Collaterals

side branches or peripheral paths of blood flow supplying and draining blood while bypassing the principal blood-carrying trunk.

Collaterals supply blood to organs in cases of thrombosis or embolisms and compression or ligation of blood vessels. Intra-systemic collaterals are anastomoses between branches of the same artery or vein; intersystemic collaterals run along anastomoses of different arteries or veins.