part of part of Homo sapiens thoracic vertebra 1 zone of bone organ transverse costal facet of first thoracic vertebra 2026-03-19T00:00:00Z A zone of bone organ located on the anterior surface of the transverse process of the first thoracic vertebra, articulating with the tubercle of the first rib at the costotransverse joint. T1 has well-developed transverse processes with distinct transverse costal facets that, together with the costal facets of the body, contribute to the firm articulation supporting the first rib. David Osumi-Sutherland