Lecture Notes: Spinal Nerves and Plexuses

Introduction to Spinal Nerves

• 31 pairs of nerves emerging from the spinal cord.
• Formation:
  • Dorsal and ventral roots merge to form a spinal nerve.
• Naming:
  • Named according to their points of issue from the vertebrae:
    • Cervical (C), Thoracic (T), Lumbar (L).
• Characteristics:
  • Mixed nerves: carry both sensory and motor functions.

Spinal Nerve Networks (Plexuses)

• Plexus definition: Network of nerves.
• Four main plexuses:
  1. Cervical Plexus
  2. Brachial Plexus
  3. Lumbar Plexus
  4. Sacral Plexus

Cervical Plexus

• Emergence: C1 to C4.
• Function:
  • Innervates muscles and skin of the neck and shoulders.
  • Includes the Phrenic nerve, critical for diaphragm function.
  • Importance: Damage can lead to paralysis and breathing issues.

Brachial Plexus

• Emergence: C5 to T1.
• Function:
  • Innervates shoulders, thorax, and upper limbs.
  • Notable nerve: Ulnar nerve (associated with the 'funny bone').

Lumbar Plexus

• Emergence: L1 to L4.
• Function:
  • Innervates anterior and medial thigh and leg.
• Specific to the front and inside of the thigh and leg.

Sacral Plexus

• Emergence: L4 from sacrum.
• Function:
  • Innervates the rest of the lower limb.
  • Notable nerve: Sciatic nerve (largest, associated with sciatica).
  • Innervation for posterior and lateral thigh, leg, and foot.

Summary

• Spinal nerves are organized into networks for efficient functionality.
• Each plexus has a specific area and function:
  • Cervical: Neck and shoulders.
  • Brachial: Upper limbs.
  • Lumbar: Anterior and medial thigh and leg.
  • Sacral: Posterior and lateral limbs.
• Importance of understanding nerve functions and the impact on movement and sensation.