The subclavian vein is the continuation of the axillary vein and is so-named because it lies wholly behind the clavicle. The subclavian vein begins at the outer boundary of the first rib, runs medially and slightly upward, and ends at the medial border of the scalenus anterior by joining the internal jugular vein to form the innominate vein. It corresponds therefore to the third and second parts of the subclavian artery.
The subclavian vein lies on the first rib in front of the scalenus anterior – which separates it from the second part of the artery. It is therefore in front of the artery; but, owing to the slope of the rib, it is at a lower level. Anterior to it, there are the clavicle, the nerve to the subclavius, and the subclavius muscle itself.
The subclavian vein has only one tributary, and that is the external jugular vein, which joins it at the lateral margin of the scalenus anterior. It has one valve – placed on the distal side of the entrance of the external jugular.