What physiological capability does elastic recoil determine?

• A. Vital capacity
• B. Functional capacity
• C. Inspiratory reserve volume
• D. Expiratory reserve volume

Answer: (B)

Elastic recoil refers to the ability of the lungs and chest wall to return to their original shape after being stretched or expanded during inhalation. This capacity is crucial in the process of ventilation because it plays a significant role in how easily the lungs can expel air during exhalation.

Functional capacity specifically refers to the volume of air remaining in the lungs after a normal tidal expiration. It reflects the balance between the elastic recoil of the lungs and the forces that promote lung expansion. If the elastic recoil is strong, the lungs can efficiently expel the maximum amount of air during a normal breath cycle, contributing to optimal functional capacity.

In contrast, vital capacity measures the maximum amount of air that can be exhaled after a maximum inhalation, while inspiratory and expiratory reserve volumes are specific capacities that represent additional air that can be inhaled or exhaled beyond tidal volume. While elastic recoil may influence these volumes to some extent, it is the functional capacity that most directly relates to the ability of the lungs to maintain appropriate pressure and volume dynamics during normal breathing.