Which of these statements is correct when outward airflow has ceased at the end of a normal expiration?
A)Intra-alveolar pressure is less than atmospheric pressure.
B)Intra-alveolar pressure is greater than atmospheric pressure.
C) Intra-alveolar pressure is equal to atmospheric pressure.
D) Intrapleural pressure is greater than atmospheric pressure.

Question

Quizplus · Accepted Answer

At the end of a normal expiration, the muscles of respiration have relaxed and the diaphragm has returned to its resting position. This causes a decrease in thoracic volume and an increase in intra-alveolar pressure. However, since there is no more airflow, the pressure inside the lungs will eventually equalize with the atmospheric pressure, which is considered to be at 0 cm H2O. Therefore, intra-alveolar pressure is equal to atmospheric pressure at the end of a normal expiration. Intrapleural pressure may be lower than atmospheric pressure, but this is not asked in the question.

Which of These Statements Is Correct When Outward Airflow Has