1. Spinal Nerves Part of PNS
Parallel bundles of axons & neuroglia wrapped in CT
Connect CNS to peripheral receptors and effectors
31 pairs
Anterior and posterior roots

2. Spinal Nerves
8 cervical nerves but only 7 vertebrae  exit above vertebrae
C8 below C7 vertebrae
Rest of nerves emerge below vertebrae with same name

3. CT Covering of Spinal Nerves
Transverse
plane
Spinal nerve
EPINEURIUM around entire nerve
Compare to endomysium, perimysium, epimysium
Fascicle
PERINEURIUM around each fascicle
Myelin sheath
Blood vessels
Axon
ENDONEURIUM around
each axon
(a) Transverse section showing the coverings of a spinal nerve

4. Branches of a Spinal Nerve
View
POSTERIOR
Spinous process of vertebra
Deep muscles of back
Transverse
plane
Spinal cord
Posterior (dorsal) root
POSTERIOR (DORSAL) RAMUS
Posterior (dorsal) root ganglion
ANTERIOR (VENTRAL) RAMUS
Anterior (ventral) root
MENINGEAL BRANCH
RAMI COMMUNICANTES
Denticulate ligament
Dura mater and arachnoid mater
Subarachnoid space
(contains CSF)
Sympathetic ganglion on sympathetic trunk
Body of vertebra
Epidural space
(contains fat and blood vessels)
ANTERIOR
Figure 13.6 (a) Superior view
Branches of a Spinal Nerve
Posterior Rami Anterior Rami Meningeal Branch Rami communicantes

5. Plexuses
Axons of anterior rami of spinal nerves form networks = plexus
Anterior rami of T2-T12  intercostal nerves  no plexus

6. Cervical Plexus

7. Brachial Plexus

8. Brachial Plexus

9. (a) Origin of lumbar plexus
From T12 L1
Iliohypogastric L2
Ilioinguinal L3
Genitofemoral
Lateral cutaneous nerve
of thigh L4
Femoral L5
Lumbar plexus
Accessory obturator (present in only about 10% of population)
Roots
Anterior division
Posterior division
Lumbosacral
trunk
Obturator
(a) Origin of lumbar plexus

10. Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Lumbar Plexus
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.

11. Sacral Plexus L4 contribution to femoral nerve L4 Lumbosacral trunk L5
Superior gluteal S2
Inferior gluteal S3
Nerve to piriformis S4
Tibial S5
Common
fibular
Coccygeal nerve
Sacral and coccygeal plexuses
Anococcygeal nerve
Sciatic
Pudendal
Nerve to quadratus femoris
and inferior gemellus
Perforating cutaneous
Nerve to obturator internus
and superior gemellus
Posterior cutaneous nerve of thigh
Roots
Anterior division
Posterior division
Origin of sacral plexus

12. Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Sacral Plexus
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.

13. Dermatomes
Certain segments of the skin are supplied by spinal nerves that carry somatic sensory nerve impulses to the brain.