When the Muscles of Respiration Relax

Question

When the muscles of respiration relax,
A) thoracic volume decreases and air moves out of the lungs.
B) thoracic volume increases and air moves out of the lung.
C) thoracic volume decreases and air moves into the lungs.
D) thoracic volume decreases and intrapulmonic pressure decreases.

Accepted Answer

When the muscles of respiration relax, the thoracic volume decreases due to the elastic recoil of the lungs and chest wall, and this decrease in volume causes air to move out of the lungs. Therefore, the option A is the best choice.