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Encyclopedia > Spinal nerve
Nerve: Spinal nerve
The formation of the spinal nerve from the dorsal and ventral roots
Scheme showing structure of a typical spinal nerve.
1. Somatic efferent.
2. Somatic afferent.
3,4,5. Sympathetic efferent.
6,7. Sympathetic afferent.
Latin nervi spinales
Gray's subject #208 916
MeSH Spinal+nerves
Dorlands/Elsevier n_05/12566663

The term spinal nerve generally refers to the mixed spinal nerve, which is formed from the dorsal and ventral roots that come out of the spinal cord. The spinal nerve is the bit that passes out of the vertebrae through the intervertebral foramen. All spinal nerves are part of the peripheral nervous system (PNS). Image File history File links Spinal_nerve. ... Image File history File links Gray799. ... The general somatic efferent fibers (or somatic motor fibers), efferent fibers, arise from cells in the anterior column of the spinal cord and pass out through the anterior roots to the voluntary muscles. ... The general somatic afferent fibers (or somatic sensory fibers), afferent fibers, arise from cells in the spinal ganglia and are found in all the spinal nerves, except occasionally the first cervical, and conduct impulses of pain, touch and temperature from the surface of the body through the posterior roots to... The general visceral efferent fibers (GVE or sympathetic efferent fibers), probably arise from cells in the lateral column or the base of the anterior column and emerge through the anterior roots and white rami communicantes. ... The general visceral afferent fibers (or sympathetic afferent fibers), conduct sensory impulses from the viscera through the rami communicantes and posterior roots to the spinal cord. ... For other uses, see Latin (disambiguation). ... Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. ... Elseviers logo. ... Nerves (yellow) Nerves redirects here. ... The Spinal cord nested in the vertebral column. ... A diagram of a thoracic vertebra. ... When the vertebrae are articulated with each other the bodies form a strong pillar for the support of the head and trunk, and the vertebral foramina constitute a canal for the protection of the medulla spinalis (spinal cord), while between every pair of vertebræ are two apertures, the intervertebral foramina... The peripheral nervous system or PNS, is part of the nervous system, and consists of the nerves and neurons that reside or extend outside the central nervous system (the brain and spinal cord) to serve the limbs and organs, for example. ...

Contents

Numbering

There are a total of 31 bilaterally-paired spinal nerves :

The first to seventh cervical nerves (C1 to C7) exit from the vertebral canal above the respective cervical vertebra (that is to say, C1 exits above the first cervical vertebra; C2 exits above the second, and so forth). The C8 spinal nerve exits below the seventh cervical vertebra, and all the other spinal nerves leave below their corresponding vertebra. The Cervical Nerves—The posterior division of the first cervical or suboccipital nerve is larger than the anterior division, and emerges above the posterior arch of the atlas and beneath the vertebral artery. ... The Thoracic Nerves—The medial branches (ramus medialis; internal branch) of the posterior divisions of the upper six thoracic nerves run between the Semispinalis dorsi and Multifidus, which they supply; they then pierce the Rhomboidei and Trapezius, and reach the skin by the sides of the spinous processes. ... The formation of the spinal nerve from the dorsal and ventral roots Grays Fig. ... The five sacral nerves emerge from the sacrum. ... The coccygeal nerve is the spinal nerve that corresponds to the coccyx bone. ... A diagram of a thoracic vertebra. ... In anatomy, the atlas (C1) is the topmost (first) cervical vertebra of the spine. ... The most distinctive characteristic of the seventh cervical vertebra is the existence of a long and prominent spinous process, hence the name vertebra prominens. ...


Formation of the spinal nerves

Inside the spinal cord, there is grey matter, surrounded by white matter. From out of the grey matter, two dorsal roots (one on the left side, and one on the right side) and two ventral roots emerge. (Dorsal means back, ventral means front.) As the body is symmetrical, the same thing happens on both the left and right side of the body. This happens in each vertebra of the spine. Grey matter is a major component of the central nervous system, consisting of nerve cell bodies and short nerve cell extensions/processes (axons and dendrites). ... White matter is one of the two main solid components of the central nervous system. ... penis ... In anatomy and neurology, the ventral root is the efferent motor root of a spinal nerve. ...

