I am a student studying the cardiac system, and have a question about coronary bypass, and I hope it does not sound too dumb. Why is the saphenous vein used for the bypass? It seems to me that this (or any) vein is insufficient because it it designed differently from an artery (with the one way valves, for one thing). Why isn't another artery used for bypass surgery? How can a vein do the same work as an artery does? Thanks.