Regulates blood flow by developing collateral circulation

2021-05-27 02:26 PM

The opening of the collateral circulation then over the next several hours, so that within 1-day half of the tissues requiring blood can be met, and within a few days blood flow is usually sufficient to reach the tissues.

In most tissues of the body, when an artery or vein is blocked, a new vascular channel usually grows around and allows partial re-supply of blood to the tissue to which the blocked blood vessel resides. The first step in this process is the dilation of the small blood vessels to make them ready to connect with the blood vessels above the blockage to the blood vessel below. While vasodilation occurs within the first minute or two, the flow is usually still less than a quarter of the amount required by all tissues. However, the opening of the collateral circulation follows over the next several hours, so that within 1-day half of the blood-requiring tissues can be met, and within a few days, blood flow is usually sufficient to reach the blood vessels. tissue.

The collateral circulation continues to develop for several months afterwards, often connecting many small vessels rather than a single large vessel. At rest, blood flow can also roughly meet the needs of the tissue, but these new vascular channels rarely grow larger to provide the blood flow needed during active activity. Thus, the development of accessory vessels follows the usual principles of both immediate and long-term control of local blood flow, the immediate control being rapid vasodilation, followed by growth and opening. widen new blood vessels over the course of a few weeks or months.

An important example of collateral development occurs after the embolization of one of the coronary arteries. From the age of 60 on, most people experience occlusion or at least partial occlusion of one or more of the small branches of the coronary arteries without knowing it because there are collateral circulations that grow rapidly enough to prevent myocardial damage. When the accessory blood vessels are not able to grow fast enough to maintain blood flow due to the rapidity or severity of coronary ischemia, a serious heart attack occurs.