The rib cage is a bony structure that protects the heart and other organs in the chest. It is made up of 24 ribs, 12 on each side, that are attached to the sternum, or breastbone, by cartilage. The first seven pairs of ribs are called true ribs because they are attached to the sternum directly by cartilage. The next five pairs of ribs are called false ribs because they are attached to the sternum indirectly by cartilage. The last two pairs of ribs are called floating ribs because they are not attached to the sternum at all.