1. Chapter 13: The Spinal Cord and Spinal Nerves
BIO 210 Lab
Instructor: Dr. Rebecca Clarke

2. Spinal Cord Structurally and functionally integrated with brain
Occupies upper two-thirds of vertebral column (adult: 1.5 ft long, 0.5 in. wide)
Ends between vertebrae L1 and L2

3. Gross Anatomy of the Spinal Cord
Divided into 4 regions (like vertebrae):
Cervical (C)
Thoracic (T)
Lumbar (L)
Sacral (S)
31 Pairs of spinal nerves
Named for regions
Cervical numbered for vertebra below
Rest numbered for vertebra above
Figure 13-2

4. Gross Anatomy of the Spinal Cord: Distal End
Conus medullaris (medullary cone):
Conical structure at T-L junction
Filum terminale (terminal filum):
Thin strand of fibrous tissue at end of conus medullaris
Cauda equina (“horse tail”):
Bundle of elongated nerve roots extending below conus medullaris (L2-S5)
Note: After age 4, vertebral column continues to elongate but spinal cord does not therefore roots elongate)
Figure 13-2

5. Sectional Anatomy of the Spinal Cord
Posterior median sulcus: Groove on posterior side
Anterior median fissure: Deeper, wider groove on anterior side
Gray matter covered by thick layer of white matter
Figure 13–5a

6. Sectional Anatomy of the Spinal Cord: Gray Matter
Neuron cell bodies, neuroglia, unmyelinated axons
H- or butterfly-shape with horns (projections)
Gray commissure – where axons connect R/L sides
Central canal in middle; contains CSF
Figure 13–5a

7. Sectional Anatomy of the Spinal Cord: Gray Matter
Cell bodies organized in nuclei in horns of gray matter:
Somatic and visceral
Sensory (dorsal) and motor (ventral)
Figure 13–5a

8. Sectional Anatomy of the Spinal Cord: White Matter
Spinal tracts (bundles of myelinated axons) arranged in columns
Have similar distribution as nuclei in gray matter
Relay same type of info (sensory or motor) in same direction (ascending or descending) to brain
Figure 13–5a

9. Gross Anatomy of a Spinal Nerve
Forms 2 branches on each side of spinal cord:
Dorsal root:
Contains axons of sensory (afferent) neurons coming from receptors
Ventral root:
Contains axons of motor (efferent) neurons going to effectors
Dorsal root ganglion:
Contains cell bodies of sensory neurons
Figure 13-2

10. Mixed Nerves Carry both sensory (afferent) and motor (efferent) fibers
Spinal nerves are mixed nerves

11. Spinal Nerves and Plexuses

12. Spinal Nerves and Plexuses

13. Nerve Plexus
Complex interwoven network of nerve fibers of adjacent spinal nerves
Formed during development
Nerves arising at a plexus:
Are mixed nerves (like spinal nerves)
Control skeletal muscles of neck, upper torso, limbs

14. 4 Major Nerve Plexuses Cervical plexus Brachial Lumbar Sacral
 Neck, thoracic cavity, diaphragm
 Phrenic nerve
Brachial
 Shoulder/pectoral girdle and upper limbs
 Radial and ulnar nerves
Lumbar
 Pelvic girdle and lower limbs
 Femoral nerve
Sacral
 Sciatic nerve
Figure 13–9

15. Brachial Plexus

16. Meninges Specialized, protective membranes
Separate, isolate, protect soft tissue of:
Spinal cord from bones of vertebra (spinal meninges)
Brain from bones of skull (cranial meninges)
Spinal meninges continuous with cranial meninges
Have 3 layers:
Dura (“hard”) mater – outermost covering
Arachnoid mater – middle layer
Pia (“delicate”) mater – innermost layer

17. Gross Anatomy of Spinal Cord and Meninges
Spinal cord located in vertebral foramen
Epidural space
Between vertebra and dura mater
Contains loose connective tissue, blood vessels, adipose tissue
Epidural block
Injection of anesthetic
Used to control pain
Figure 13–3

18. Gross Anatomy of Spinal Cord and Meninges
Dura mater
Arachnoid mater
Subarachnoid space
Between arachnoid membrane and pia mater
Filled with CSF
Acts as shock absorber
Carries dissolved gases, nutrients, chemical messengers, waste products
Spinal tap
Withdrawal of CSF for diagnostic purposes when CNS infection suspected, for back pain, headaches, disc problems, etc.
Pia mater
Figure 13–3

19. Meningitis
Meningitis:
Viral or bacterial infection of meninges

20. Sympathetic Chain Ganglia
String of ganglia alongside spinal cord
Figure 16–5

21. Sympathetic Chain Ganglia
Figure 16–4a