Human Anatomy: Part 2 - K. A. Dyubenko, A. K. Kolomiytsev, Yu. B. Chaykovsky 2008

Special Part
Peripheral Nervous System, systema nervosum periphericum — General Overview
Spinal Nerves — Cervical Plexus

The Cervical plexus is formed by the anterior rami of the upper four cervical nerves (C_I-C_IV) (Fig. 187), which interconnect via loop-like anastomoses. The plexus is located lateral to the transverse processes of the vertebrae, anterior to the vertebral Muscles, and posterior to the prevertebral muscles. The Branches of the plexus are divided into sensory, motor, and mixed.

The sensory branches emerge from beneath the posterior border of the sternocleidomastoid Muscle slightly above its midpoint and fan out upwards, forwards, and downwards (Figs. 188, 189):

1. Lesser occipital nerve, n. occipitalis minor (C_I-C_II), courses towards the mastoid process and the lateral part of the occipital region.

2. Great auricular nerve, n. auricularis magnus (C_III-C_IV), runs along the sternocleidomastoid muscle superiorly, dividing into anterior and posterior branches (rami anterior et posterior). The former innervates the Skin in the region of the Cytology/practical/97.html">Parotid salivary gland, while the latter supplies the skin of the auricle and external acoustic meatus.

3. Transverse cervical nerve, n. transversus colli (С_II-С_III), courses anteriorly; near the anterior border of the sternocleidomastoid muscle, it divides into superior and inferior branches (rami superiores et inferiores), which innervate the skin of the anterior neck.

4. Supraclavicular nerves, nn. supraclaviculares (C_III-C_IV), divide into medial, intermediate, and lateral branches, which supply the skin of the upper anterior chest wall down to the level of the third rib, the clavicular region, and the posteroinferior part of the neck, respectively.

Motor branches:

1. Inferior ROOT of the cervical loop (radix inferior ansae cervicalis) is formed by fibers from the second and third cervical nerves and runs forward to join the superior root originating from the hypoglossal nerve trunk. This junction forms the cervical loop (ansa cervicalis), which gives rise to branches supplying the omohyoid, sternohyoid, and sternothyroid muscles.

2. Short branches supplying the anterior rectus capitis, lateral rectus capitis, longus capitis, longus colli, levator scapulae, anterior intertransversarii, sternocleidomastoid, and trapezius muscles.

Class="center">

Fig. 187. Cervical plexus, plexus cervicalis (sources of formation and its nerves)

Fig. 188. Cervical plexus, plexus cervicalis

Fig. 189. Areas of distribution of cutaneous NERVES OF THE HEAD and Neck (diagram)

The most important nerve of the cervical plexus is the mixed branch known as the phrenic nerve, nervus phrenicus (C_III-C_IV, occasionally C_V). It descends along The surface of the anterior scalene muscle, crosses the Subclavian Artery anteriorly, and enters the thoracic cavity through the superior thoracic aperture. Together with the pericardiophrenic artery, the phrenic nerve runs beneath the Pleura towards the root of the lung. Along its path, the right nerve first lies on the lateral surface of the SUPERIOR VENA CAVA, then courses 0.5 cm anterior to the root of the right lung, and finally passes along the lateral surface of the INFERIOR VENA CAVA to reach the Diaphragm slightly anterior and lateral to the caval opening (foramen v. cavae). The left nerve crosses the aortic arch anteriorly, passes 0.3 cm anterior to the root of the left lung, and reaches the diaphragm near its tendinous center. In addition to muscular branches to the diaphragm, the phrenic nerve gives off a pericardial branch (ramus pericardiacus) to the Pericardium and pleura, as well as phrenicoabdominal branches (rami phrenicoabdominales) to the diaphragmatic Peritoneum. These branches anastomose with the celiac plexus (plexus coeliacus), which is particularly well-developed on the right side. This accounts for the referral of pain to the neck region (phrenic nerve sign) in Liver diseases.

NERVES OF THE CERVICAL PLEXUS

Summary Table