<P> The atlas differs from the other vertebrae in that it has no body and no spinous process . It has instead a ring - like form, having an anterior and a posterior arch and two lateral masses . At the outside centre points of both arches there is a tubercle; an anterior tubercle and a posterior tubercle for the attachment of muscles . The front surface of the anterior arch is convex and its anterior tubercle gives attachment to the longus colli muscle . The posterior tubercle is a rudimentary spinous process and gives attachment to the rectus capitis posterior minor muscle . The spinous process is small so as not to interfere with the movement between the atlas and the skull . On the under surface is a facet for articulation with the dens of the axis . </P> <P> Specific to the cervical vertebra is the transverse foramen (also known as foramen transversarium). This is an opening on each of the transverse processes which gives passage to the vertebral artery and vein and a sympathetic nerve plexus . On the cervical vertebrae other than the atlas, the anterior and posterior tubercles are on either side of the transverse foramen on each transverse process . The anterior tubercle on the sixth cervical vertebra is called the carotid tubercle because it separates the carotid artery from the vertebral artery . </P> <P> There is a hook - shaped uncinate process on the side edges of the top surface of the bodies of the third to the seventh cervical vertebrae, and also of the first thoracic vertebra . Together with the vertebral disc, this uncinate process prevents a vertebra from sliding backwards off the vertebra below it and limits lateral flexion (side - bending). Luschka's joints involve the vertebral uncinate processes . </P> <P> The spinous process on C7 is distinctively long and gives the name vertebra prominens to this vertebra . Also a cervical rib can develop from C7 as an anatomical variation . </P>

What is the purpose of the vertebral body