thoracic spinal nerves

Examples of thoracic spinal nerves in the following topics:

• Branches of Spinal Nerves

  • The spinal nerves branch into the dorsal ramus, ventral ramus, the meningeal branches, and the rami communicantes.
  • 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.
  • The meningeal branches (recurrent meningeal or sinuvertebral nerves): These 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.
  • This diagram depicts the course and branches of a typical thoracic spinal nerve.

• Intercostal Nerves

  • The anterior divisions of the thoracic spinal nerves (T1–T11) are called the intercostal nerves.
  • The intercostal nerves are part of the somatic nervous system and arise from anterior divisions (rami anteriores, ventral divisions) of the thoracic spinal nerves T1 to T11.
  • They differ from the anterior divisions of the other spinal nerves in that each pursues an independent course without plexus formation.
  • The anterior division of the first thoracic nerve divides into two branches:
  • The anterior divisions of the second, third, fourth, fifth, and sixth thoracic nerves, and the small branch from the first thoracic, are confined to the walls of the thorax and are named thoracic intercostal nerves.

• Brachial Plexus

  • The brachial plexus is formed by the four lower cervical spinal nerves and the first thoracic spinal nerve.
  • The brachial plexus is a network of nerve fibers that run from the spine that are formed by the ventral rami of the lower four cervical and first thoracic nerve roots (C5–C8, T1).
  • It is a collection of nerves passing through the cervico-axillary canal to reach the axilla and innervate the brachium, the antebrachium, and the hand.
  • The brachial plexus is responsible for cutaneous and muscular innervation of the entire upper limb, with two exceptions: the trapezius muscle is innervated by the spinal accessory nerve (CN XI) and an area of skin near the axilla is innervated by the intercostobrachial nerve.
  • Five roots: The five anterior rami of the spinal nerves, after they have given off their segmental supply to the muscles of the neck.

• Function and Physiology of the Spinal Nerves

  • Spinal nerves connect the brain and spinal cord to the limbs and organs of the body.
  • 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.
  • 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.
  • The last four cervical spinal nerves, C5 through C8, and the first thoracic spinal nerve, T1, combine to form the brachial plexus, or plexus brachialis, a tangled array of nerves, splitting, combining and recombining to form the nerves that subserve the upper limb region and upper back.
  • Manages heart control via dedicated cardiac branches of the vagus and thoracic spinal accessory nerves.

• Overview of the Spinal Nerves

  • The term spinal nerve generally refers to a mixed spinal nerve that 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: 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.
  • Each spinal nerve is formed by the combination of nerve fibers from the dorsal and ventral roots of the spinal cord.
  • The thoracic, lumbar, and sacral nerves are then numbered by the vertebra above.
  • The intercostal nerves come from thoracic nerves T1–T11, and run between the ribs.

• Plexuses

  • Nerve plexuses are composed of afferent and efferent fibers that arise from the merging of the anterior rami of spinal nerves and blood vessels.
  • There are five spinal nerve plexuses—except in the thoracic region—as well as other forms of autonomic plexuses, many of which are a part of the enteric nervous system.
  • The brachial plexus is formed by the ventral rami of C5–C8 and the T1 spinal nerves, and lower and upper halves of the C4 and T2 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).
  • Cervical (C5–C8) and thoracic (T1) nerves comprise the brachial plexus, which is a nerve plexus that provides sensory and motor function to the shoulders and upper limbs.

• Overview of the Spinal Cord

  • The spinal cord is divided into cervical, thoracic, and lumbar regions.
  • The spinal nerves of the thoracic region supply the thorax and abdomen.
  • Thirty-one pairs of spinal nerves (sensory and motor) branch from the human spinal cord.
  • Each spinal nerve is formed from the combination of nerve fibers from its posterior and anterior roots.
  • Relationship between the spinal cord and vertebral column, delineating the cervical, thoracic, and lumbar sections.

• Dermatomes

  • A dermatome is an area of skin that is supplied by a single spinal nerve, and a myotome is a group of muscles that a single spinal nerve root innervates.
  • A dermatome is an area of skin that is supplied by a single spinal nerve .
  • There are eight cervical nerves, twelve thoracic nerves, five lumbar nerves and five sacral nerves.
  • A myotome is the group of muscles that a single spinal nerve root innervates.
  • Results may indicate lesions to the spinal cord nerve root, or intervertebral disc herniation that presses on the spinal nerve roots.

• The Spine

  • Situated in the dorsal aspect of the torso and separated by intervertebral discs, it houses and protects the spinal cord in its spinal canal.
  • These parts together enclose the vertebral foramen that contains the spinal cord.
  • Between each pair of vertebrae are two small openings called intervertebral foramina through which the spinal nerves exit.
  • It ends at the middle of the second thoracic vertebra.
  • The thoracic curve convexes dorsally, begins at the middle of the second thoracic vertebra, and ends at the middle of the 12th thoracic vertebra.

• Injuries to the Phrenic Nerves

  • The phrenic nerve is a nerve that originates in the neck and passes down between the lung and the heart to reach the diaphragm.
  • The phrenic nerves contain motor, sensory, and sympathetic nerve fibers.
  • Pain arising from structures served by the phrenic nerve is often "referred" to other somatic regions served by spinal nerves C3-C5.
  • The phrenic nerve must be identified during thoracic surgery and preserved.
  • The phrenic nerve and its relations with the vagus nerve.