Anterior Root of Eighth Cervical Nerve (Right)

Origin

The anterior root of the eighth cervical nerve forms from a series of rootlets that emerge from the anterolateral sulcus of the eighth cervical spinal segment.

Course

The anterior root of the eighth cervical nerve runs laterally and inferiorly away from the sixth cervical spinal segment towards the intervertebral foramen located between the seventh cervical and first thoracic vertebrae. Roughly within this intervertebral foramen, the anterior root merges with the posterior root to form the eighth cervical nerve.

Size and direction of the spinal roots vary. For instance, the upper cervical roots are short and run horizontally to exit the vertebral canal through the foramen.

Branches

The anterior root of the eighth cervical nerve merges with the posterior root to form the eighth cervical nerve and does so without branching.

Supplied Structures

The somatic motor efferents pass through the spinal nerve itself and into either the posterior ramus or the anterior ramus of the eighth cervical nerve.

Efferent fibers passing through the anterior ramus convey motor fibers to the inferior trunk of the brachial plexus. Fibers that enter the medial cord of the brachial plexus provide motor innervation to the pectoralis major and minor muscles, flexor digitorum profundus, palmaris brevis, palmar and dorsal interossei, third and fourth lumbricals, adductor pollicis, and hypothenar muscles. Fibers that enter the posterior cord provide motor innervation to the latissimus dorsi, triceps, anconeus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis.

Fibers that pass through the posterior ramus innervate the longissimus colli, splenius colli, iliocostalis colli, multifidus, semispinalis colli, semispinalis capitis, and trapezius.