Medial pectoral nerve

The medial pectoral nerve, also known as the medial anterior thoracic nerve arises from the medial cord of the brachial plexus and supplies both the pectoralis minor and major muscles. 

Gross anatomy

Origin

The medial pectoral nerve arises from the medial cord of the brachial plexus with fibers arising from the eighth cervical and first thoracic nerve roots. 

Course

The medial pectoral nerve arises posterior to the axillary artery. It curves anteriorly to lie between the axillary artery and vein then, after receiving a communicating branch from the lateral pectoral nerve (the ansa pectoralis) enters the deep surface of the pectoralis minor muscle. The medial pectoral nerve perforates the pectoralis minor muscle and enters the deep surface of pectoralis major supplying the lower sternocostal fibers of the muscle.  

Branches and supply

The medial pectoral nerve supplies both the pectoralis minor muscle and sternocostal portions of the pectoralis major muscle.

Relations

The medial pectoral nerve lies posterior to the axillary artery and anterior to the axillary vein. Along its course it receives a communicating branch from the lateral pectoral nerve to form a loop (ansa pectoralis) which runs anteriorly to both the axillary artery and vein.

Variant anatomy

The medial pectoral nerve may arise directly from the anterior division of the inferior trunk of the brachial plexus.