Lateral Cord of Brachial Plexus

Origin

The origin of the lateral cord is from the anterior divisions of both the superior trunk and middle trunk. It carries fibers from the C5, C6, and C7 spinal segments.

Course

From its origin roughly lateral to the first rib, the lateral cord runs inferolaterally through the axilla. It is originally posterior to the first segment of the axillary artery, but by the second segment, it has assumed a position lateral to the axillary artery.

The lateral cord gives off one branch adjacent to the second segment of the axillary artery, the lateral pectoral nerve. It then continues down along the axillary artery until it terminates in the lower axilla, lateral to the third segment of the axillary artery.

The cords of the brachial plexus run within the axillary sheath which is an inferior extension of the prevertebral fascia.

Branches

The lateral cord gives rise to the following nerves:

—lateral pectoral nerve;

—musculocutaneous nerve;

—lateral half of the median nerve.

Supplied Structures

The lateral cord conveys both sensory and motor innervation. For sensory, it innervates anterior and lateral surfaces of the forearm, hand, and fingers. Motor innervation includes the muscles of the hand and anterior compartments of the arm and forearm. Broken down by nerve, the structures supplied by the lateral cord are:

—lateral pectoral nerve supplies motor innervation of the pectoralis major muscles and, through the ansa pectoralis, a minor contribution to the pectoralis minor muscle;

—musculocutaneous nerve supplies sensory to skin of the lateral forearm and motor innervation to the muscles of the anterior compartment of the arm;

—median nerve supplies sensory to skin of the lateral palmar surface of the hand and finger tips and all intrinsic muscles of the hand and forearm flexors not innervated by the ulnar nerve.