During a forced inspiration, in addition to the diaphragm, which muscles contract to raise the ribs?
- A. the abdominal muscles only
- B. the internal intercostal muscles only
- C. the external intercostal muscles
- D. the smooth muscles of the alveoli
Explanation
The external intercostals lift the rib cage up and out, enlarging the thorax with the diaphragm's downward pull. The internal intercostals and abdominal muscles act in forced expiration instead.
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