Which of These Actions Brings on Normal Expirations

Question

Which of these actions brings on normal expirations
A)contraction of the external intercostals
B)contraction of the internal intercostals
C)contraction of the diaphragm
D)elastic recoil of stretched lung tissues and relaxation of inspiratory muscles

Accepted Answer

Normal expirations are a passive process that occurs due to the elastic recoil of stretched lung tissues and the relaxation of inspiratory muscles. The contraction of external intercostals and diaphragm are involved in the active process of inhalation, while the contraction of internal intercostals is involved in forced expiration.