Medial pectoral nerve

A nerve of the brachial plexus that innervates the pectoral muscles

Medial Pectoral Nerve

The medial pectoral nerve is a significant component of the brachial plexus, which is a network of nerves that originates from the spinal cord in the neck and supplies the upper limb. This nerve plays a crucial role in the innervation of the pectoralis major and pectoralis minor muscles, which are important for movements of the shoulder and arm.

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Diagram of the brachial plexus, showing the medial pectoral nerve.

Anatomy

The medial pectoral nerve arises from the medial cord of the brachial plexus, which is formed by the anterior divisions of the lower trunk. It typically receives contributions from the C8 and T1 nerve roots. The nerve travels inferiorly and laterally, passing behind the first part of the axillary artery.

Course

The medial pectoral nerve pierces the pectoralis minor muscle and continues to supply the pectoralis major muscle. It often communicates with the lateral pectoral nerve, forming a loop known as the "ansa pectoralis." This communication allows for coordinated innervation of the pectoral muscles.

Innervation

• Pectoralis Minor: The medial pectoral nerve provides motor innervation to the pectoralis minor, a thin, triangular muscle located beneath the pectoralis major. This muscle assists in stabilizing the scapula by drawing it anteriorly and inferiorly against the thoracic wall.
• Pectoralis Major: The nerve also innervates the lower part of the pectoralis major, a large, fan-shaped muscle that covers the upper part of the chest. This muscle is responsible for movements such as adduction and medial rotation of the humerus.

Function

The primary function of the medial pectoral nerve is to facilitate the movement of the shoulder joint by controlling the pectoral muscles. These muscles are involved in various actions, including:

• Adduction of the arm
• Medial rotation of the arm
• Flexion of the arm at the shoulder joint

Clinical Significance

Injury to the medial pectoral nerve can result in weakness or paralysis of the pectoral muscles, leading to difficulties in performing actions such as pushing or lifting. Such injuries may occur due to trauma, surgical procedures, or compression by surrounding structures.

Surgical Considerations

During surgical procedures involving the axilla or breast, care must be taken to avoid damaging the medial pectoral nerve. Surgeons often identify and preserve this nerve to maintain the function of the pectoral muscles.

Related Pages

• Brachial plexus
• Pectoralis major
• Pectoralis minor
• Lateral pectoral nerve