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 extends between the anterior and lateral rectus muscles of the head, the remaining anterior branches - between the anterior and posterior intervertebral muscles, behind the vertebral artery.

Cervical plexus, its branches and innervated organs

Nerves (branches) of the cervical plexus	Segments of the spinal cord	Innervable organs
Muscular branches	CI-CIV	Fore and lateral muscles of the head; long muscles of the head and neck; muscle lifting the scapula; stair and anterior interdigitic muscles; Chest-clavicular-mastoid and trapezius muscles
Upper and lower roots of the neck loop	CI-CIII	Breast-sublingual, sterno-thyroid, scapula-hyoid and musculoskeletal muscles
Small occipital nerve	CII-CIII	Skin of the lateral part of the occipital region
Large occipital nerve	CIII	Skin of the auricle and external auditory canal
The transverse nerve of the neck	CIII	Skin of the anterior and lateral regions of the neck
Supraclavicular nerves	CII-CIV	The skin of the lateral region of the neck and the area of the clavicle, as well as the skin above the deltoid and large pectoral muscles
Diaphragmatic nerve	CIII-CIV (CV)	Diaphragm, pleura, pericardium, peritoneum covering the diaphragm, liver and gallbladder

The plexus is located on the side of the transverse processes, between the beginning of the anterior staircase and the long neck muscle (medially), the middle staircase muscle, the muscle that lifts the scapula, and the neck muscle of the neck laterally. Front and side plexus is covered with a sternocleidomastoid muscle.

The cervical plexus has connections with the sublingual nerve with the help of the anterior branches of the first and second cervical spinal nerves, with the additional nerve, with the brachial plexus (through the anterior branch of the fourth cervical spinal nerve), with the superior cervical node of the sympathetic trunk.

From the cervical plexus, the muscle branches that innervate the long muscles of the head and neck, the stair muscles, the lateral and anterior rectus muscles of the head, the muscle that lifts the scapula, and the trapezius and sternum-clavicular-mastoid muscles come out of the cervical plexus. The cervical plexus also gives the fibers that form the radix inferior of the cervical loop. The upper root (radix superior) of this loop is formed by the descending branch of the hyoid nerve. Fibers emerging from the cervical loop innervate the superficial muscles of the neck located below the hyoid bone.

The sensitive branches of the cervical plexus are the small occipital nerve, the large auric nerve, the transverse nerve of the neck and the supraclavicular nerves. These nerves move away from the plexus, around the posterior edge of the sternocleidomastoid muscle and come out from under it into the subcutaneous tissue. The longest nerve of the cervical plexus is the diaphragmatic nerve.

1. The small occipital nerve (n. Occipitalis minor) is formed mainly by the branches of the second and third cervical spinal nerves. It goes under the skin at the back edge of the sternocleidomastoid muscle, it goes up and back and innervates the skin behind the auricle and above it.
2. The large auricularis (n. Auricularis magnus) consists mainly of fibers of the third and to a lesser degree of the fourth cervical spinal nerves. The projection of the exit of this nerve on the neck occurs at the border between the upper and middle third of the posterior margin of the sternocleidomastoid muscle. The large auricle is divided into the anterior and posterior branches, which are directed upwards. The posterior branch goes vertically upward and innervates the skin of the posterior and lateral surfaces of the auricle, the skin of the ear lobe. Some fibers perforate the cartilage of the auricle and innervate the skin of the external auditory canal. The anterior branch of the large ear nerve goes obliquely forward and innervates the skin of the face in the region of the parotid salivary gland.
3. The transverse nerve of the neck (n. Transversus colli) consists of the fibers of the anterior branch of the third cervical spinal nerve. The nerve emerges from under the posterior edge of the sternocleidomastoid muscle, is directed forward, gives the upper and lower branches that penetrate the subcutaneous muscle of the neck and go to the skin of the anterior sections of the neck. The transverse nerve of the neck is anastomosed 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. Supraclavicular nerves (nn. Supraclaviculares) are formed predominantly by the branches of the fourth and partly fifth cervical spinal nerves. 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 front region of the breast (to level III of the rib). Accordingly, the medial, intermediate and lateral supraclavicular nerves are distinguished (nn. Supraclaviculares mediales, intermedii et laterales).
5. The diaphragmatic nerve (n. Phrenicus) is formed predominantly by the anterior branches of the third and fourth cervical spinal nerves, descending steeply down the front surface of the anterior staircase, passes into the thoracic cavity between the subclavian artery and the vein, medial to the inner thoracic artery. Next, the nerve goes next to the dome of the pleura, anterior to the root of the lung, under the mediastinal pleura. The right diaphragmatic nerve passes along the lateral surface of the superior vena cava, adjacent to the pericardium, is located anterior to the left diaphragmatic nerve. The left diaphragmatic nerve crosses the aortic arch in the front and penetrates the diaphragm at the border of the tendon center and the rib part of it. The motor fibers of the diaphragm nerves innervate the diaphragm, the sensitive fibers go to the pleura and pericardium (pericardial branch, r. Pericardiacus). A part of the branches of the diaphragmatic nerve - diaphragmatic-abdominal branches (r. Phrenicoabdominales) passes into the abdominal cavity and innervates the peritoneum that lines the diaphragm. The right diaphragmatic nerve passes in transit (without interruption) through the celiac plexus to the peritoneum covering the liver and gallbladder.

[1], [2], [3], [4], [5]