Trunk of branch of subclavian artery, each instance of which is an artery that arises from the posterior aspect of some subclavian artery, arches backward, and at the neck of some first rib bifurcates into the trunks of some deep cervical and highest intercostal arteries, thus supplying blood to the structures contained in some first two intercostal spaces, the vertebral column, the muscles of some back, and some deep neck muscles.