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Anatomy of the Spinal Cord Overview

Mar 16, 2025

Lecture Notes: Anatomy of the Spinal Cord

Protective Structures of the Spinal Cord

  • Spinal Cord Overview:

    • Bundle of nerves suspended in cerebrospinal fluid for protection and nourishment.
    • Protected by meninges and vertebral bodies.
  • Vertebral Canal:

    • Created by stacking vertebrae; forms a tunnel for the spinal cord.
    • Intervertebral foramina allow spinal nerves to enter and exit.
  • Meninges:

    • Continuous with cranial meninges.
    • Consist of dura mater, arachnoid mater, and pia mater.
    • Cerebrospinal fluid circulates between pia mater and arachnoid mater.
    • Epidural space: Cushion of fat and connective tissue.

External Anatomy of the Spinal Cord

  • Extension:

    • Extends from the medulla oblongata to the inferior border of the second lumbar vertebra.
    • In adults, does not extend the full length of the vertebral column.
  • Shape and Size:

    • Oval shape, maximum diameter about 1.5 cm.
    • Thinner in thoracic region.
  • Enlargements:

    • Cervical Enlargement:
      • In the lower neck region.
      • Nerves to/from upper limbs arise here.
    • Lumbar Enlargement:
      • Located around the lower three ribs.
      • Nerves to/from lower limbs arise here.

Internal Anatomy of the Spinal Cord

  • Transverse Section:
    • White matter surrounds a butterfly-shaped gray matter core.
    • Gray Matter:
      • Contains neuron cell bodies, dendrites, axon terminals, and neuroglia.
      • Divided into horns:
        • Posterior (Dorsal) Horn: Interneurons and sensory neurons.
        • Anterior (Ventral) Gray Horn: Somatic motor neurons.
        • Lateral Gray Horn: Autonomic motor neurons (thoracic and upper lumbar regions).
    • White Matter:
      • Divided into columns:
        • Anterior (Ventral) Column
        • Posterior (Dorsal) Column
        • Lateral Columns
      • Contains tracts for ascending sensory and descending motor signals.

Spinal Nerves

  • Spinal Nerves Overview:

    • 31 pairs emerge from the spinal cord through intervertebral foramina.
    • Connect spinal cord to the body via roots and rootlets:
      • Posterior (Dorsal) Root and Rootlets:
        • Contain sensory axons.
        • Swelling at posterior root houses sensory neuron cell bodies (posterior root ganglion).
      • Anterior (Ventral) Root and Rootlets:
        • Contain motor axons.
        • Conduct signals from CNS to muscles and glands.
  • Identification Tip:

    • Posterior root ganglion helps identify dorsal side of the spinal cord.

Key Terms

  • Vertebral Foramen: Hole in vertebra for spinal cord.
  • Intervertebral Foramina: Holes for spinal nerve exit.
  • Cervical/Lumbar Enlargement: Thickenings in spinal cord for limb nerves.
  • Gray Horns: Regions in gray matter for specific neuron types.
  • White Columns: Regions in white matter for axon tracts.
  • Spinal Nerve: Mixed nerve for communication between spinal cord and body.
  • Roots and Rootlets: Connection points for spinal nerves, separating sensory and motor functions.