Posterior cord of brachial plexus is formed by

Cords of brachial plexus are formed by : (i) The lateral cord - It is formed by the union of the ventral divisions of the upper and middle trunks. (ii) The medial cord - It is formed by the ventral division of the lower trunk. (iii) The posterior cord -It is formed by union of the dorsal divisions of all the three trunks. Ref : B D Chaurasia's Human Anatomy , seventh edition , volume 1 , pg. no., 57.