The thoracic vertebrae (T1 - T12) form the second region of the spine, and they also participate in the formation of the posterior wall of the thorax. Like the rib pairs that are attached to them, the thoracic vertebrae are also twelve in number. These vertebrae are positioned between the cervical and lumbar vertebrae. They articulate with the ribs, and the main distinguishing feature of the thoracic vertebrae is the presence of the costal facets.