1. Spinal Nerves

2. Spinal nerves 31 pairs arise from spinal cord Five groups correspond to regions of spinal cord and vertebrae –Cervical 8 pr. –Thoracic 12 pr. –Lumbar 5 pr. –Sacral 5 pr. –Coccygeal 1 pr.

3. Structure of a Nerve Bundle of axons Layers of connective tissue –Epineurium –Perineurium –Endoneurium

4. Structure of a spinal nerve Tree analogy Dorsal root & ventral root fuse lateral to dorsal root ganglion Whole nerve "trunk" lies in intervertebral foramen

5. Structure of a spinal nerve Branches Dorsal ramus Ventral ramus Communicating rami to sympathetic chain ganglion (ANS)

6. Spinal Nerve Plexuses

7. Ventral rami of spinal nerves fuse and form networks with ventral rami of other spinal nerves. –Crossing of fibers A peripheral nerve may contain axons from several spinal segments. T 2 – T 12 do not form plexuses

8. Spinal Nerve Plexuses Cervical plexus Brachial plexus Lumbar plexus Sacral plexus

9. Cervical plexus C 1 – C 4 (+ C 5 ) –cutaneous nerves, mostly sensory from skin of neck & back of head –Phrenic nerve to diaphragm Motor stimulation for breathing!

10. Brachial plexus C 5 – T 1 Complex fusion, splitting, fusion, & division into nerves Axillary Nerve –to deltoid Musculocutaneous nerve –to biceps brachii, brachialis

11. Brachial plexus Radial nerve –to triceps brachii, extensors of wrist, hand, fingers Wrist drop Median nerve –to flexors of wrist, hand, fingers –can be compressed Carpal Tunnel Syndrome Ulnar nerve –(“funny bone”) –to flexors in hand “Claw hand”

12. Lumbar plexus L 1 – L 4 (+ L 5 ) Ilioinguinal nerve –mostly sensory from skin of thigh & genitals Genitofemoral nerve –mostly sensory from scrotum, labia majora, ant. Thigh Femoral Nerve –to quadriceps, sartorius

13. Sacral plexus L 4 – S 4 Superior & inferior gluteal nerves –To gluteus muscles Sciatic nerve –To hamstrings & other posterior thigh & leg muscles Pudendal nerve –Sensory from penis, clitoris, labia minora, anus