1. Spinal cord and spinal nerves
Sanjaya Adikari
Department of Anatomy

2. Spinal cord Extends from the foreman magnum to the lower border of L1
Divided into five regions
Covered by the meninges for protection
CSF in the subarachnoid space

3. Coverings of the spinal cord

4. Spinal nerves
Spinal nerves come out through the intervertebral foramina

5. Vertebral column
Spinal cord 7 12 5 8 1

6. Spinal nerves C1 C1 C2 C3 C4 C5 C6 C7 C8 C7 C8 T1 T1 T2 T2 T3 T4 T5 T6
L1, L2
L3, L4 L5
S, C C8 T1 T2
T10

7. Cauda equina Consists of sensory and motor nerve roots below L1
These are unmixed/pure nerves
Pia mater continues below L1 as a cord named filum terminale

8. Length of the spinal cord
Black line indicates dura and arachnoid together. Pia is in blue.
T12 L1 L2 L3 L4 L5
Sacrum
Coccyx
Foetus
at 3 months
T12 L1 L2 L3 L4 L5
Sacrum
Coccyx
At birth S2
T12 L1 L2 L3 L4 L5
Sacrum
Coccyx
Adult

9. Lumbar puncture What are the risks of lumbar puncture ?
Performed to get CSF for investigation
Vertebral column is fully flexed
Needle inserted between L3 and L4 spines (or one space above)
Collects CSF from subarachnoid space
What are the risks of lumbar puncture ?

10. Cross section of spinal cord
Posterior median septum
Posterior horn
Lateral horn
Anterior horn
Anterior median fissure
Central canal
Posterior white column
Lateral white column
Anterior white column
Anterior nerve root
Posterior nerve root

11. Dorsal root ganglion
Somatic
Autonomic
sensory
motor

12. Dorsal root ganglion
Somatic
Autonomic
sensory
motor

14. Dorsal and ventral roots
Posterior roots contain afferent (sensory) axon
Anterior roots contain efferent (motor) axons
The anterior roots continue out from the spinal cord, and mix with their corresponding posterior nerve root at a point after the ganglion
Combination of the two roots is called a mixed spinal nerve.

15. Spinal nerve is mixed (motor + sensory + autonomic)
Spinal nerve refers to the mixed spinal nerve
It is formed from the dorsal and ventral roots
Passes out through the intervertebral foramen
There are 31 bilaterally-paired spinal nerves
8 cervical nerves (C1-C8)
12 thoracic nerves (T1-T12)
5 lumbar nerves (L1-L5)
5 sacral nerves (S1-S5)
1 coccygeal nerve (Co)

16. Dermatome
Area of skin supplied by a single spinal nerve or spinal cord segment
Myotome
The muscle/s supplied by a single spinal nerve or spinal cord segment

17. Nerve plexus
Is formed by nerves interlaced with numerous communicating branches
What are the advantages
of a nerve plexus?
Last’s Anatomy, 10th ed.
Page 13

18. Blood supply of spinal cord

19. Two posterior spinal arteries
Arise from PICA
Supply posterior 1/3 of spinal cord
One anterior spinal artery
Arise as two from vertebral arteries
Supply anterior 2/3 of spinal cord
Segmental spinal arteries
Enter the vertebral canal through intervertebral foramina
Divides into anterior & posterior radicular arteries. Radicular arteries accompany nerve roots

21. Ant/post spinal arteries become very small at thoracic region and the segmental spinal arteries and additional feeder arteries compensate for the deficiency

22. Great anterior medullary artery of Adamkiewicz

23. Venous drainage is into internal vertebral venous plexus