Help the development of the site, sharing the article with friends!

VERIFIED CONTENTAuthor: lek. Tomasz Nęcki

Spinal nerves, of which there are 31 pairs in the human body, are part of the peripheral nervous system. They form complex structures, such as, for example, the cervical plexus or the brachial plexus, whose branches innervate various muscles of the torso or limbs. In addition, spinal nerves sensually innervate the body shell and also lead the fibers of the autonomic system. Knowing the extent of innervation of individual spinal nerves is important because by determining the exact location of the disorders that appear in the patient, it is possible to deduce which of these nerves has been dysfunctional.

As in the central nervous system, the cranial nerves that belong to it are distinguished, their counterpart in the peripheral nervous system isspinal nerves . Each of them begins in the spinal cord, from where the spinal nerves - via the intervertebral foramen - travel to the periphery and perform many different functions.

Spinal nerves: structure

Eachspinal nerveconsists of two roots: anterior and posterior. Within the posterior root there is a characteristic thickening, which is the spinal ganglion. This root contains sensory (afferent) fibers that conduct sensory impulses from all over the body that ultimately are directed to the structures of the central nervous system.

The task of the front root is to send efferent (centrifugal) impulses, which are generated in the central nervous system and which will eventually go to various executive organs (mainly muscle cells). Even before leaving the spinal canal, both roots connect with each other and this is when thespinal nerveis formed, which goes - through the previously mentioned intervertebral openings - to the periphery of the body.

As soon as thespinal nerveleaves the structures of the spinal canal, it releases several branches. They are:

  • front branch,
  • back branch,
  • dural branch (it goes backwards towards the spinal canal and innervates, among others, the tires inside it).

Apart from those mentioned, the branches connecting the gray ones through which connectone with a sympathetic trunk running on the lateral part of the vertebral bodies. Each of thespinal nervesis a mixed nerve, meaning it contains both sensory and motor fibers, and these nerves also carry fibers that belong to the structures of the autonomic system.

We also recommend: Spinal cord injury: causes, symptoms, treatment

Spinal nerves: quantity and division

In humans, there are 31 pairs ofspinal nerves , which are divided depending on which section of the spinal cord they depart from. Therefore, it stands out:

  • cervical spinal nerves,
  • thoracic spinal nerves,
  • lumbar spinal nerves,
  • sacral spinal nerves,
  • spinal coccygeal nerves .

Spinal nerves: cervical nerves

The cervical nerves are distinguished in a human of 8 pairs. The first nerve, the C1 nerve, comes out of the spinal canal between the occipital bone and the apical vertebra (atlas). The remainingspinal nervescervical leave the spinal canal above the vertebrae with the same numbering (meaning that e.g. the second cervical nerve comes out above the second cervical vertebra, etc.). The exception is the eighth cervical nerve, which comes out of the spinal canal between the seventh cervical and first thoracic vertebrae.

The cervical nerves form two plexuses: the first is the cervical plexus (it consists of the branches of the cervical nerves from the first to the fourth). The cervical plexus departs, among others, phrenic nerve. The second plexus, which is made up of the cervical spinal nerves, is the brachial plexus (which consists of branches originating from the fifth through eighth cervical nerves and the branches of the first thoracic spinal nerve). Various nerves that supply the upper limb derive from him - they are:

  • axillary nerve,
  • muscle-cutaneous nerve,
  • median nerve,
  • ulnar nerve,
  • radial nerve.

Spinal nerves: pectoral nerves

thoracicspinal nervesthere are 12 pairs and each of them leaves the spinal canal below the vertebrae with the same number (for example, the first spinal nerve extends to the circumference below the first thoracic vertebra). Most of all, intercostal nerves, of which there are 12 pairs in humans, depart from them.

Spinal nerves: lumbar nerves

5 pairs ofspinal nervesderive from the lumbar spinal cord. The most important structure formed by the lumbar spinal nerves is the lumbar plexus, formed mainly bythrough the branches of the first three lumbar nerves, and also through some of the branches of the fourth lumbar nerve and the branches originating from the twelfth thoracic nerve.

The branches coming from the lumbar plexus supply part of the abdominal wall (its lower section) and also (partly) the lower limb. This structure is the source of clinically important nerves such as the femoral nerve, the obturator nerve, the genitourinary nerve, and the lateral cutaneous nerve of the thigh.

Spinal nerves: sacral nerves

There are 5 pairs ofspinal nervesin the sacrum from the spinal cord. The fibers belonging to them, as well as the branches from the last lumbar nerve and the coccyge nerve, form the sacral plexus. It innervates the pelvic structures and part of the lower limb. The sciatic nerve, on the other hand, leaves the sacral plexus, from which the tibial nerve and the common peroneal nerve ultimately originate.

Spinal nerves: coccygeal nerves

Human coccygeal nerves are distinguished by one pair and the branches departing from them, as already mentioned, form together with otherspinal nervessacral plexus. In addition, the coccygeal nerve is responsible for the innervation of the skin around the coccyx.

Spinal nerves: clinical significance and disease

When discussingspinal nerves , it is impossible not to mention a related term, which is dermatomy. This term is defined as the area of ​​skin that is innervated by one spinal nerve and, for example, the fifth cervical nerve innervates the skin from the anterior part of the upper limb, the sixth nerve innervates the lateral surface of the upper limb and the thumb, and the seventh cervical nerve innervates the skin of the posterior part of the upper limb and the first two fingers.

The knowledge of dermatomes is important because knowing exactly in which part of the body the patient experiences some symptoms (e.g. sensory disturbances or muscle paresis), it is possible to suspect which spinal nerve has been damaged. In turn, the diseases of the spinal nerves are distinguished by far more than potentially suspected. Various ailments may appear in the case of oppression of these structures - this can be caused, among others, by displacement of intervertebral discs, as well as narrowing of the intervertebral gaps or fractures of the vertebrae.

Disorders of the activityof spinal nervescan also be found when there is pressure on them by, for example, neoplastic tumors developing in their surroundings. One of the best-known diseases in which the spinal nerves are compressed is sciatica.

About the authorBow. Tomasz NęckiA graduate of medicine at the Medical University of Poznań. An admirer of the Polish sea (preferablywalking along its shores with headphones in their ears), cats and books. In working with patients, he focuses on always listening to them and spending as much time as they need.

Read more from this author

Help the development of the site, sharing the article with friends!

Category:

Neurology