Spine - Vertebral Column

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There are 24 articulating vertebra:

  • 7 cervical
  • 12 thoracic
  • 5 Lumbar
The sacrum and coccyx consist of fused vertebra. The sacrum consists of fused vertebra, and the coccyx consists of 3-5 fused vertebra.

In between each vertebra you have an intervertebral disc, which forms a cartilaginous joint between the vertebra. These discs function to absorb shock and to allow slight movement between the vertebrae.

The intervertebral discs consist of an outer annulus fibrosis and an inner nucleus pulposus. A slipped disc occurs when this soft jelly like substance (the nucelus pulposus) protrudes through the annulus fibrosis and irritates the surrounding spinal nerve roots.

The vertebrae are numbered

So the cervical vertebra are referred to as C1-C7, the thoracic vertebra are referred to as T1-T12, and the lumbar vertebra are referred to as L1-L5. So C1 is the most superior cervical vertebra and C7 is the most inferior cervical vertebra, and the same for the thoracic and lumbar regions.

Why is this important?

Because in anatomy and in clinical medicine the vertebral levels are used as reference points to identify where other structures lie. For instance, when performing a lumbar puncture, so as to avoid damaging the spinal cord, the needle is inserted between the lumbar vertebra L3/L4 because in adults, it is known that the spinal cord ends at around the L1/L2 vertebral level.

Spinal curvatures

  • Cervical curve
  • Thoracic curve
  • Lumbar cure
  • Pelvic curve
At birth, the spine is flexed into a single curvature - the primary curvature. The cervical and lumbar curves develop later, and are called secondary curvatures.

Spinal movements

  • Atlanto-occipital joint - flexion/extension, and slight lateral motion
  • Atlanto-axial joint - twisting left to right
  • Thoracic - rotation
  • Lumbar - flexion and extension, lateral flexion, small amount of rotation