Collateral circulation is circulation in an area of tissue or an organ with a number of different pathways for blood to reach it. This is often as a result of anastamoses - branches formed between adjacent blood vessels.
An example of the usefulness of collateral circulation is a systemic thrombo-embolism in cats. This is when a thrombus lodges above the external iliac artery(Common Iliac Artery), blocking the external and internal iliac arteries and effectively shutting off all blood supply to the hind leg. Even though the main vessels to the leg are blocked, enough blood can get to the tissues in the leg via the collateral circulation in order to keep them alive.
Another example (in Humans) is where a person suffers an acute Myocardial Infarction (Heart Attack), collateral circulation in the Heart tissue will sometimes by pass the blockage in the main artery and supply enough oxygenated blood to enable the Cardiac tissue to survive and recover.
Famous quotes containing the word circulation:
“There is probably not more than one hundred dollars in cash in circulation today. That is, if you were to call in all the bills and silver and gold in the country at noon tomorrow and pile them on the table, you would find that you had just about one hundred dollars, with perhaps several Canadian pennies and a few peppermint Life Savers.”
—Robert Benchley (1889–1945)