Spinal nerve

A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral 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.A portion of the spinal cord, showing its right lateral surface. The dura is opened and arranged to show the nerve roots.Distribution of the cutaneous nerves. Ventral aspect.Distribution of the cutaneous nerves. Dorsal aspect.The spinal cord with dura cut open, showing the exits of the spinal nerves.The spinal cord showing how the anterior and posterior roots join in the spinal nerves.A longer view of the spinal cord.Projections of the spinal cord into the nerves (red motor, blue sensory).Projections of the spinal cord into the nerves (red motor, blue sensory).Schematic diagram of cervical plexus.Cerebrum. Inferior view. Deep dissection.Cerebrum. Inferior view. Deep dissection.Spinal nerves. Spinal cord and vertebral canal. Deep dissection. A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral 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. Each spinal nerve is a mixed nerve, formed from the combination of nerve fibers from its dorsal and ventral roots. The dorsal root is the afferent sensory root and carries sensory information to the brain. The ventral root is the efferent motor root and carries motor information from the brain. 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 (C1), which emerges between the occipital bone and the atlas (the first vertebra). Thus the cervical nerves are numbered by the vertebra below, except spinal nerve C8, which exists below vertebra C7 and above vertebra 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 posterior portions of the trunk carrying visceral motor, somatic motor, and somatic sensory information to and from the skin andmuscles of the back (epaxial muscles). The ventral ramus contains nerves that serve the remaining anterior 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 anterior rami merge with adjacent anterior 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 cervical nerves are the spinal nerves from the cervical vertebrae in the cervical segment of the spinal cord. Although there are seven cervical vertebrae (C1-C7), there are eight cervical nerves C1–C8. All cervical nerves except C8 emerge above their corresponding vertebrae, while the C8 nerve emerges below the C7 vertebra. Elsewhere in the spine, the nerve emerges below 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 brachial plexus (C5-T1). The cervical nerves innervate the sternohyoid, sternothyroid and omohyoid muscles. A loop of nerves called ansa cervicalis is part of the cervical plexus. The thoracic nerves are the twelve spinal nerves emerging from the thoracic vertebrae. Each thoracic nerve T1 -T12 originates from below each corresponding thoracic vertebra. Branches also exit the spine and go directly to the paravertebral ganglia of the autonomic nervous system where they are involved in the functions of organs and glands in the head, neck, thorax and abdomen.