Which of the following does not occur during expiration when a person is breathing quietly?
A) The size of the thoracic cavity is reduced.
B) The intra-alveolar pressure becomes greater than atmospheric pressure.
C) Air flows out of the lungs.
D) The expiratory muscles contract.
E) Intrapleural pressure is less than intra-alveolar pressure.

Question

Quizplus · Accepted Answer

During quiet expiration, the expiratory muscles (such as the abdominal muscles) do not contract. Instead, the process is primarily passive as the elastic recoil of the lungs and chest wall allows air to flow out of the lungs. Therefore, choice D (the expiratory muscles contract) is the option that does not occur during quiet expiration. Choices A, B, and C are all accurate and describe the normal physiology of quiet expiration, while choice E would be true if discussing the pressure differences during inspiration.

Which of the Following Does Not Occur During Expiration When