ribs

12 pairs of thin, slightly twisted and curved BONES that form the thoracic rib cage,which protects the LUNGS and HEART . The ribs are the first seven pairs, which are each connected to the STERNUM at the front by a COSTAL CARTILAGE . The false ribs are the next three pairs and are indirectly connected to the sternum as each is attached by its cartilage to the rib above. The floating ribs are the last two pairs, which are unattached and end freely in the muscle of the thoracic wall. At the backbone, the head of each rib articulates with one of the 12 thoracic VERTEBRAE .