Question

Which of these statements is incorrect regarding the mechanism of breathing?

• A. On an average, a healthy human breathes around 12-16 times/min.
• B. The contraction of external intercostal muscles lifts up the ribs and the sternum causing a decrease in the volume of the thoracic chamber.
• C. Inspiration is initiated by the contraction of diaphragm, which increases the volume of thoracic chamber.
• D. Creating a pressure gradient between the lungs and the atmosphere carries out the movement of air into and out of the lungs.

Answer 1

The correct option is D

Creating a pressure gradient between the lungs and the atmosphere carries out the movement of air into and out of the lungs.

The lung pressure is always equal to the atmospheric pressure in its resting state. This is why when a person is stabbed in the chest they often suffer from lung collapse. This is because atmospheric air rushes in and equalises the intra pleural pressure with the atmospheric pressure. Without the negative pressure pulling on the lungs, they collapse.