Bone · Chest

Twelfth rib

The shortest rib, and in some people shorter than the first. It floats free at the front, has no tubercle, no angle and usually no costal groove, and its head carries a single facet for the twelfth thoracic vertebra. Quadratus lumborum attaches along much of its lower border and the most lateral fibres of the diaphragm arise from its inner surface, so this small bone is where the back of the abdominal wall and the back of the diaphragm meet.