What does the "pump handle" movement of rib pairs 2 through 7 achieve?

a. Anchor of the upper chest for diaphrag-matic contraction
b. Diminish of the energy wasted by ineffi-cient muscular contraction
c. Increase in the anteroposterior diameter of the chest
d. Increase in the lateral dimensions of the chest

ANS: C
Ribs 2 through 7 move simultaneously about two axes (Figure 9-20). As each rib rotates about the axis of its neck, its sternal end rises and falls. This movement increases the anteroposterior thoracic diameter in what is commonly referred to as a "pump handle"-like motion.