Cords

The 3 cords of the brachial plexus are named according to their position relative to the axillary a.: lateral, medial, and posterior.  The cords are formed from the 6 divisions (3 anterior and 3 posterior) of the brachial plexus.  All three posterior divisions form the posterior cord.  Two of the anterior divisions form the lateral cord, and the remaining anterior division is the medial cord.  The cords then give rise to the 5 main branches of the the brachial plexus.