1. The Nervous System: Spinal Cord and Spinal Nerves
Chapter 14

2. Spinal Cord & Spinal Nerves
Truly the pathway between body and mind
Conducts impulses to and from the brain
Carries out spinal reflexes
Spinal nerves
31 pairs
All are mixed nerves

3. Structure of the Spinal Cord
Extends from the foramen magnum to the first or second lumbar vertebra.
Ends in the conus medullaris
Filum terminale
Extends from conus medullaris to sacral vertebrae
Cauda equina
= filum terminale + dorsal & ventral roots from spinal nerves that extend below conus medularis
Human Anatomy, 3rd edition
Prentice Hall, © 2001

4. Coverings of the Spinal Cord
3 layers called meninges
Dura mater
Outer layer
Arachnoid
Middle layer
Pia mater
Adheres tightly to the surface of the spinal cord

5. Meninges of the Spinal Cord
FG14_02.JPG
Title: The Spinal Cord and Spinal Meninges
Notes: (a) Anterior view of spinal cord showing meninges and spinal nerves. (b) MRI scan of inferior portion of spinal cord. (c) Posterior view of spinal cord; meningeal layers, superficial landmarks, distribution of gray and white matter. (d) Sectional view throu
Keywords: spinal cord, meninges, spinal nerves, anterior median fissure, pia mater, denticulate ligaments, arachnoid mater, dura mater, cervical nerve, rami communicantes, autonomic ganglion, ventral ramus
Human Anatomy, 3rd edition
Prentice Hall, © 2001

6. Meninges of the Spinal Cord
Human Anatomy, 3rd edition
Prentice Hall, © 2001

7. Sectional Anatomy of the Spinal Cord
Inner part consists of gray matter
Unmyelinated cell bodies, neuroglia, & dendrites
Organized into “horns”
Outer part consists of white matter
Tracts (columns) of myelinated fibers
Ascending tracts are sensory
Descending tracts are motor
Human Anatomy, 3rd edition
Prentice Hall, © 2001

8. Example of Ascending Nerve Tracts
Human Anatomy, 3rd edition
Prentice Hall, © 2001

9. Human Anatomy, 3rd edition
Spinal Nerves
Connect to the spinal cord via a dorsal and a ventral root
Dorsal root is sensory
Contains a dorsal root ganglion
Ventral root is motor
Human Anatomy, 3rd edition
Prentice Hall, © 2001

10. Human Anatomy, 3rd edition
Spinal Nerves
The roots unite into the spinal nerve
Spinal nerves exit through intervertebral foramen
Split into branches, or rami.
Dorsal ramus
Ventral ramus
Regions of skin supplied by a spinal nerve = dermatomes (“skin slices”)
Human Anatomy, 3rd edition
Prentice Hall, © 2001

11. Human Anatomy, 3rd edition
Dermatomes
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Title: Dermatomes
Notes: Anterior and posterior distribution of dermatomes; the related spinal nerves are indicated for each dermatome.
Keywords: dermatomes, anterior, posterior
Human Anatomy, 3rd edition
Prentice Hall, © 2001

12. Human Anatomy, 3rd edition
Nerve Plexuses
Plexus = “braid”
Nerves supplying the limbs form plexuses when they leave the spinal cord
Cervical plexus
Brachial plexus
Lumbosacral plexus
Lumbar plexus
Sacral plexus
Human Anatomy, 3rd edition
Prentice Hall, © 2001

13. Human Anatomy, 3rd edition
Cervical Plexus
Formed by spinal nerves C1 – C5
Nerves innervate the neck and shoulder region
Phrenic nerve to the diaphragm
Human Anatomy, 3rd edition
Prentice Hall, © 2001

14. Human Anatomy, 3rd edition
Brachial Plexus
Formed by spinal nerves C5 – C8 and T1
Nerves innervate the arm and shoulder
Radial nerve
Ulnar nerve
Median nerve
Human Anatomy, 3rd edition
Prentice Hall, © 2001

15. Human Anatomy, 3rd edition
Brachial Plexus
FG14_11A.JPG
Title: The Brachial Plexus
Notes: (a) The trunks and cords of the brachial plexus.
Keywords: brachial plexus, superior trunk, middle trunk, inferior trunk, medial cord, lateral cord, posterior cord, musculocutaneous, median, radial, ulnar, axillary
Human Anatomy, 3rd edition
Prentice Hall, © 2001

16. Human Anatomy, 3rd edition
Lumbosacral Plexus
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Title: The Lumbosacral Plexus, Part I
Notes: (a) Anterior view of the lumbar plexus; origins and major brances. (b) Anterior view of sacral plexus; origins and major branches. (c) Anterior view of the lumbrosacral plexus and innervation of lower limb. (d) Posterior view of sacral plexus and associat
Keywords: lumbosacral plexus, lumbar plexus, sacral plexus, lumbosacral trunk, iliohypogastric nerve, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral, obturator, tibial, peroneal, medial plantar, pudendal, gluteal, sciatic, saphenous
Human Anatomy, 3rd edition
Prentice Hall, © 2001

17. Human Anatomy, 3rd edition
Lumbar Plexus
Formed by spinal nerves T12 and L1 – L4.
Innervates the medial and anterior portions of the thigh and lower abdominal regions
Lateral femoral cutaneous nerve
Human Anatomy, 3rd edition
Prentice Hall, © 2001

18. Human Anatomy, 3rd edition
Sacral Plexus
Formed by spinal nerves L4 and L5, and S1 and S2
Innervates the posterior portion of the hip, thigh, and leg, and the genital region
Sciatic nerve
Human Anatomy, 3rd edition
Prentice Hall, © 2001

19. Human Anatomy, 3rd edition
Sacral Plexus
FG14_13B.JPG
Title: The Lumbosacral Plexus, Part I
Notes: (a) Anterior view of the lumbar plexus; origins and major brances. (b) Anterior view of sacral plexus; origins and major branches. (c) Anterior view of the lumbrosacral plexus and innervation of lower limb. (d) Posterior view of sacral plexus and associat
Keywords: lumbosacral plexus, lumbar plexus, sacral plexus, lumbosacral trunk, iliohypogastric nerve, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral, obturator, tibial, peroneal, medial plantar, pudendal, gluteal, sciatic, saphenous
Human Anatomy, 3rd edition
Prentice Hall, © 2001

20. Spinal Reflexes Reflexes are automatic responses to stimuli
Spinal reflexes result from the stimulation of a spinal reflex arc.

21. Basic Elements of a Reflex Arc
Human Anatomy, 3rd edition
Prentice Hall, © 2001

22. Spinal Cord Injuries Can affect sensory perception; motor paralysis
Location affects severity of the injury
Spinal compression results from squeezing the spinal cord within the vertebral canal
Spinal transection is the severing of the spinal cord

23. Spinal Cord Injuries Quadriplegia Paraplegia