The first cervical vertebra is the one that sits between the head and the rest of the spine.
The atlas does not have a vertebral body, but it does have a thick anterior (ahead) arch and a narrow posterior (back) arch, as well as two sideways masses.
The atlas is located at the top of the axis, the second cervical vertebra.
It is made up of a bony bump called the odontoid process that extends through the hole in the atlas.
This one-of-a-kind setup allows you to move your head from one side to the other.
The unique ligaments that connect these two vertebrae allow for a greater degree of rotation between them.