The spine is formed from 33 irregular bones that give the spine four natural curves. Two concave curves (lumbar and cervical), and two convex curves (thoracic and sacral). Each region of the spine has a different number of bones.
|Region||Number of bones||Range of movement|
|Cervical||7||Contains seven irregular bones and capable of flexion, extension, lateral flexion and rotation.|
|Thoracic||12||Contains twelve irregular bones and allows flexion, extension, lateral flexion and rotation.|
|Lumbar||5||Contains five irregular bones and allows some flexion, extension, and limited lateral flexion and rotation.|
|Sacral||5||Contains five fused bones and does not move.|
|Coccyx||4||Contains four fused bones and does not move.|