Roots of brachial plexus

The roots of brachial plexus correspond to the anterior rami of spinal nerves C5, C6, C7, C8, and T1. These roots exit the vertebral canal through the intervertebral foramina and travel between the anterior and middle scalene muscles before entering the posterior triangle of the neck.

Several important nerves arise from the roots of brachial plexus:

• Branches to segmental neck muscles: These include the longus colii (C2-C6) as well as the anterior (C4-C7), middle (C3-C7), and posterior (C5-C7) scalene muscles.

• Dorsal scapular nerve: Originating from the C5 root, this nerve innervates the levator scapulae, rhomboid major, and rhomboid minor muscles. It often courses alongside the dorsal scapular artery.

• Long thoracic nerve: Derived from the C5, C6, and C7 roots, this nerve supplies the serratus anterior muscle as it travels with the lateral thoracic artery.

• Contribution to the phrenic nerve: A branch from the C5 root contributes to the formation of the phrenic nerve.

Within the floor of the posterior triangle, the roots of brachial plexus merge to form three trunks: the superior, middle, and inferior trunks.