The bypass circulation or collateral circulation is the path through which blood flows around a blocked arterial or venous valve (depending on which of the two types of vessels the path goes through). When an artery or vein is blocked, blood flow stops, so blood flow is redirected to neighboring vessels to maintain circulation. This in turn is called collateral circulation.
Stagnation of blood in the body can lead to serious consequences due to lack of oxygen and nutrients. The causes and mechanisms of development of collateral circulation will be discussed in this article.
It is very important to note that the circulatory system is one of the actively changing systems of the body. Its main task is to ensure blood circulation in the tissues and organs of the body and saturate them with oxygen and nutrients. Collateral blood flow is the preservation and maintenance of blood circulation when the main blood flow paths are blocked. Lack of tissue nutrition leads to the impossibility of full functioning of tissues and organs, causing the development of ischemia, which is easier to prevent than to cure. Because the networks of blood vessels throughout the body are intricate, even a one-sided blockage of a vein or artery causes severe redistribution of blood circulation. When transient closure of one of the major vessels occurs, the blood supply to the distal part of the body is significantly reduced, and perfusion below the occluded vessel may be significantly reduced. On the other hand, after passing through the main circulation, the collateral response involves many small vascular branches, capillaries and small arterioles in the tissues around the main vessel, which somehow function to supply blood to non-essential peripheral tissues of that area of the body. Consequently, collateralization gives more flexibility to the general circulatory system and determines the maximum peripheral anatomical length of arteries and veins.