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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 .
In humans, cervical vertebrae are the smallest of the true vertebrae and can be readily distinguished from those of the thoracic or lumbar regions by the presence of a foramen (hole) in each transverse process, through which the vertebral artery, vertebral veins, and inferior cervical ganglion pass. The remainder of this article focuses upon ...
It gives off muscular branches to the Semispinalis capitis, and occasionally a twig to the back of the auricula. The lateral branch (ramus lateralis; external branch) supplies filaments to the Splenius, Longissimus capitis, and Semispinalis capitis, and is often joined by the corresponding branch of the third cervical.
Spinal nerve Typical spinal nerve location. Each spinal nerve is a mixed nerve, formed from the combination of nerve root 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.
It formed by the coalescence of four ganglia, corresponding to the four upper-most cervical nerves C1–C4. The bodies of its preganglionic sympathetic afferent neurons are located in the lateral horn of the spinal cord. Their axons enter the SCG to synapse with postganglionic neurons whose axons then exit the rostral end of the SCG and proceed ...
They are located laterally to the transverse processes between prevertebral muscles from the medial side and vertebral (m. scalenus, m. levator scapulae, m. splenius cervicis) from lateral side. There is anastomosis with accessory nerve, hypoglossal nerve and sympathetic trunk. It is located in the neck, deep to the sternocleidomastoid muscle. [5]
Within the cervical spine, most joints are innervated by the medial branch nerve (a branch of the dorsal rami) from the same levels. In other words, the facet joint between C4 and C5 vertebral segments is innervated by the C4 and C5 medial branch nerves. However, there are two exceptions:
In humans, the right and left phrenic nerves are primarily supplied by the C4 spinal nerve, but there is also a contribution from the C3 and C5 spinal nerves. From its origin in the neck, the nerve travels downward into the chest to pass between the heart and lungs towards the diaphragm.