The human spinal column has seven vertebrae that together are known as the cervical spine. Starting at the base of the skull and moving down, the vertebrae are labeled as C1 through C7, with the C standing for cervical.
The C1 vertebra is closest to the skull and is also known as the atlas. The C2 vertebra is just below the atlas and is called the axis. The atlas is a ring-shaped vertebra that rotates around the body of the axis. This pair of vertebrae allows rotation of the neck. Forward and backward movements of the head are mainly controlled by the C5, C6 and C7 vertebrae.