Which of the following muscles contract during normal expiration?
Which of the following muscles contract during normal expiration?
The correct option is D None of these
During normal inspiration, the diaphragm and the external intercostal muscles contract. The diaphragm moves downwards increasing the volume of the thoracic (chest) cavity, and the intercostal muscles pull the ribs up expanding the rib cage and further increasing its volume. An increase in pulmonary volume decreases the intrapulmonary pressure to less than the atmospheric pressure. This forces the air from outside to move into the lungs, a process called inspiration. Relaxation of the diaphragm and the intercostal muscles returns the diaphragm and sternum to their normal positions and reduce the thoracic volume and thereby the pulmonary volume. This leads to an increase in intrapulmonary pressure to slightly above the atmospheric pressure causing the expulsion of air from the lungs, a process called expiration. Internal intercostal muscles play a role only in forced exhalation. The question here is about normal expiration and hence, the answer is D.
None of these
During normal inspiration, the diaphragm and the external intercostal muscles contract. The diaphragm moves downwards increasing the volume of the thoracic (chest) cavity, and the intercostal muscles pull the ribs up expanding the rib cage and further increasing its volume. An increase in pulmonary volume decreases the intrapulmonary pressure to less than the atmospheric pressure. This forces the air from outside to move into the lungs, a process called inspiration. Relaxation of the diaphragm and the intercostal muscles returns the diaphragm and sternum to their normal positions and reduce the thoracic volume and thereby the pulmonary volume. This leads to an increase in intrapulmonary pressure to slightly above the atmospheric pressure causing the expulsion of air from the lungs, a process called expiration. Internal intercostal muscles play a role only in forced exhalation. The question here is about normal expiration and hence, the answer is D.
