The thoracic region typically consists of 12 vertebrae. T2 – T9 share a “typical” thoracic pattern while the other thoracic vertebrae display variations on this pattern.
T1 differs from the typical pattern in its costal articulations. It is the only vertebra to articulation with the first rib, so it has a large, full facet on the superior border of the body. Inferiorly, it has a typical demifacet. The outline of its body is more similar to a cervical vertebra than a typical heart-shaped thoracic. The transverse processes project more laterally, and less dorsally than the processes of typical thoracic vertebrae.