In order to inspire to a lung volume greater than approximately 70% of TLC, the inspiratory mus-cles must overcome:

a. the recoil of the lungs.
b. the recoil of both the lungs and the chest wall.
c. the recoil of both the chest walls.
d. the recoil of the alveoli.

ANS: B
At the beginning of the breath, the tendency of the chest wall to expand facilitates lung expan-sion. When lung volume nears 70% of the VC, the chest wall reaches its natural resting level. In order to inspire to a lung volume greater than approximately 70% of TLC, the inspiratory muscles must overcome the recoil of both the lungs and the chest wall (see Figure 11-7).