In
vertebrates,
thoracic vertebrae compose the middle segment of the
vertebral column, between the
cervical vertebrae and the
lumbar vertebrae. In humans, there are twelve thoracic vertebrae and they are intermediate in size between the cervical and lumbar vertebrae; they increase in size going towards the lumbar vertebrae, with the lower ones being a lot larger than the upper. They are distinguished by the presence of
facets on the sides of the bodies for
articulation with the
heads of the ribs, and facets on the
transverse processes of all, except the eleventh and twelfth, for articulation with the
tubercles of the ribs. By convention, the human thoracic vertebrae are numbered T1-T12, with the first one (T1) located closest to the skull and the others going down the spine towards the lumbar region.