part of part of Homo sapiens rib 12 zone of bone organ sternal end of twelfth rib 2026-03-19T00:00:00Z A zone of bone organ forming the pointed free anterior extremity of the twelfth rib that terminates in a small cartilaginous tip. As the lowest floating rib, the twelfth rib does not connect to the sternum or costal arch, and its sternal end lies within the posterior abdominal wall musculature posterior to the kidney. David Osumi-Sutherland