Changes

<br> <u>Note</u>: The basilar artery and middle cerebral arteries, though they supply the brain, are not considered part of the circle.  

<br> <u>Note</u>: The basilar artery and middle cerebral arteries, though they supply the brain, are not considered part of the circle.  

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=== Rete Mirable ===

==Rete Mirable==

[[Image:Carotidretesheep.jpg|thumb|right|150px|Carotid Rete of the Sheep. Sophie Stenner, RVC 2008]]  

[[Image:Carotidretesheep.jpg|thumb|right|150px|Carotid Rete of the Sheep. Sophie Stenner, RVC 2008]]  

The Rete Mirabile is a complex network of arteries and veins lying very close to each other and depends on a countercurrent blood flow between the arterioles and venuoles (blood flowing in opposite directions). It exchanges heat, ions, or gases between vessel walls so that the two bloodstreams within the rete maintain a gradient. The image shows the countercurrent exchange in the carotid rete mirable (carotid rete) of a sheep controlling the temperature of blood supplied to the brain.

The Rete Mirabile is a complex network of arteries and veins lying very close to each other and depends on a countercurrent blood flow between the arterioles and venuoles (blood flowing in opposite directions). It exchanges heat, ions, or gases between vessel walls so that the two bloodstreams within the rete maintain a gradient. The image shows the countercurrent exchange in the carotid rete mirable (carotid rete) of a sheep controlling the temperature of blood supplied to the brain.