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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. [1] [2] These are grouped into the corresponding cervical, thoracic, lumbar, sacral and coccygeal regions of the spine. [1]
The C8 nerve contributes to the motor innervation of many of the muscles in the trunk and upper limb. Its primary function is the flexion of the fingers, and this is used as the clinical test for C8 integrity, in conjunction with the finger jerk reflex.
The spinal accessory nerve crosses laterally in the middle part of the muscle and the dorsal scapular nerve may lie deep to or pass through it. [ 4 ] The levator scapulae may lie deep to the sternocleidomastoid at its origin, deep or adjacent to the splenius capitis at its origin and mid-portion, and deep to the trapezius in its lower portion.
The glossopharyngeal nerve; The vagus nerve; The accessory nerve; The hypoglossal nerve; The spinal nerves. The posterior divisions; The anterior divisions; The thoracic nerves; The lumbosacral plexus; The sacral and coccygeal nerves; The sympathetic nerves. The cephalic portion of the sympathetic system; The cervical portion of the sympathetic ...
The diameter of the spinal cord ranges from 13 mm (1 ⁄ 2 in) in the cervical and lumbar regions to 6.4 mm (1 ⁄ 4 in) in the thoracic area. The spinal cord functions primarily in the transmission of nerve signals from the motor cortex to the body, and from the afferent fibers of the sensory neurons to the sensory cortex.
The spinal nerves arise from the spinal column. The top section of the spine is the cervical section, which contains nerves that innervate muscles of the head, neck and thoracic cavity, as well as transmit sensory information to the CNS. The cervical spine section contains seven vertebrae, C-1 through C-7, and eight nerve pairs, C-1 through C-8.
There is anastomosis with accessory nerve, hypoglossal nerve and sympathetic trunk. It is located in the neck, deep to the sternocleidomastoid muscle. [5] The branches of the cervical plexus emerge from the posterior triangle at the nerve point, a point which lies midway on the posterior border of the sternocleidomastoid.
Cervical spinal nerve 4, also called C4, is a spinal nerve of the cervical segment. It originates from the spinal cord above the 4th cervical vertebra (C4). It contributes nerve fibers to the phrenic nerve , the motor nerve to the thoracoabdominal diaphragm .