The cervical spinal nerves, also known simply as cervical nerves, are 8 of as many cervical vertebrae that arise from the spinal cord. These 8 vertebrae, numbered from C1 to C8, originate at the base of the skull.
All cervical spinal nerves , except C1 (which normally has no dorsal root), are associated with a dermatome. A dermatome is an area of the skin innervated by a spinal nerve.
The spinal nerves
As we already know, the cervical nerves encompass 8 spinal nerves. The latter, in turn, are a set of nerves (between 31 and 33) belonging to the somatic nervous system, whose function is to innervate the different parts of the body.
They consist of a sensitive branch and a motor branch. The former carries the information of sensitivity to the muscles it innervates. As for the motor nerves, however, they allow the automatic contraction of the muscles. They therefore play their role precisely thanks to this combination. The spinal nerves, which include the cervical spinal nerves, are as follows:
- 8 pairs of cervical nerves (C1-C8).
- 12 thoracic nerves (T1-T12).
- Coccygeus nerve.
- 5 sacral nerves (S1-S5).
- 5 lumbar nerves (L1-L5).
The cervical spinal nerves, belonging to the group of spinal nerves, share the same characteristics. In the first place, as already mentioned, these are mixed nerves, that is, composed of both sensory and motor fibers. Second, all divisions of the ventral branch, with the exception of the thoracic branch (T1 to T12), form several branches known as nerve plexuses. These plexuses are present in the cervical, brachial and lumbo-sacral areas.
Within these interconnected branches, the fibers that originate in the ventral branch intersect and redistribute themselves in such a way that each resulting branch contains the fibers of the different spinal nerves. Those coming from each ventral branch travel to the periphery of the body through different paths in the branches.
For this reason, each muscle of one extremity will receive the innervation of more than one spinal nerve. Consequently, in the event of damage to one of the spinal cord segments or nerves, the extremity will not be completely unusable.
The ventral branches of the first four spinal nerves form the cervical plexus. Its ramifications are cutaneous nerves that innervate the skin of the following areas by transmitting sensory impulses:
- Back of the head.
There are also ramifications that complement the anterior neck muscles. The phrenic nerve also arises from the cervical plexus, which groups together the fibers that come mainly from C3 and C4. The phrenic nerve travels up the chest to innervate the diaphragm, the most important muscle in breathing.
The ventral branches of the cervical spinal nerves C5 and C8, together with the primary anterior branch T1, form the brachial plexus. Its ramifications are responsible for the innervation of the shoulders and upper limbs.
Finally, the dorsal branches are responsible for the innervation of the cervical facets. From these branches depart the ramifications of the muscles of the head and neck, as well as the skin between the vertex (upper surface of the head) and the shoulders.
Subdivision of the cervical nerves
Like the other spinal nerves, the cervical nerves divide into the dorsal and ventral branches after leaving the vertebral canal. Once outside the spinal cord, the ventral and dorsal roots join together to form the dorsal ganglion (or spinal ganglion). Later, these ganglia are divided into:
- Ventral or anterior branch: it is a large and thick branch. It crosses, divides by anastomosis with the anterior branches of other spinal nerves to form, as we have seen, the cervical plexus.
- Dorsal or posterior branch: it is the posterior branch of the trunk. It is a much thinner branch than the previous one.
In conclusion, the cervical nerves are an important part of the nervous system. It is necessary to know them and take care of them, as otherwise they could cause numerous ailments.