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.