How are ribs classified?
Three classifications of ribs exist. True ribs attach to the sternum or breastplate. These are the top seven bilaterally (on both sides). False ribs also attach to the sternum but they do so by way of costal cartilage. These are the lower ribs. There are also what is called floating ribs. Floating ribs are at the bottom of the rib cage, they do not attach to anything, they "float", they help to protect the kidneys among other structures.
The general function of all the ribs and rib cage is protecting underlying structures. True ribs serve to protect the lungs, heart, and great blood vessels. False ribs protect the lower lung fields and the liver on the right side and the spleen on the left side.