Supraclavicular part of brachial plexus

The supraclavicular part of brachial plexus comprises structures above the clavicle, i.e., within the posterior triangle of the neck. These include the roots, trunks, and divisions of the plexus.

Roots

The roots of the brachial plexus are the anterior rami of spinal nerves C5 to T1. These roots emerge through the intervertebral foramina and traverse the gap between the anterior and middle scalene muscles to enter the posterior triangle.

The branches given off from the roots include:

• Nerve branches to the segmental muscles of the neck, including the longus colii (C2-C6), and the anterior (C4-C7), middle (C3-C7), and posterior (C5-C7) scalene muscles.

• Phrenic nerve (C3, C4, C5): Innervates the diaphragm.

• Dorsal scapular nerve (C5): Innervates the levator scapulae, rhomboid major, and rhomboid minor muscles.

• Long thoracic nerve (C5-C7): Innervates the serratus anterior muscle.

Trunks

Within the floor of the posterior triangle, the roots combine to form three trunks:

• Superior trunk: Formed by the union of the C5 and C6 roots.

• Middle trunk: A continuation of the C7 root.

• Inferior trunk: Formed by the union of the C8 and T1 roots

Two branches arise from the trunks:

• Suprascapular nerve (C5, C6): Originates from the superior trunk and innervates the supraspinatus and infraspinatus muscles.

• Nerve to the subclavius (C5, C6): Arises from the superior trunk and innervates the subclavius muscle.

Divisions

Each trunk splits into an anterior division and a posterior division, occurring posterior to the clavicle. These divisions contribute to the formation of the cords of the brachial plexus (located in the infraclavicular region). Importantly, the divisions do not give rise to any branches.