Answer
The first two vertebrae, C1 an C2 arte cleary atypical, even within the cervical group: the atlas (C1), is basically just a ring of bone; the axis (C2), is unique in the possession of the the vertical bony peg called the dens or odontoid process . The vertebrae C3-C6 may be considered typical cervical vertebrae, with the following distinctive features: each has a bifid (split) spinous processes, and transverse processes each with a round hole or foramen. These transverse foramina allow the passage of vertebral arteries to supply the brain, and vertebral veins that drain some structures of the neck. Cervical vertebrae are the only vertebrae with transverse foramina.
Cervical vertebrae C-7 is distinctive in its own ways: it is a very large cervical vertebra with a prominent non-bifid spinous process that can be palpated as a bump in the back of the neck. This vertebra is also called vertebra prominens. Generally, the vertebral foramen of a typical cervical vertebra is trianguloid in shape.
The thoracic vertebrae: The following are the special features of this group: heart-shaped body, intermediate in size between the smaller cervical body and the more massive lumbar vertebral body; circular vertebral foramina; a pointed spinous process that is inclined downwards and posteriorly; superior and inferior demifacets on each side of the body for articulation with the heads of ribs ; transverse processes with costal facets for articulation with shafts of ribs. There are no costal facets on ribs 11 and 12 because these ribs articulate only with bodies of vertebrae and not with transverse processes.
In vertebrae T1-T10, there are transverse costal facets at the end of each transverse process; these smooth surfaces articulate with ribs 1 through 10. Ribs 11 and 12 attach only to the bodies of vertebrae, therefore there are no transverse costal facets on T11 and T12.
Work Step by Step
The lumbar vertebrae are larger than the cervical, and the thoracic vertebrae-- they are thick with blunt rather than pointed spinous processes. The articulating surfaces of the bodies are situated differently from those of thoracic vertebrae: their superior articulating processes face medially and their inferior articulating facets face laterally-- an arrangement that promotes stability of the lower vertebral column.
