Answer:
Ribs are classified based on if and how their costal cartilages attach to the sternum. True (vertebrosternal) ribs are ribs 1-7. The costal cartilage for each of these attaches directly to the sternum. False (vertebrochondral) ribs, 8-12, are attached either indirectly or not at all to the sternum. Ribs 8-10 are attached indirectly to the sternum. For these ribs, the costal cartilage of each attaches to the cartilage of the next higher rib. The last false ribs (11-12) are also called floating (vertebral) ribs, because these ribs do not attach to the sternum at all. Instead, the ribs and their small costal cartilages terminate within the muscles of the lateral abdominal wall.