Kin 427 Week 2 Part 2

• Lumbar and sacral plexus

  • 5 pairs of mixed nerves
• Internal disc disruptions propagate outward
• Lumbar arteries

  Arise from aorta, Travel dorsally around vertebral body towards foramina
• Lumbar veins lack valves
• Intervertebral disc

  Relies on diffusion for nutrients (this is why movement is important)
• Richly Vascularized


  • Muscles, Vertebrae
• Avascular (indirectly)


  • Ligaments, tendons, articular cartilage
• Dermatome


  Area of skin supplied by a single spinal nerve
• Myotome


  Group of muscle innervated by a single nerve root
• Myotome - L4


  • Ankle dorsiflexors (e.g. tibialis anterior)
• Myotome - L5


  • 1st metatarsal (big/great toe) extension (e.g. ext. hallucis longus)
• Myotome - S1


  • Ankle plantarflexors (e.g. gastrocnemius, soleus)
• Reflex - L4


  • Knee jerk
• Reflex - L5


  • Medial hamstring
• Reflex - S1


  • Ankle jerk
• Disrupted L4/L5 disc

  May compress L5 nerve root, which could manifest as: sensory deficit/tingling – dorsum of foot and leg, motor deficit – big toe extension (± hip abduction) weakness, abnormal medial hamstring (semitendinosus) reflex, positive (painful) straight-leg test