Spinal Cord Spinal Nerves

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Spinal CordSpinal Nerves
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Spinal Cord

• Part of the CNS
• About 18 inches long
• Extends from the foramen magnum to the end of L1
• Main pathway for information flow to and from the
  brain

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Spinal Cord Histology / Structure
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Dorsal root ganglia

• Sensory neuron cells bodies
• These are unipolar neurons in structure

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Gross Anatomy of the Spinal Cord

• Cord is divided into cervical, thoracic, lumbar
  and sacral segments
• Cervical and lumbar enlargements
• Covered by same membranes as the brain
• At about L1 the cord divides into many long
  ventral and dorsal roots called the cauda equina
  (horses tail)
• Each spinal segment has a pair of dorsal root
  ganglia (sensory neuron cell bodies)
• Dorsal root enters the cord, ventral root leaves
  the cord

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Spinal cord and meninges
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Spinal Cord and Meninges
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Ganglia and roots

• Dorsal root ganglia sensory neuron cell bodies
• Dorsal root sensory input
• Ventral root motor output
• Spinal nerve - mixed

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Epidural analgesia

• Pain medication placed into the epidural space
• Often used to block pain associated with child
  birth
• Continuous infusion
• Blocks pain not muscle activity

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Spinal Cord White Matter

• White matter is divided into columns
• Columns contain TRACTS composed of axons of
  similar structural and functional characteristics
• Specific tracts convey either sensory or motor
  commands
• All axons in a tract relay information in the
  same direction
• ASCENDING TRACTS relay sensory information toward
  the brain
• DESCENDING TRACTS relay motor information into
  the spinal cord

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Spinal Cord Gray Matter

• Gray matter is organized into nuclei neuron
  cell bodies
• Sensory nuclei receive and relay sensory
  information
• Motor nuclei send out commands to peripheral
  effectors, skeletal muscles

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Spinal Nerves

• 31 pairs of spinal nerves
• C1-C8
• T1-T12
• L1-L5
• S1-S5

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Nerve Structure

• Nerve is divided into fascicles
• Outer covering of the nerve is the epineurium
• Each fascicle is surrounded by the perineurium
• Each axon in the fascicle is covered by the
  endoneurium

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Nerve Distribution - motor
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Nerve Distribution - sensory
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Spinal Cord Injuries

• Two general types of injuries
• Complete - no function below the affected area of
  the cord
• C1 - C3 injury breathing affected - respirator
• C4 - C7 quadriplegia (arms and legs)
• Incomplete - some function below the affected
  area of the cord
• Thoracic area and below - paraplegia (legs)

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Cause of Spinal Cord Injuries

• Sudden traumatic blow to spine that fractures or
  dislocates vertebrae
• Bone fragments, disc material bruise or tear the
  spinal cord tissue
• Cord swells, blood supply cells can stop, neurons
  die, cord is damaged beyond repair

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Treatment of Spinal Cord Injuries

• Minimize further injury
• Realign spine and immobilize (surgery)
• Steroid medication to reduce swelling
• Methylprednisolone in first 8 hours reduces
  swelling, inflammation and nerve cell damage
• Rehabilitation
• Dealing with long term complications

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Nerve Plexuses

• Ventral rami (branches) of various spinal nerves
  blend together to form an interwoven network of
  nerves, nerve plexus
• Four major plexuses
• Cervical
• Brachial
• Lumbar
• Sacral

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Cervical Plexus
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Cervical plexus

• Ventral rami of C1-C4 with a few fibers from C5
• Innveration of muscles of the neck, shoulder and
  upper breast
• Phrenic nerve innervation of diaphragm

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Brachial plexus
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Brachial plexus

• Axillary nerve
• Radial nerve
• Musculocutaneous nerve
• Median nerve
• Ulnar nerve

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Brachial plexus
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Lumbar plexus and Sacral plexus
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Major spinal nerves from the lumbar and sacral
plexus
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Nerves of the lower extermity
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Reflex arc