regional_part_of Back Subdivision of trunk Back of trunk Dorsum of trunk FMA:25056 Subdivision of trunk which is demarcated from the trunk proper by the external surface of the posterolateral part of the rib cage, the anterior surface of the thoracic vertebral column and the posterior axillary lines, the external surface of the posterior abdominal wall; together with the trunk proper, it constitutes the trunk. Examples: There is only one trunk proper. Trunk back fma