Definition of Rib

Rib: One of the 12 paired arches of bone which form the skeletal structure of the chest wall (the rib cage). The ribs attach to the building blocks of the spine (vertebrae) in the back. The 12 pairs of ribs consist of: True ribs: The first seven ribs attach to the sternum (the breast bone) in the front and are known as true ribs (or sternal ribs). False ribs: The lower five ribs do not directly connect to the sternum and are known as false ribs.

The upper three false ribs connect to the costal cartilages of the ribs just above them. The last two false ribs, however, usually have no ventral attachment (no anchor at all in front) and are called floating, fluctuating or vertebral ribs.