  • The ventral roots similarly continue out from the spinal column, and meet and mix with their corresponding dorsal nerve root at a point after the ganglion.

At this point, the combination of the dorsal roots and ventral roots is called a mixed spinal nerve. The mechanism of the reflex arc In the nervous system, afferent neurons--otherwise known as sensory or receptor neurons--carry nerve impulses from receptors or sense organs toward the central nervous system. ... Somatic sensation consists of the various sensory receptors that trigger the experiences labelled as touch or pressure, temperature (warm or cold), pain (including itch and tickle), and the sensations of muscle movement and joint position including posture, movement, and facial expression (collectively also called proprioception). ... An axon or nerve fiber, is a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neurons cell body or soma. ... In the nervous system, efferent nerves otherwise known as motor or effector neuron carry nerve impulses away from the central nervous systemto effectors - either muscles or glands. ... In vertebrates, motoneurons (also called motor neurons) are efferent neurons that originate in the spinal cord and synapse with muscle fibers to facilitate muscle contraction and with muscle spindles to modify proprioceptive sensitivity. ... An axon or nerve fiber, is a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neurons cell body or soma. ... This is a dorsal root ganglion (DRG) from a chicken embryo (around stage of day 7) after incubation overnight in NGF growth medium stained with anti-neurofilament antibody. ...


Fate of the spinal nerve

After the dorsal and ventral roots fuse to form a spinal nerve, the nerve bifurcates into dorsal and ventral primary rami. Each primary ramus has two branches.


Dorsal

  • The dorsal primary ramus supplies the muscles and sensory nerves of the back.

The two main branches are a lateral and medial branch. The posterior (or dorsal) branches (or divisions) of the spinal nerves are as a rule smaller than the anterior divisions. ...


Ventral

  • The ventral primary ramus supplies the rest of the body wall.

The two main branches are an anterior and lateral cutaneous branch. In addition, the anterior cutaneous bifurcates, forming a medial and lateral branch, while the lateral cutaneous branch splits into an anterior and posterior branch. These secondary and tertiary branches themselves typically have muscular and sensory branches that innervate the body wall. The ventral ramus (anterior ramus, anterior branch, anterior divisions of the spinal nerves) supply the antero-lateral parts of the trunk, and the limbs; they are for the most part larger than the posterior divisions. ...


The ventral primary rami also give rise to the roots of the various nervous plexuses (e.g. the brachial plexus), which become the sensory and motor nerves of the limbs. PLEXUS (Physics Learning EXperience Using Software) is a name of project that was started by Vibor Cipan, physics student form Croatia and it is based on utilization of usage of computer technology to enhance learning of physics. ... The brachial plexus is an arrangement of nerve fibres (a plexus) running from the spine (vertebrae C5-T1), through the neck, the axilla (armpit region), and into the arm. ...


Before forming the plexuses, the ventral rami have two branches leading to a sympathetic ganglion. These ganglia connect to the one above and below them, forming the sympathetic chain. Grays FIG. 838– The right sympathetic chain and its connections with the thoracic, abdominal, and pelvic plexuses. ... The Sympathetic Chain is a series of interconnected sympathetic ganglia, belonging to the autonomic nervous system. ...


Importance of the spinal nerves

The muscles that one particular spinal root supplies are that nerve's myotome, and the dermatomes are the areas of sensory innervation on the skin for each spinal nerve. In vertebrate embryonic development, a group of tissues formed from somites that develop into the body wall muscle. ... Dermatome has three meanings: in surgery, a surgical instrument used for slicing skin in order to perform skin grafts. ...


This is of great importance in the diagnosis of neurological disorders, as lesions of one or more nerve roots result in typical patterns of neurologic defects (muscle weakness, loss of sensation) that allow localisation of the causating lesion. In general, a diagnosis (plural diagnoses) has two distinct dictionary definitions. ... Neurology is a branch of medicine dealing with disorders of the central and peripheral nervous systems. ... See also Muscle Atrophy Muscle weakness (or lack of strength) is a direct term for It is the inability to exert force with ones muscles to the degree that would be expected given the individuals general physical fitness. ...


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