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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]
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.
The pons in humans measures about 2.5 centimetres (0.98 in) in length. [2] It is the part of the brainstem situated between the midbrain and the medulla oblongata.
Changes in brain activity are closely coupled with changes in blood flow in those areas, and knowing this has proved useful in mapping brain functions in humans. The measurement of haemodynamic response, in a clinical setting, can be used to create images of the brain in which especially active and inactive regions are shown as distinct from ...
This continuous flow into the venous system dilutes the concentration of larger, lipid-insoluble molecules penetrating the brain and CSF. [9] CSF is normally free of red blood cells and at most contains fewer than 5 white blood cells per mm 3 (if the white cell count is higher than this it constitutes pleocytosis and can indicate inflammation ...
These maps incorporate individual neural connections in the brain and are often presented as wiring diagrams. [ 4 ] Brain mapping techniques are constantly evolving, and rely on the development and refinement of image acquisition, representation, analysis, visualization and interpretation techniques. [ 5 ]
The leptomeningeal collateral circulation (also known as leptomeningeal anastomoses or pial collaterals) is a network of small blood vessels in the brain that connects branches of the middle, anterior and posterior cerebral arteries (MCA, ACA, and PCA), [1] with variation in its precise anatomy between individuals. [2]
Cerebral perfusion pressure, or CPP, is the net pressure gradient causing cerebral blood flow to the brain (brain perfusion).It must be maintained within narrow limits because too little pressure could cause brain tissue to become ischemic (having inadequate blood flow), and too much could raise intracranial pressure (ICP).