The cervical plexus is a network of nerves that form from the anterior rami of C1-C4 within the prevertebral fascia in the posterior triangle of the neck. Found bilaterally, its branches can loosely be divided into sensory and motor components.
The main sensory branches of the cervical plexus include the following:
The main motor branches of the cervical plexus primarily innervate the muscles of the neck and upper back. The most prominent of these is the ansa cervicalis, which is a loop formed by contributions from C1-C3 that gives off branches to most of the infrahyoid muscles.
The phrenic nerve is an important branch of the cervical plexus. It is formed at the posterior border of the anterior scalene muscle by fibres from C3, 4, and 5 nerve roots. After forming, the left and right phrenic nerves travel down through the mediastinum, passing anteriorly to their respective lung roots before terminating in the diaphragm. They provide motor innervation to the ipsilateral hemidiaphragm and relay sensory information from the mediastinal pleura, the pericardium, the central part of the diaphragm, and the surrounding pleura and peritoneum.
In summary, the cervical plexus is a network of nerves that form from the anterior rami of C1-C4 within the prevertebral fascia in the posterior triangle of the neck. It contains both sensory and motor branches with the phrenic nerve being an important branch of the plexus. The sensory branches of the plexus provide sensation to various parts of the neck and upper sternum, while the motor branches provide innervation to the muscles of the neck and upper back.
