Rib
Ribs are classed as flat bones which usually have a protective role in the body. Humans have 24 ribs, in 12 pairs. All are attached at the back to the thoracic vertebrae, and are numbered from 1–12 according to the vertebrae they attach to. The first rib is attached to thoracic vertebra 1 (T1). At the front of the body most of the ribs are joined by costal cartilages to the sternum. The ribs connect to the vertebrae with two joints, the costovertebral joints.
Pump handle movement
One of the most important functions of the ribs and diaphragm is the change in volume of the thorax that helps inspiration and expiration. In general, the ribs move around two axes. The anterior end of the rib is lower than the posterior end; therefore, during elevation of the rib, the anterior end also moves forwards. Movement at costovertebral joints 2 to 6 about a side-to-side axis results in raising and lowering the sternal end of the rib, the "pump-handle" movement.This occurs mostly in the vertebrosternal ribs. In elevation, this increases the anteroposterior diameter of the thorax.