The spinal nerves exit from the vertebral column through openings between adjacent vertebrae. These openings, called intervertebral foramina, are located just in front of the facet joints. The spinal nerves are named and numbered according to the vertebral levels at which they exit. There are eight paired cervical nerves (C1-C8), twelve thoracic (T1-T12), five lumbar (L1-L5), five sacral (S1-S5), and one coccygeal (Co1).
-Although the spinal nerves correspond to their respective vertebral levels, the spinal cord itself is shorter than the vertebral column, extending only as far as the L1 vertebra. Below that level, the spinal canal contains only the roots of the lumbar, sacral, and coccygeal nerves, as they descend to exit at the appropriate levels. This bundle of descending nerve roots is called the cauda equina (Latin for "horse's tail").
The on the right views a portion of the spinal cord, showing its right lateral surface. The dura is opened and arranged to show the nerve roots.