Spinal Cord

SPINAL CORD

I. INTRODUCTION:
    • It is derived from the caudal part of the neural tube.
    • It is surrounded by three membranes, the meninges—the outer dura mater, the middle arachnoid mater and the inner pia mater.

II. EXTERNAL MORPHOLOGY:
A. LOCATION OF SPINAL CORD
    • It extends in adults, from the foramen magnum to the lower border of the L1 vertebra.
    • In newborns, it extends to the L3 vertebra.
    • It is continuous with the medulla oblongata at the spinomedullary junction, a plane which is marked by three structures:
              1. the forman magnum,
              2. the pyramidal decussation, and
              3. the emergence of the first cervical nerve.

B. RELATIONSHIP OF SPINAL CORD SEGMENTS WITH VERTEBRAL NUMBERS:

    • Because the spinal cord is shorter than the vertebral column, the spinal cord segments do not correspond numerically with the vertebrae that lie at the same level
    • The following table will help determine which spinal segment is related to a given vertebral body:
VERTEBRAE SPINAL SEGMENT
    • Cervical vertebrae Cervical nerves +1 (C1-C8 & T1)
    • T1-T6 vertebrae Upto T6 nerve   +2 (T2-T8)
    • T7-T9 vertebrae Upto T9 nerve   +3 (T9-T12)
    • T10 vertebra L1 & L2 nerves
    • T11 vertebra L3 & L4 nerves
    • T12 vertebra L5 nerve
    • L1 vertebra All remaining nerves (S1-S5 & Co)

C. ATTACHMENTS OF SPINAL CORD
1. LIGAMENTUM DENTICULATUM
    • These are two flattended bands of pia mater that attach to the dura mater with about 20 teeth.
2. FILUM TERMINALE
    • It is a vertical filament of pia mater extending from the conus medullaris to the back surface of vertebral foramen of coccyx, with which it fuses.
3. SPINAL NERVE ROOTS
    • Along the entire length of the spinal cord are attached 31 pairs of spinal nerves by the anterior or motor roots and posterior or sensory roots.
    • Each posterior root possesses a posterior root ganglion that is located in the...