n :  either of two arteries that branch from the axillary artery or from one of its branches:  a  :  a small artery that usu. arises from the axillary artery below the clavicle and that supplies or sends branches to the two pectoralis muscles and the walls of the chest - called also supreme thoracic artery   b  :  an artery that often arises from the thoracoacromial artery or from the subscapular artery rather than the axillary artery and that supplies both pectoralis muscles and the serratus anterior and sends branches to the lymph nodes of the axilla and to the subscapularis muscle - called also lateral thoracic artery  - compare INTERNAL THORACIC ARTERY  .
 
 
 
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