thrombus or embolus can result in a stroke and lead to lateral medullary syndrome. Severe occlusion of this artery or to vertebral arteries could lead to Horner's Syndrome as well.
Leptomeningeal collateral vessels from the anterior cerebral artery and posterior cerebral artery appeared to allow for perfusion of some brain tissue to persist, partially compensating for the loss of the major vessel. [6] This compensatory effect is however usually inadequate to maintain a normal blood supply. [11]
The brain is supplied with blood by the internal carotid arteries and also by the posterior cerebral arteries; the posterior communicating arteries connects the two systems. This provides redundancies or collaterals in the cerebral circulation so that, if one system is blocked or narrowed, the other can take over.
The anterior cerebral artery supplies a part of the frontal lobe, specifically its medial surface and the upper border. It also supplies the front four–fifths of the corpus callosum, and provides blood to deep structures such as the anterior limb of the internal capsule, part of the caudate nucleus, and the anterior part of the globus ...
3D model of cerebral veins. In human anatomy, the cerebral veins are blood vessels in the cerebral circulation which drain blood from the cerebrum of the human brain.They are divisible into external (superficial cerebral veins) and internal (internal cerebral veins) groups according to the outer or inner parts of the hemispheres they drain into.