1. SPINAL CORD, SPINAL NERVE and SPINAL PLEXUSES

2. Continuation of the medulla oblangata (bulbus), the caudal part of the brain stem.
42-45 cm long
Foramen magnum-L2 (L1-L3)
Medullary cone
2 enlargements: cervical, lumbosacral

3. 33 segments, 31 paired spinal nerves
8 cervical
12 thoracic
5 lumbar
5 sacralis
3 cocygeal (1 pair of spinal nerve)
1st cervical spinal nerve: between atlas and occipital bone
8th cervical cervical spinal nerve: between C7-T1
1st thoracic spinal nerve : betwen T1-T2

4. Distal End Conus medullaris: Cauda equina: Filum terminale:
thin, conical end of the spinal cord
Cauda equina:
nerve roots extending below conus medullaris
Filum terminale:
thin thread of fibrous tissue at end of conus medullaris
attaches to coccygeal ligament

5. Spinal Meninges
Specialized membranes isolate spinal cord from surroundings
protect spinal cord
carry blood supply
continuous with cranial meninges
Pia mater-arachnoid mater –dura mater

6. Spinal Dura Mater tough and fibrous Cranially:
fuses with periosteum of occipital bone
continuous with cranial dura mater
Caudally:
tapers to dense cord of collagen fibers
joins filum terminale in coccygeal ligament (for longitudinal stability)

7. The Epidural Space
Between spinal dura mater and walls of vertebral canal (above the dura)
No such space in the brain
Contains loose connective and adipose tissue
Anesthetic injection site

8. Inter-Layer Spaces – just like in the brain
Subdural space:
between arachnoid mater and dura mater
Subarachnoid space:
between arachnoid mater and pia mater
filled with cerebrospinal fluid (CSF)
Spinal Tap withdraws CSF from inferior lumbar region (below conus medularis) for diagnostic purposes.
Where do they get the CSF?

9. Roots 2 branches of spinal nerves: Dorsal root ganglia: ventral root:
contains axons of motor neurons
dorsal root:
contains axons of sensory neurons
Dorsal root ganglia:
contain cell bodies of sensory neurons
Pseudounipolar neurons

10. White Matter fiber tracts for transmission of information
ascending (sensory) tracts
descending (motor) tracts
Posterior funiculus
Lateral funiculus
Anterior funiculus

11. Some fiber tracts in the different funiculi
Posterior funiculus:
Faciculus cuneatus and gracilis
Ascending sensory
Lateral funiculus
Spinothalamic tract
Corticospinal tract
Descending motor
Anterior funiculus

12. Reflex Arc 1) Receptor - reacts to stimulus
2) Sensory Neurons - afferent impulses to CNS
3) Integration centers - synapses in CNS
4) Motor Neurons - efferent impulses from Integration centers to effector
5) Effector - muscle or glands

13. Spinal Cord Trauma: Transection
Cross sectioning of the spinal cord at any level results in total motor and sensory loss in regions inferior to the cut
Paraplegia – transection between T1 and L1
Quadriplegia – transection in the cervical region; how high determines the extent of the damage