The anterior divisions of the upper and middle trunks of the brachial plexus unite to form a cord, which is situated on the lateral side of the second part of the axillary artery, and is called the lateral cord or fasciculus of the plexus.
Musculocutaneous: 5, 6, 7 C
Lateral anterior thoracic: 5, 6, 7 C
Lateral head of median: 6, 7 C
The anterior division of the lower trunk passes down on the medial side of the axillary artery, and forms the medial cord or fasciculus of the brachial plexus.
Medial anterior thoracic: 8 C, 1 T
Medial antibrachial cutaneous: 8 C, 1 T
Medial brachial cutaneous: 8 C, 1 T
Ulnar: 8 C, 1 T
Medial head of median: 8 C, 1 T
The posterior divisions of all three trunks unite to form the posterior cord or fasciculus of the plexus, which is situated behind the second portion of the axillary artery.