The upper seven pairs of ribs are true ribs. These ribs attach directly to the sternum by a strip of hyaline cartilage called costal cartilage. The lower five pairs of ribs are known as false ribs because they either attach indirectly to the sternum or do not attach to the sternum at all. The eighth, ninth, and tenth pairs of ribs attach to each other and then to the cartilage of the seventh pair of ribs. The eleventh and twelfth pairs of ribs are floating ribs because they only attach to the vertebral column and do not attach to the sternum at all.