General characteristics of neck nerves
Human anatomy distinguishes 8 pairs of cervical spinal nerves, designated from C₁ to C₈. The anterior and posterior rami of these nerves serve as the basis for the formation of cutaneous, muscular, and mixed nerves of the neck. It is from these structures that the cervical plexus (plexus cervicalis) is formed, the branches of which are distributed to various areas of the head, neck, and thorax.
Sensory (cutaneous) branches
The sensory nerves of the cervical plexus are responsible for innervating the skin of the head, neck, and upper trunk. Most of them are formed at the level of segments C₂–C₄.
- Lesser occipital nerve (n. occipitalis minor, C₂–C₃) is responsible for the skin sensitivity posterior to the auricle, as well as the lateral occipital region.
- Greater auricular nerve (n. auricularis magnus, C₂–C₃) innervates the skin of the parotid region, the auricle itself, and the area of the angle of the mandible.
- Transverse cervical nerve (n. transversus colli, C₂–C₃) collects sensory information from the skin of the anterior surface of the neck.
- Supraclavicular nerves (nn. supraclaviculares). Formed from segments C₃–C₄ and divided into three groups. The medial branches innervate the skin over the sternum and the medial part of the clavicle; the intermediate branches supply the upper chest and the anterior surface of the shoulder; the lateral branches provide skin sensitivity over the acromion and the lateral surface of the shoulder.
Also participating in the innervation of the occipital region are the greater occipital nerve (n. occipitalis major, C₂, skin up to the vertex) and the third occipital nerve (n. occipitalis tertius, C₃, skin of the lower occipital region).
Motor (muscular) branches
The motor part of the cervical plexus ensures the function of numerous muscles of the neck and head.
Suboccipital nerve (n. suboccipitalis, C₁) innervates the deep suboccipital muscles: the rectus capitis posterior major and minor muscles (m. rectus capitis posterior major and minor), as well as the obliquus capitis superior and inferior muscles (m. obliquus capitis superior and inferior).
The muscular branches of the plexus (rr. musculares) are distributed as follows:
- Fibres from C₁–C₄ pass to the longus colli and longus capitis muscles (m. longus colli, m. longus capitis), the rectus capitis anterior and lateralis muscles (m. rectus capitis anterior and lateralis), and the anterior, middle and posterior scalene muscles (m. scalenus anterior, medius, posterior).
- Fibers from C₃–C₄ control the levator scapulae muscle (m. levator scapulae).
An important structure is the ansa cervicalis (ansa cervicalis, C₁–C₃). It innervates the infrahyoid muscles: the sternohyoid (m. sternohyoideus), sternothyroid (m. sternothyroideus), and both bellies of the omohyoid muscle (m. omohyoideus). Meanwhile, some C₁ fibers travel within the hypoglossal nerve (n. hypoglossus) and give off branches to the geniohyoid (m. geniohyoideus) and thyrohyoid (m. thyrohyoideus) muscles.
Mixed branches and anastomoses
Phrenic nerve (n. phrenicus) is the most important mixed nerve of the cervical plexus. It originates from segments C₃–C₅, with the predominant contribution coming from C₄ fibers. This nerve performs a dual function:
- Motor: provides contraction of the diaphragm, which is critical for breathing.
- Sensory: innervates the pleura, pericardium, and peritoneum covering the diaphragm.
In addition, the cervical plexus (segments C₂–C₄) has communicating branches with the accessory nerve (n. accessorius). These connections are necessary to provide proprioceptive (muscle-joint) innervation to the sternocleidomastoid muscle (m. sternocleidomastoideus) and trapezius muscle (m. trapezius).
Briefly: answers to topical questions
From which branches of the spinal nerves is the cervical plexus formed?
The cervical plexus (plexus cervicalis) is formed from the anterior rami of the upper cervical spinal nerves.
- Anterior rami (rami anteriores) are formed by the four upper cervical nerves $C_1–C_4$.
- Cervical segments — the plexus is formed by the anterior rami of spinal nerves $C_1, C_2, C_3, C_4$.
Where is the cervical plexus topographically located?
The cervical plexus (plexus cervicalis) is located in the lateral region of the neck lateral to the transverse processes of the cervical vertebrae.
- Medially — lies adjacent to the prevertebral muscles.
- Laterally — borders the scalenus medius muscle (m. scalenus medius), levator scapulae muscle (m. levator scapulae), and splenius cervicis muscle (m. splenius cervicis).
- Anteriorly — the structure is covered by the sternocleidomastoid muscle (m. sternocleidomastoideus).
With which cranial nerves does the cervical plexus anastomose?
The cervical plexus (plexus cervicalis) forms anastomoses with several cranial nerves:
- Accessory nerve (n. accessorius, cranial nerve XI) — connections are made with branches of $C_2–C_4$ for proprioceptive innervation of muscles.
- Hypoglossal nerve (n. hypoglossus, cranial nerve XII) — $C_1$ fibers are incorporated into the nerve, and the descending branch participates in the formation of the ansa cervicalis.
- Facial nerve (n. facialis, cranial nerve VII) — the transverse cervical nerve connects with the cervical branch (ramus colli).
Which neck and occipital nerves are the posterior rami of the cervical spinal nerves?
The posterior rami of the cervical spinal nerves are:
- Suboccipital nerve (n. suboccipitalis) — the posterior ramus of the first cervical ($C_1$) spinal nerve.
- Greater occipital nerve (n. occipitalis major) — the posterior ramus of the second cervical ($C_2$) spinal nerve.
Class and exam questions
From which spinal cord segments is the phrenic nerve formed?
The phrenic nerve (n. phrenicus) is formed from spinal nerves at the level of C₃–C₅, with the bulk of fibers typically originating from the C₄ segment.
Which muscles receive innervation from the ansa cervicalis?
The ansa cervicalis provides motor innervation to the infrahyoid muscle group: the sternohyoid, sternothyroid, and omohyoid muscles.
How are the innervation zones of the supraclavicular nerves distributed?
The medial branches innervate the skin over the sternum and clavicle, the intermediate branches supply the upper chest and anterior shoulder, and the lateral branches supply the skin over the acromion and the lateral side of the shoulder.
What is the purpose of the connections between the cervical plexus and the accessory nerve?
Connections with the accessory nerve from segments C₂–C₄ carry proprioceptive sensitivity from the sternocleidomastoid and trapezius muscles.
What else to study on this topic
- Topography and course of the phrenic nerve branches in the thoracic cavity
- Formation and course of the suboccipital nerve (C₁)
- Interrelation of fibers of the first cervical nerve (C₁) and the hypoglossal nerve
- Anatomic boundaries and overlapping zones of the sensory occipital nerves
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