Posterior Division of Inferior Trunk of Brachial Plexus (Right)

Origin

The origin of the posterior division of the inferior trunk is from the inferior trunk itself. This occurs when the trunk bifurcates into anterior and posterior divisions. It carries fibers from the C8 and T1 spinal segments.

Course

The posterior division of the inferior trunk forms on the border of the posterior triangle and the axilla, roughly posterior to the mid-clavicle. It runs inferolaterally, assuming a position posterior to the first segment of the axillary artery.

The divisions of the brachial plexus run within the prevertebral fascia or its inferior extension, the axillary sheath.

Branches

The posterior division of the superior trunk itself has no branches as it generally does not give rise to any nerves. However, it merges with the posterior divisions of the superior and middle trunks to form the posterior cord, and contributes to the following nerves:

—thoracodorsal nerve;

—radial nerve.

The posterior division of the inferior trunk merges to form the posterior cord, but it gives no contribution to the upper subscapular, lower subscapular, and axillary nerves.

Supplied Structures

The posterior division of the inferior trunk supplies some of the structures innervated by the posterior cord. This includes posterior and lateral surfaces of the arm forearm, and hand (sensory), the latissimus dorsi and the muscles of the posterior compartment of the arm and forearm (motor). Broken down by nerve, the structures supplied by the posterior division of the inferior trunk are:

—thoracodorsal nerve supplies motor innervation of the latissimus dorsi muscle;

—radial nerve supplies sensory to skin of the posterolateral arm, posterior forearm, and posterolateral hand and motor innervation to the muscles of the posterior compartment of the arm and forearm.