The spine is a stack of 33 vertebrae that holds the body upright and protects the spinal cord. Discs between the vertebrae absorb shock and allow movement.
Five regions
There are 7 cervical, 12 thoracic and 5 lumbar vertebrae, followed by the sacrum (5 fused) and the coccyx (usually 4 fused). Each region has a shape suited to its job.
Normal curves
Seen from the side, the neck and lower back curve forward (lordosis) and the chest and sacrum curve backward (kyphosis). A sideways curve is called scoliosis.
Special vertebrae
C1 (atlas) holds the skull and C2 (axis) lets the head rotate. C7 has the most prominent spinous process at the base of the neck.
Discs and the cord
Each disc has a tough outer ring and a soft center that can herniate and press on a nerve root. In adults the spinal cord ends around L1 to L2; below that, only nerve roots continue.
| Region | Vertebrae | Main feature |
|---|---|---|
| Cervical | C1 to C7 | Most mobile, protects the vertebral arteries |
| Thoracic | T1 to T12 | Joins the ribs |
| Lumbar | L1 to L5 | Largest bodies, carries most weight |
| Sacrum | 5 fused | Joins the pelvis |
| Coccyx | 3 to 5 fused | Tailbone |
At the bedside
Because the cord ends near L2, a lumbar puncture is done at L3 to L4 or L4 to L5, found at the level of the tops of the iliac crests. After trauma, keep the spine aligned until injury is ruled out.
Related guides
Written by Making Synapses. Topic reference: OpenStax, Anatomy and Physiology 2e (no text adapted).