n :  the proximal part of the main artery of the arm that arises on the right side from the brachiocephalic artery and on the left side from the arch of the aorta, that extends from its point of origin to the outer border of the first rib where it becomes the axillary artery and passes through the axilla and into the arm to become the brachial artery, and that supplies or gives off branches supplying the brain, neck, anterior wall of the thorax, and shoulder .
 
 
 
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