出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/09/27 20:31:34」(JST)
| 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. |
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| Latin | nervus spinalis |
| Gray's | subject #208 916 |
| Code | TA A14.2.00.027 |
| MeSH | Spinal+nerves |
The term spinal nerve generally refers to a mixed spinal nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. Humans have 31 left-right pairs of spinal nerves, each roughly corresponding to a segment of the vertebral column: 8 cervical spinal nerve pairs (C1-C8), 12 thoracic pairs (T1-T12), 5 lumbar pairs (L1-L5), 5 sacral pairs (S1-S5), and 1 coccygeal pair. The spinal nerves are part of the peripheral nervous system (PNS).
Each spinal nerve is formed by the combination of nerve fibers from the dorsal and ventral roots of the spinal cord. The dorsal roots carry afferent sensory axons, while the ventral roots carry efferent motor axons. The spinal nerve emerges from the spinal column through an opening (intervertebral foramen) between adjacent vertebrae. This is true for all spinal nerves except for the first spinal nerve pair, which emerges between the occipital bone and the atlas (the first vertebra). Thus the cervical nerves are numbered by the vertebra below, except C8, which exists below C7 and above T1. The thoracic, lumbar, and sacral nerves are then numbered by the vertebra above. In the case of a lumbarized S1 vertebra (aka L6) or a sacralized L5 vertebra, the nerves are typically still counted to L5 and the next nerve is S1.
Outside the vertebral column, the nerve divides into branches. The dorsal ramus contains nerves that serve the dorsal portions of the trunk carrying visceral motor, somatic motor, and somatic sensory information to and from the skin and muscles of the back (epaxial muscles). The ventral ramus contains nerves that serve the remaining ventral parts of the trunk and the upper and lower limbs (hypaxial muscles) carrying visceral motor, somatic motor, and sensory information to and from the ventrolateral body surface, structures in the body wall, and the limbs. The meningeal branches (recurrent meningeal or sinuvertebral nerves) branch from the spinal nerve and re-enter the intervertebral foramen to serve the ligaments, dura, blood vessels, intervertebral discs, facet joints, and periosteum of the vertebrae. The rami communicantes contain autonomic nerves that serve visceral functions carrying visceral motor and sensory information to and from the visceral organs.
Some ventral rami merge with adjacent ventral rami to form a nerve plexus, a network of interconnecting nerves. Nerves emerging from a plexus contain fibers from various spinal nerves, which are now carried together to some target location. Major plexuses include the cervical, brachial, lumbar, and sacral plexuses.
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. Lesions of one or more nerve roots result in typical patterns of neurologic defects (muscle weakness, abnormal sensation, changes in reflexes) that allow localization of the causeating lesion.
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| リンク元 | 「脊髄神経」 |
| 関連記事 | 「spinal」「nerve」「spin」 |
| 支配神経根 | 責任椎間高位 | 深部反射 | 感覚領域 | 支配筋 | 支配運動 |
| C5 | C4-5 | 三角筋腱反射、上腕二頭筋腱反射 | 上腕外側 | 三角筋 | 肩の外転 |
| C6 | C5-6 | 上腕二頭筋腱反射、腕橈骨筋腱反射 | 前腕外側、1-2指 | 上腕二頭筋 | 肘屈曲、手関節背屈 |
| C7 | C6-7 | 上腕三頭筋腱反射 | 3指 | 上腕三頭筋 | 肘伸展、手関節掌屈 |
| C8 | C7-C8 | なし | 4-5指 | 指屈筋 | 手指開閉 |
| 支配神経根 | 責任椎間高位 | 深部反射 | 感覚領域 | 支配筋 |
| L4 | L3-4 | 膝蓋腱反射 | 膝蓋骨の内側近辺 | 大腿四頭筋 |
| L5 | L4-5 | 膝蓋骨下外側から母趾にかけて下方に斜行 | 前脛骨筋、長母趾伸筋、長趾伸筋 | |
| S1 | L5-S1 | アキレス腱反射 | 小趾 | 下腿三頭筋、長母趾屈筋、長趾屈筋 |