Medial pectoral nerve

Origin and course

The medial pectoral nerve (C8, T1) arises as the lateral branch of the medial cord of the brachial plexus. It originates posterior to the axillary artery. Upon originating, the nerve runs anteriorly towards the pectoral muscles alongside the axillary vein and axillary artery. Before reaching the inferior margin of the pectoralis minor muscle, the nerve receives a communicating branch from the lateral pectoral nerve making a nerve loop known as ansa pectoralis.

The nerve partially terminates by penetrating the pectoralis minor muscle. Some fibers emerge from the lateral aspect of the muscle and continue towards the pectoralis major muscle to supply it.

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Branches and innervation

As mentioned previously, the medial pectoral nerve gives off two sets of muscular branches; one for supplying the pectoralis minor, and the other for supplying a portion of the pectoralis major.

This specific part of the pectoralis major functions to extend the arm at the shoulder from a flexed position. Therefore, the injury of this nerve commonly leads to the inability to elevate the shoulder.