Occlusion of the artery ischemia occurs not only in cases where it is impossible for the blood of the arrival of other ways. But too often there is the possibility that the blood out another way to areas blocked artery, and often enough, and this is known as collateral circulation in the arteries. It often happens that a clogged artery branches anastomose with other neighbors, then both carry oxygenated blood to the area which had been removed from circulation. This is known as anastomosis, or collateral line, tying the branches, and collateral circulation built this way.
Collateral circulation varies from case to case. Sometimes quite from scratch and others (initially) solid. Let's first collateral circulation and there are usually between the radial and ulnar arteries, through the palmar arch. If the radial artery is blocked, the blood comes to the palm of the ulnar-at first, so that the blood reaches approximately half of the previous. But soon the blood flow through the ulnar faster than normal, so the hand will reach more of the same.
The opposite occurs when a narrow anastomosis that, despite the acceleration of blood flow and dilation of vessels immediately, it is not a sufficient amount of blood. This raises the disorder, may still be compensated. Collateral vessel dilation, which at first is that according to the normal capacity of adaptation, after exceeding the limit. Each element is multiplied walls, and glass, narrow at first, a big glass. Not only that there is a narrow artery anastomosis can experience this kind of growth, but under special conditions capillary tube could also be widened arteries and form on his wall all the characteristic elements of the arterial wall, thus avoiding tissue necrosis.
Collateral circulation can, therefore, even in a difficult pose but its development is much more difficult when there is a narrow collateral. However, sometimes the network does not support long prolonged blood deficit. Such as occurs, for example, when the femoral artery is clogged or garter above the starting point of the profunda femoris. Then established collateral circulation through the arterial anastomosis between the hip and femoral arterial muscle, so it is often too slow, then become necrotic foot and part of leg.
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