What are the last two ribs that are not attached to the sternum termed?

The last two ribs that are not attached to the sternum are termed floating ribs. These special ribs are the eleventh and twelfth pairs of ribs and differ from true and false ribs in their anatomical configuration. True ribs, which are the first seven pairs, attach directly to the sternum via costal cartilage, whereas the false ribs, which include the next three pairs (eighth to tenth), attach indirectly to the sternum through the cartilage of the rib above them.

Floating ribs do not connect at all to the sternum or to any other ribs in front. Instead, they are only attached at the back to the vertebrae, making them unique in their lack of anterior articulation. This lack of connection allows for greater mobility in the torso and expansion of the diaphragm during breathing. This understanding emphasizes the structural distinction and functional role of floating ribs as compared to the other types of ribs.