Lateral pectoral nerve
The lateral pectoral nerve, also called the lateral anterior thoracic nerve, is a branch of the lateral cord of the brachial plexus. Occasionally, it may also arise from the anterior divisions of the upper and middle trunks of the brachial plexus. The lateral pectoral nerve carries fibers from C5, C6 and C7 spinal nerves. After emerging, the nerve runs anteriorly, piercing the clavipectoral fascia to reach the deep surface of pectoral muscles.
The lateral pectoral nerve mostly carries motor fibers. Its main function is to provide motor innervation primarily to the pectoralis major muscle, but also provides minor contributions to the pectoralis minor muscle.
This article will discuss the anatomy and function of the lateral pectoral nerve.
|Origin||Lateral cord of brachial plexus (C5, C6, C7)|
|Supply||Pectoralis major muscle, pectoralis minor muscle|
Origin, course and innervation
The lateral pectoral nerve (C5, C6, C7) typically arises as the most proximal branch of the lateral cord of the brachial plexus, immediately above or deep to the clavicle. From its origin, the nerve runs anteriorly across the axillary artery and vein towards the pectoral muscles. Together with the thoracoacromial artery, the lateral pectoral nerve pierces the costocoracoid membrane, which is the upper denser portion of the clavipectoral fascia that extends from the first rib to the coracoid process of the scapula. The nerve then terminates at the deep surface of the pectoralis major muscle, supplying it.
Shortly after emerging from the lateral cord, the lateral pectoral nerve sends a communicating branch to the medial pectoral nerve. This communicating branch forms a loop known as ansa pectoralis, which runs anterior to the first part of the axillary vessels, contributing nerve fibers that supply the pectoralis minor muscle.
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The medial pectoral nerve gives rise to muscular branches that mainly supply the pectoralis major muscle. This muscle is involved in adduction, internal rotation, flexion and extension of the arm at the shoulder joint, as well as drawing of the scapula anteroinferiorly at the scapulothoracic joint. Additionally, the lateral pectoral nerve sends a communicating branch to the medial pectoral nerve to innervate the pectoralis minor muscle. The lateral pectoral nerve also innervates the anterosuperior part of the glenohumeral joint capsule.
Learn more about the lateral pectoral nerve and other branches of the brachial plexus with the study unit below! After that, test yourself with our fully customizable quiz!
Lateral pectoral nerve injury
Injuries of the brachial plexus often result in the dysfunction of the lateral pectoral nerve. However, isolated lesions of the nerve are unusual and rare. The few reported cases of such lesions have been associated with traction injuries from sports, seat belts in car accidents and compression injury from repeated contractions of the pectoralis major muscle in targeted training regimens. The nerve can also be injured iatrogenically, during surgical procedures in the pectoral region such as breast surgery. Clinically, patients present with weakness and atrophy of the pectoral muscles or parts of these muscles. Treatment is either conservative or surgical, based on the severity of functional deficits.
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