coccygeal nerve

Examples of coccygeal nerve in the following topics:

• Overview of the Spinal Nerves

  • Humans have 31 left–right pairs of spinal nerves, each roughly corresponding to a segment of the vertebral column: eight cervical spinal nerve pairs (C1–C8), 12 thoracic pairs (T1–T12), five lumbar pairs (L1–L5), five sacral pairs (S1–S5), and one coccygeal pair.
  • The posterior distribution of the cervical nerves includes the suboccipital nerve (C1), the greater occipital nerve (C2), and the third occipital nerve (C3).
  • The subcostal nerve comes from nerve T12, and runs below the twelfth rib.
  • The coccygeal nerve is the 31st pair of spinal nerves and arises from the conus medullaris.
  • Its anterior root helps form the coccygeal plexus.

• Sacral and Coccygeal Plexuses

  • The sacral plexus is a nerve plexus that provides motor and sensory nerves for the posterior thigh, most of the lower leg, the entire foot, and part of the pelvis.
  • The band itself is continued as the sciatic nerve, which splits on the back of the thigh into the tibial nerve and the common fibular nerve.
  • The coccygeal plexus originates from the S4, S5, and Co1 spinal nerves.
  • The only nerve in this plexus is the anococcygeal nerve, which serves sensory innervation of the skin in the coccygeal region.
  • Diagram of the sacral plexus showing the various anterior and posterior nerve branches that arise from each lumbar and sacral nerve.

• Function and Physiology of the Spinal Nerves

  • Each pair of spinal nerves roughly correspond 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.
  • These include the greater occipital nerve that provides sensation to the back of the head, the lesser occipital nerve that provides sensation to the area behind the ears, the greater auricular nerve, and the lesser auricular nerve.
  • The phrenic nerve arises from nerve roots C3, C4, and C5.
  • The anterior divisions of the lumbar, sacral, and coccygeal nerves form the lumbosacral plexus, the first lumbar nerve being frequently joined by a branch from the twelfth thoracic.
  • PNS nerves are involved in the erection of genital tissues via the pelvic splanchnic nerves 2–4.

• Sympathetic Nervous System

  • An example of a sympathetic ganglion in a thoracic nerve is shown in .
  • The chain extends from the upper neck down to the coccyx, forming the unpaired coccygeal ganglion.
  • Preganglionic nerves from the spinal cord synapse at one end of the chain ganglia and the postganglionic fibre extends to an effector, typically a visceral organ in the thoracic cavity.
  • Neurons of the collateral ganglia, also called the prevertebral ganglia, receive input from the splanchnic nerves and innervate organs of the abdominal and pelvic region.
  • This intercostal nerve shows the sympathetic ganglion at the top left.

• Plexuses

  • A nerve plexus is a network of intersecting nerves  that serve the same part of the body.
  • A nerve plexus is a network of intersecting nerves; multiple nerve plexuses exist in the body.
  • Nerve plexuses are composed of afferent and efferent fibers that arise from the merging of the anterior rami of spinal nerves and blood vessels.
  • The coccygeal plexus serves a small region over the coccyx and originates from S4, S5, and Co1 spinal nerves.
  • The lumbar plexus is comprised of the ventral rami of the lumbar spinal nerves (L1–L5) and a contribution from thoracic nerve (T12).

• Autonomic Ganglia

  • They are essentially a junction between autonomic nerves originating from the central nervous system and autonomic nerves innervating their target organs in the periphery.
  • Nerves that carry signals towards the brain are known as afferent nerves.
  • The distal section of the axon may either be a bare nerve ending or encapsulated by a structure that helps relay specific information to a nerve.
  • The chain extends from the upper neck down to the coccyx, forming the unpaired coccygeal ganglion.
  • As a result, the postsynaptic parasympathetic nerve fibers are very short.

• The Spine

  • There are normally 33 vertebrae in humans, including the five that are fused to form the sacrum, the four coccygeal bones that form the tailbone, and the others separated by intervertebral discs.
  • Between each pair of vertebrae are two small openings called intervertebral foramina through which the spinal nerves exit.

• Trochlear (IV) Nerve

  • The trochlear nerve (cranial nerve IV) is a motor nerve that innervates a single muscle: the superior oblique muscle of the eye.
  • The trochlear nerve (cranial nerve IV) is a motor nerve that innervates a single muscle: the superior oblique muscle of the eye.
  • The trochlear nerve is unique among the cranial nerves in several respects.
  • Other than the optic nerve (cranial nerve II), it is the only cranial nerve that decussates (crosses to the other side) before innervating its target.
  • Lesions of all other cranial nuclei affect the ipsilateral side (except of course the optic nerve, cranial nerve II, which innervates both eyes).

• Accessory (XI) Nerve

  • The accessory nerve (cranial nerve XI) controls the muscles of the shoulder and neck.
  • The accessory nerve (cranial nerve XI) controls the sternocleidomastoid and trapezius muscles of the shoulder and neck.
  • Unlike the other 11 cranial nerves, the accessory nerve begins outside the skull.
  • Due to its unusual course, the accessory nerve is the only nerve that enters and exits the skull.
  • However, more modern characterizations of the nerve regard the cranial component as separate and part of the vagus nerve.

• Brief Overview of Cranial Nerves

  • Cranial nerves are the nerves that emerge directly from the brain (including the brainstem).
  • The terminal nerves, olfactory nerves (I) and optic nerves (II) emerge from the cerebrum or forebrain, and the remaining ten pairs arise from the brainstem, which is the lower part of the brain.
  • The optic nerve (II): This nerve carries visual information from the retina of the eye to the brain.
  • The abducens nerve (VI): A motor nerve that innervates the lateral rectus muscle of the eye, which controls lateral movement.
  • The hypoglossal nerve (XII): This nerve controls the tongue movements of speech, food manipulation, and swallowing.