Index
It is a mixed nerve that carries motor, sensory, and autonomic signals between the spinal cord and the body.
There are 31 pairs of spinal nerves in the human body, one on each side of the spinal column. These are grouped into the corresponding cervical, thoracic, lumbar, sacral, and coccygeal regions of the spine .
There are eight pairs of cervical nerves, twelve pairs of thoracic nerves, five pairs of lumbar nerves, five pairs of sacral nerves, and one pair of coccygeal nerves. The spinal nerves are part of the peripheral nervous system.
Regional nerves
Cervical nerves
The cervical nerves are the spinal nerves of the cervical vertebrae in the cervical segment of the spinal cord. Although there are seven cervical vertebrae (C1-C7), there are eight C1 – C8 cervical nerves.
All cervical nerves except C8 emerge above their corresponding vertebrae, while the C8 nerve emerges below the C7 vertebra. In another part of the spinal column, the nerve emerges under the vertebra with the same name.
The posterior distribution includes the suboccipital nerve (C1), the greater occipital nerve (C2), and the third occipital nerve (C3). The anterior distribution includes the cervical plexus (C1-C4) and the brachial plexus (C5-T1).
The cervical nerves innervate the sternohyoid, sternothyroid, and omohyoid muscles.
A loop of nerves called the ansa cervicalis is part of the cervical plexus.
Thoracic nerves
The thoracic nerves are the twelve spinal nerves that emerge from the thoracic vertebrae. Each T1-T12 thoracic nerve originates from below each corresponding thoracic vertebra.
The branches also leave the spinal column and go directly to the paravertebral ganglia of the autonomic nervous system, where they participate in the functions of the organs and glands of the head, neck, chest and abdomen.
Lumbar nerves
The lumbar nerves are the five spinal nerves that leave the lumbar vertebrae. They are divided into posterior and anterior divisions.
Posterior divisions: The medial branches of the posterior divisions of the lumbar nerves run near the articular processes of the vertebrae and end in the multifidus muscle.
The laterals supply the erector spinae muscles.
The upper three emit cutaneous nerves that traverse the latissimus dorsi aponeurosis at the lateral border of the erector spinae muscles and descend through the posterior part of the iliac crest to the skin of the buttocks, and some of their branches go as far as the level of the greater trochanter.
Anterior division : The anterior divisions of the lumbar nerves (anterior rami) increase in size from above to below. They are joined, close to their origins, by gray communicating branches of the lumbar ganglia of the sympathetic trunk.
These branches consist of long, thin branches that accompany the lumbar arteries around the sides of the vertebral bodies.
Sacral nerves
The sacral nerves are the five pairs of spinal nerves that exit from the sacrum at the lower end of the spinal column. The roots of these nerves begin within the spinal column at the level of the L1 vertebra, where the cauda equina begins, and then descend to the sacrum.
There are five pairs of sacral nerves, half of them arising through the sacrum on the left side and half on the right side. Each nerve emerges in two divisions, one division through the anterior sacral floor and the other division through the posterior sacral foramina.
The nerves are divided into branches and the branches of different nerves join each other, some of them also join with lumbar or coccygeal nerve branches.
These nerve anastomoses form the sacral plexus and the lumbosacral plexus. The branches of these plexuses give rise to nerves that supply much of the hip, thigh, leg, and foot.
The sacral nerves have both afferent and efferent fibers, so they are responsible for part of the sensory perception and movements of the lower extremities of the human body.
From S2, S3, and S4 arise the pudendal nerve and parasympathetic fibers whose electrical potential supplies the descending colon and rectum, the urinary bladder, and the genital organs.
These pathways have both afferent and efferent fibers and, in this way, are responsible for the conduction of sensory information from these pelvic organs to the central nervous system (CNS) and motor impulses from the CNS to the pelvis that control the movements of these pelvic organs. .
Coccygeal nerve
The coccygeal nerve is the 31st pair of spinal nerves. It arises from the medullary cone and its anterior root helps to form the coccygeal plexus. It does not divide into a medial and lateral branch. It is distributed to the skin over the back of the coccyx.
