The veins of the right axilla, viewed from in front.
Deep veins are almost always beside an artery with the same name (e.g. the femoral vein is beside the femoral artery). Collectively, they carry the vast majority of the blood. Occlusion of a deep vein can be life-threatening and is most often caused by thrombosis. Occlusion of a deep vein by thrombosis is called deep vein thrombosis.
Because of their location deep within the body, operation on these veins can be difficult.