Cervical plexus

The cervical plexus (plexus cervicales) is formed by the anterior branches of the four upper cervical (CI-CIV) spinal nerves. The anterior branch (CII) emerges between the anterior and lateral rectus capitis muscles, the remaining anterior branches emerge between the anterior and posterior intervertebral muscles, behind the vertebral artery.

Cervical plexus, its branches and innervated organs

Nerves (branches) of the cervical plexus	Spinal cord segments	Innervated organs
Muscular branches	CI-CIV	Anterior and lateral capitis; long capitis and colli muscles; levator scapulae; scalene and anterior intertransverse muscles; sternocleidomastoid and trapezius muscles
Upper and lower roots of the cervical loop	CI-CIII	Sternohyoid, sternothyroid, omohyoid and thyrohyoid muscles
Lesser occipital nerve	CII-CIII	Skin of the lateral part of the occipital region
Greater occipital nerve	CIII	Skin of the auricle and external auditory canal
Transverse nerve of the neck	CIII	Skin of the anterior and lateral areas of the neck
Supraclavicular nerves	CII-CIV	The skin of the lateral neck and clavicle area, as well as the skin over the deltoid and pectoralis major muscles
Phrenic nerve	CIII-CIV (CV)	Diaphragm, pleura, pericardium, peritoneum covering the diaphragm, liver and gallbladder

The plexuses are located laterally to the transverse processes, between the origin of the anterior scalene muscle and the longus colli muscle (medially), the middle scalene muscle, the levator scapulae muscle, and the splenius colli muscle laterally. The plexus is covered anteriorly and laterally by the sternocleidomastoid muscle.

The cervical plexus has connections with the hypoglossal nerve via the anterior branches of the first and second cervical spinal nerves, with the accessory nerve, with the brachial plexus (via the anterior branch of the fourth cervical spinal nerve), and with the superior cervical ganglion of the sympathetic trunk.

The cervical plexus gives off muscle branches that innervate the long muscles of the head and neck, the scalene muscles, the lateral and anterior rectus capitis, the levator scapulae, and the trapezius and sternocleidomastoid muscles. The cervical plexus also gives off fibers that form the inferior rootlet (radix inferior) of the cervical loop. The superior rootlet (radix superior) of this loop is formed by the descending branch of the hypoglossal nerve. The fibers that extend from the cervical loop innervate the superficial muscles of the neck, located below the hyoid bone.

The sensory branches of the cervical plexus are the lesser occipital nerve, the greater auricular nerve, the transverse nerve of the neck, and the supraclavicular nerves. These nerves depart from the plexus, bend around the posterior edge of the sternocleidomastoid muscle, and exit from under it into the subcutaneous tissue. The longest nerve of the cervical plexus is the phrenic nerve.

1. The lesser occipital nerve (n. occipitalis minor) is formed mainly by branches of the second and third cervical spinal nerves. It emerges under the skin at the posterior edge of the sternocleidomastoid muscle, runs upward and backward, and innervates the skin behind and above the auricle.
2. The great auricular nerve (n. auricularis magnus) consists mainly of fibers of the third and, to a lesser extent, the fourth cervical spinal nerves. The projection of this nerve's exit onto the neck is located at the border between the upper and middle thirds of the posterior edge of the sternocleidomastoid muscle. The great auricular nerve is divided into anterior and posterior branches, which go upward. The posterior branch goes vertically upward and innervates the skin of the posterior and lateral surfaces of the auricle, the skin of the earlobe. Some of the fibers pierce the cartilage of the auricle and innervate the skin of the external auditory canal. The anterior branch of the great auricular nerve goes obliquely forward and innervates the skin of the face in the area of the parotid salivary gland.
3. The transverse nerve of the neck (n. transversus colli) consists of fibers of the anterior branch of the third cervical spinal nerve. The nerve emerges from under the posterior edge of the sternocleidomastoid muscle, goes forward, gives off upper and lower branches that penetrate the subcutaneous muscle of the neck and go to the skin of the anterior parts of the neck. The transverse nerve of the neck anastomoses with the cervical branch of the facial nerve, the fibers of which come to the neck to innervate the subcutaneous muscle of the neck.
4. The supraclavicular nerves (nn. supraclaviculares) are formed mainly by branches of the fourth and partly fifth cervical spinal nerves. The supraclavicular nerves appear on the surface of the subcutaneous muscle of the neck at the level of the middle of the posterior edge of the sternocleidomastoid muscle, go down, fan out and innervate the skin above the clavicle and in the upper anterior region of the chest (up to the level of the third rib). According to their location, there are medial, intermediate and lateral supraclavicular nerves (nn. supraclaviculares mediales, intermedii et laterales).
5. The phrenic nerve (n. phrenicus) is formed mainly by the anterior branches of the third and fourth cervical spinal nerves, descends vertically down the anterior surface of the anterior scalene muscle, passes into the thoracic cavity between the subclavian artery and vein, medial to the internal thoracic artery. Then the nerve goes next to the dome of the pleura, in front of the root of the lung, under the mediastinal pleura. The right phrenic nerve passes along the lateral surface of the superior vena cava, adjoins the pericardium, and is located in front of the left phrenic nerve. The left phrenic nerve crosses the aortic arch in front and penetrates the diaphragm at the border of the tendinous center and its costal part. The motor fibers of the phrenic nerves innervate the diaphragm, the sensory fibers go to the pleura and pericardium (pericardial branch, r. pericardiacus). Part of the branches of the phrenic nerve - the phrenic-abdominal branches (rr. phrenicoabdominales) pass into the abdominal cavity and innervate the peritoneum lining the diaphragm. The right phrenic nerve passes in transit (without interruption) through the celiac plexus to the peritoneum covering the liver and gallbladder.

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