Anterior Root of Third Cervical Nerve (Left)

Origin

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

Course

The anterior root of the third cervical nerve runs laterally and inferiorly away from the third cervical spinal segment towards the intervertebral foramen located between the axis (C2 vertebra) above and the third cervical vertebra below. Roughly within this intervertebral foramen, the anterior root merges with the posterior root to form the third 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 third cervical nerve merges with the posterior root to form the third 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 third cervical nerve.

Those passing through the anterior ramus contribute to the cervical plexus. It innervates the infrahyoid muscles (sternohyoid, sternothyroid and inferior belly of omohyoid) via the ansa cervicalis. Other muscles innervated include the anterior prevertebral muscles, including the longus capitis and longus colli, and lateral prevertebral muscles, including the middle scalene muscle.

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