Leture 20 - Spinal Cord Anatomy

• Spinal cord


  • Starts at the foramen magnum = big hole, the opening at the base of the skull
  • Ends at the inferior border of the 1st lumbar vertebra L1
• Spinal cord


  • Within a sack, made of meninges that fills the spinal cavity
  • Spinal cavity within the vertebrae
• Dorsal side


  Bumpy side that we can feel
• Ventral side


  Contains body of vertebrae, the belly
• Spinal canal


  The space in the middle, where the spinal cord goes
• Spinal cord and sack of meninges are contained within the spinal canal
• Posterior, dorsal side


  Contains the spinous process
• Anterior, ventral side


  Contains the body of the vertebrae
• Non-neural structures associated with the spinal cord

  • Extends within a meningeal sac, filled with cerebrospinal fluid (CSF) that provides cushioning
  • The end is a tapered cone called the conus medularis, this is non-neural tissue
  • The filum terminale extends from the conus medularis to the end of the meningeal sack at the end of the spinal cavity, made of fibrous, non-neural tissue
• Spinal nerves


  The spinal cord has 31 segments, meaning these 31 pairs of spinal nerves, each one associated with a specific segment
• Spinal nerves


  • 8 pairs of Cervical
  • 12 pairs of Thoracic
  • 5 pairs of Lumbar
  • 5 pairs of Sacral
  • 1 pair of Coccygeal
• Spinal nerves - exit points

  • Spinal nerves are named by the vertebra they exit below
  • ONE EXCEPTION - The first cervical spinal nerve exits between the skull and first cervical vertebra
  • Spinal nerves exit the vertebral column at the level appropriate to their origin from the spinal cord
  • Lumbar and sacral spinal nerves need to grow quite a long way inferior-ally to exit at the appropriate vertebrae, resulting in the Cauda Equina (horses tail)
• Spinal cord


  A long structure made up of repeating units called spinal nerves
• Indentations in the spinal cord

  A small indentation is called the sulcus (furrow), a deep sulcus is called a fissure
• Posterior (dorsal) median sulcus

  A sulcus in the middle of the dorsal side
• Anterior (ventral) median fissure


  A fissure in the middle of the ventral side
• Central canal


  The hole in the middle of the spinal cord
• Grey matter


  The butterfly shaped structure containing cell bodies
• White matter


  Surrounds the grey matter, contains bundles of axons that run the length of the spinal cord
• Central Nervous System (CNS)

  Contains the spinal cord, all other structures are a part of the Peripheral Nervous System (PNS)
• Dorsal grey matter


  Called the dorsal horn
• Ventral grey matter


  Called the ventral horn
• Lateral grey matter


  Called the lateral horn
• Dorsal white matter


  Called the dorsal column (axons)
• Ventral white matter


  Called the ventral column (axons)
• Lateral white matter


  Called the lateral column (axons)
• Sensory afferent information


  Comes in from the dorsal side
• Motor efferent information


  Leaves from the ventral side, through the ventral roots
• Dorsal nerve roots


  Carry only afferent information
• Ventral nerve roots


  Carry only efferent information
• Dorsal root ganglion


  A little bulge associated with the dorsal nerve roots, contains cell bodies
• Spinal nerves


  Are both afferent and efferent
• Afferent information arrives at the dorsal nerve root via the dorsal root ganglion
• Efferent information leaves the spinal cord at the ventral nerve root
• Spinal nerves


  Are like the motorway, carrying a mix of afferent and efferent information
• Dorsal ramus (branch)


  Carries efferent information to the back, and afferent information from the back
• Ventral ramus (branch)


  Carries efferent information to the ventral body, and afferent information from the ventral body
• Rami communicans


  Communicating branches associated with the sympathetic nervous system, only present from T1 - L2
• Peripheral nerve


  Bundles of axons in the PNS
• Endoneurium


  Covers individual axons, wraps around the outside if myelinated