Second Intercostal Nerve

Origin

The anterior ramus of second thoracic nerve (or second intercostal nerve) is one of two branches of the second thoracic nerve, the other being the posterior ramus.

Course

The anterior ramus passes forward, lying between the pleura of the lungs and the internal intercostal membranes. It then enters the space between the internal intercostal and innermost intercostal muscles to course through the second intercostal space. It is also accompanied by an intercostal artery and vein, where the vein sits closest to the rib above, followed by the artery and nerve. At the anterior portion of the intercostal space, the anterior ramus passes anterior to the transversus thoracis muscle and the internal thoracic vessels, where it reaches its termination as the anterior cutaneous branch.

Branches

Near its origin, the anterior ramus of the second thoracic nerve gives off a collateral branch that descends in the intercostal space and courses along the inferior border of the space, in the same plane as the anterior ramus itself.

The lateral cutaneous branch of the anterior ramus of second thoracic nerve is the intercostobrachial nerve. This nerve crosses the axilla to join the medial brachial cutaneous nerve in the medial arm.

The anterior cutaneous branch arises as the anterior ramus of second thoracic nerve reaches the anterior portion of the intercostal space. The anterior cutaneous branch also pierces the chest wall.

Supplied Structures & Function

The anterior ramus of second thoracic nerve supplies motor innervation to the intercostal muscles of the second intercostal space (external intercostal, internal intercostal, innermost intercostal), and transversus thoracis muscle, and sensory innervation to the skin overlying the second intercostal space.

The intercostobrachial nerve conveys sensory innervation from the skin of the medial and posterior arm and axilla.

List of Clinical Correlates

—Referred pain