Arterial bypass. Artwork of a bypass around a narrowed region of the right femoral artery (red, down centre) of the human thigh. The bypass consists of a section of the saphenous vein (blue, tied off) that was grafted onto the artery. Muscles (orange) are also seen. The lining of the artery, seen in section, has been narrowed by fatty plaques of atheroma (yellow, down centre), a condition known as atherosclerosis. Without treatment, the lowered blood supply may have caused tissue death.