The spine has three main sections, cervical, thoracic, and lumbar. There are seven cervical vertebrae (C1-C7), twelve thoracic (T1-T12), and five lumbar (L1-L5). In addition, there are two fused vertebrae, the sacrum and the coccyx.
The twelve thoracic and five lumbar vertebrae make up the thoracolumbar spine. The cervical spine supports the head and allows anterior, posterior, and lateral flexion and extension, plus rotation of the head and neck. C2, called the axis, forms a pivot with C1, called the atlas, around which the head rotates on the cervical spine. Normal curvature is lordotic (eyes pointing up).
The thoracolumbar spine (T1-L5) has two normal curvatures, lordotic in the lumbar region and kyphotic in the thoracic region. The primary spinal functions are to maintain an erect posture, provide stability and mobility, transmit loads, absorb shocks, and protect the spinal cord.