Anterior Ramus of Fifth Cervical Nerve

Origin

The anterior ramus of the fifth cervical nerve originates from the fifth cervical nerve.

Course

The anterior ramus of the fifth cervical nerve originates in the neck, lateral to the intervertebral foramen between the fourth and fifth cervical vertebrae. It runs laterally towards the space between the anterior and middle scalene muscles where it joins the anterior ramus of the sixth cervical nerve to form the superior trunk of the brachial plexus.

Branches

Some fibers from the anterior ramus of the fifth cervical nerve, along with fibers from the anterior rami of the third and fourth cervical nerves, contribute to the phrenic nerve. The remaining bulk of the anterior ramus of the fifth cervical nerve joins with the anterior ramus of the sixth cervical nerve to form the superior trunk of the brachial plexus. Th phrenic nerve is not classified as a nerve of the brachial plexus.

While the bulk of the fifth anterior ramus becomes the superior root of superior trunk of the brachial plexus, it gives rise to the following nerves also (with contributions from other roots in parentheses):

—dorsal scapular nerve;

—subclavian nerve (C6);

—long thoracic nerve (C6, C7).

Supplied Structures

The anterior ramus of the fifth cervical nerve carries both sensory and motor innervation. Broken down by nerve, the following structures are supplied directly by the fifth anterior ramus.

—Dorsal scapular nerve supplies motor innervation of the levator scapulae, rhomboid minor, and rhomboid major muscles;

—Subclavian nerve supplies motor innervation of the subclavius muscle;

—Long thoracic nerve supplies motor innervation of the serratus anterior muscle.

The anterior ramus of the fifth cervical nerve carries fibers to all nerves associated with the superior trunk of the brachial plexus, except for the thoracodorsal nerve. Broken down by nerve, the following structures are innervated by the fifth cervical ramus via the superior trunk.

—Lateral pectoral nerve supplies motor innervation of the pectoralis major muscles and, through the ansa pectoralis, a minor contribution to the pectoralis minor muscle.

—Musculocutaneous nerve supplies sensory to skin of the lateral forearm and motor innervation to the muscles of the anterior compartment of the arm.

—Median nerve supplies sensory to skin of the lateral palmar surface of the hand and finger tips and all intrinsic muscles of the hand and forearm flexors not innervated by the ulnar nerve.

—Upper subscapular nerve supplies motor innervation of the subscapularis muscle.

—Lower subscapular nerve supplies motor innervation of the subscapularis muscle.

—Axillary nerve supplies sensory to skin of the lateral arm and motor innervation of the deltoid and teres minor muscles.

—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.

The phrenic nerve contains both visceral sensory fibers from the pleura and motor fibers to the diaphragm.