Ventilation of the lungs involves muscles working together. Which option describes inspiration (inhalation)?
In inspiration at rest, the external intercostal muscles and the diaphragm contract, and the rib cage moves up and out.
In inspiration at rest, the internal intercostal muscles contract and the diaphragm relaxes, moving the rib cage down and in.
In forced inspiration, the external intercostal muscles relax and the internal intercostal muscles contract.
In inspiration at rest, the diaphragm relaxes and becomes dome-shaped, pulling the rib cage up and out.
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