Medial pectoral nerve

At a glance

English

Medial pectoral nerve

Latin (TA2)

Nervus pectoralis medialis

System

Nerve

Region

Upper limb

Side

Paired, left and right

About the medial pectoral nerve

The medial pectoral nerve arises from the medial cord of the brachial plexus in the axilla, behind pectoralis minor, and carries fibres from the eighth cervical and first thoracic nerves. It is named after the cord it comes from rather than its final position: once it passes forward it actually lies lateral to the lateral pectoral nerve.

From its origin it curves forwards between the axillary artery and axillary vein. In front of the artery it is joined by a communicating twig from the lateral pectoral nerve, forming a loop called the pectoral ansa. It then enters the deep surface of pectoralis minor, supplies it, and sends branches through or around the lower border of that muscle into pectoralis major, where they serve the lower sternocostal fibres.

Through these muscles the nerve helps to draw the arm across the chest and to rotate it medially, and it helps steady the scapula against the chest wall. The nerve matters in breast and axillary surgery. During removal of lymph nodes from the axilla, it is sought and preserved where it crosses near pectoralis minor; cutting it leads to wasting of the lower pectoralis major. It is also a candidate donor in nerve transfer operations for brachial plexus injury.

Course and supply

Arises from

Medial cord of the brachial plexus (C8, T1) behind pectoralis minor.

Ends in

Ends in pectoralis minor and, through branches piercing or passing around it, in the lower sternocostal part of pectoralis major.

Supplies

Motor to pectoralis minor and the lower part of pectoralis major, which adduct and medially rotate the arm and draw the scapula forwards and down.