On the left side of the body, the subclavian comes directly off the arch of aorta. On the right side of the body, the subclavian arises from the relatively short brachiocephalic artery (trunk) when it bifurcates into the subclavian and the right common carotid artery.
The usual branches of the subclavian on both sides of the body are the vertebral artery, the thyrocervical artery (trunk), and the costocervical artery (trunk). The subclavian becomes the axillary artery at the lateral border of the first rib.
Embryologically, the left subclavian simply arises from the left 7th intersegmental artery, while the right subclavian arises, proximal to distal:
1. aortic arch IV
2. right dorsal aorta (between the 4th and the 7th intersegmental arteries)
3. right 7th intersegmental artery