SPINAL CORD
- Length : 45 cm, occupying the 2/3 of the vertebral canal.
- Cylindrical in shape.
- Begins : at the upper border of atlas vertebra as the continuation of the medulla oblongata, from foramen magnum.
- Ends : at the level of L1-L2 in adults. In infant, it reaches the level of L3.
- Its lower end called "conus medullaris" from the apex of conus medullaris a pia matter filaments "filum terminale" extends downwards to be attached to the back of the coccyx.
filled with cerebrospinal fluid.
Enlargments :
because there is more gray matter in the anterior grey horn "Particulary lateral region"
- Have 2 enlargments :
- 1) Cervical enlargment : giving the roots of the brachial plexus. (C5 - T1)
- 2) Lumbar enlargment : giving the roots of the lumbar and sacral plexus. (L2-S3)
Exit of spinal nerves from the vertebral canal :
- C1-C7: above the corresponding vertebra.
- C8: below C7 vertebra.
- T1-L5: below corresponding vertebra.
- S1-S4: anterior and posterior sacral foramina.
- S5 and Co: from the sacral hiatus.
- So, the collection of nerves that will surround the filum terminale below the level of L2 vertebra resembling a horse tail is called "the cauda equina". It occupies the lower 1/3 of the vertebral canal and the whole sacral canal.
- To calculate the vertebral level:
- In cervical region: vertebral level = spinal segment – 1
- In upper thoracic region (T1-T6): vertebral level = spinal segment – 2
- In lower thoracic region (T7-T12): vertebral level = spinal segment – 3
- In lumbar region: vertebral level = spinal segment – 4
- All sacral segments + coccygeal segment are at the level of L1-L2 vertebra.