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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]
These form the ventricular system of the brain: [8] The neural stem cells of the developing brain, principally radial glial cells, line the developing ventricular system in a transient zone called the ventricular zone. [9] The prosencephalon divides into the telencephalon, which forms the cortex of the developed brain, and the diencephalon.
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.
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]
In vertebrates, the circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the body. [1] [2] It includes the cardiovascular system, or vascular system, that consists of the heart and blood vessels (from Greek kardia meaning heart, and Latin vascula meaning vessels).
This blood vessel is called your aorta. An aortic aneurysm often doesn’t cause symptoms, but it can lead to severe, sudden bleeding from a ruptured aneurysm. A ruptured aneurysm has a high risk ...
A perivascular space, also known as a Virchow–Robin space, is a fluid-filled space surrounding certain blood vessels in several organs, including the brain, [1] potentially having an immunological function, but more broadly a dispersive role for neural and blood-derived messengers. [2] The brain pia mater is reflected from the surface of the ...