Gross Anatomy of the Spinal Cord and Spinal Nerves

Introduction

• The spinal cord and brain are components of the Central Nervous System (CNS).
• Peripheral Nervous System (PNS) includes spinal nerves, having sensory and motor components (somatic and visceral).
• Spinal cord and spinal nerves are intimately connected.

Basic Anatomy of the Spinal Cord

• Start and End Points:
  • Begins at C1 (first cervical vertebrae) right below the foramen magnum.
  • Ends around L1-L2 vertebrae.
• Segmental Division:
  • Segments: Cervical, Thoracic, Lumbar, Sacral, Coccygeal.
  • Names correspond to vertebral regions.

Spinal Cord Segments

• Cervical Segment
• Thoracic Segment
• Lumbar Segment
• Sacral Segment
• Coccygeal Segment

Spinal Nerves

• Part of the Peripheral Nervous System.
• Number of Spinal Nerves:
  • Cervical: 8 pairs
  • Thoracic: 12 pairs
  • Lumbar: 5 pairs
  • Sacral: 5 pairs
  • Coccygeal: 1 pair
  • Total: 31 pairs
• Positioning:
  • Cervical nerves exit above corresponding vertebrae; others exit below.

Key Anatomical Features

• Conus Medullaris: End of the spinal cord (L1-L2).
• Cauda Equina: Bundle of nerves from L2 to Coccygeal 1.
• Cervical Enlargement: C5 to T1, associated with upper limb muscles.
• Lumbar Enlargement: L2 to S3, associated with lower limb muscles.

Cross-Sectional Anatomy

• White Matter:
  • Carries ascending (sensory) and descending (motor) information.
  • Decreases from cervical to coccygeal segments.
• Gray Matter:
  • Houses cell bodies of neurons.
  • Increases from cervical to coccygeal segments.

Spinal Cord Cross-Section

• Gray Matter:
  • Posterior Gray Horn: Sensory neurons.
  • Anterior/Ventral Gray Horn: Motor neurons (somatic).
  • Lateral Gray Horn (T1-L2): Preganglionic motor neurons of the sympathetic nervous system.
• White Matter:
  • Ascending sensory and descending motor tracts.

Anatomy of the Spinal Nerve

• Roots:
  • Dorsal Root: Sensory pathways, contains Dorsal Root Ganglion.
  • Ventral Root: Motor pathways.
• Rami:
  • Dorsal Rami: Supplies back and neck muscles and skin.
  • Ventral Rami: Supplies anterior trunk and limbs.

Function of Spinal Nerves

• Contains mixed sensory and motor fibers.
• Sensory Pathway:
  • Sensory info enters via dorsal/ventral rami, through spinal nerve and dorsal root.
  • Synapses in dorsal gray horn, activates interneurons.
• Motor Pathway:
  • Motor info travels from ventral gray horn through ventral root and spinal nerve.

Conclusion

• Detailed overview of the spinal cord and spinal nerves.
• Emphasis on understanding the connections and functional anatomy.

Additional Resources

• Encouragement to explore external resources for further learning (e.g., Facebook, Instagram, Patreon).