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| Nerve: Spinal nerve | |
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| The formation of the spinal nerve from the dorsal and ventral roots | |
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| Scheme showing structure of a typical spinal nerve. 1. Somatic efferent. 2. Somatic afferent. 3,4,5. Sympathetic efferent. 6,7. Sympathetic afferent. |
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| 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).
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.
- The dorsal roots contain afferent sensory axons. The dorsal roots of each side continue outwards, along the way forming a dorsal root ganglion (also called a spinal ganglion).
- The ventral roots contain efferent motor axons. Similar to the dorsal roots, the ventral roots 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.
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.
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.
External links
- spinal+nerves at eMedicine Dictionary
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Wikipedia content modification information:
- This page was last modified on 4 September 2008, at 12:36.
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