During inspiration the diaphragm
Correct answer: A. contracts and flattens, increasing the volume of the thorax
- A. contracts and flattens, increasing the volume of the thorax
- B. relaxes and domes upwards, increasing the volume of the thorax
- C. contracts and domes upwards, decreasing the volume of the thorax
- D. does not move at all
Explanation
A flattening diaphragm and the external intercostals swinging the ribs up and out together enlarge the thoracic cavity, so the pressure inside the lungs falls below atmospheric and air flows in. The diaphragm is a muscle, so contraction shortens and flattens the dome rather than raising it. Air movement is always the result of a pressure difference created by these volume changes.
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About Human Respiratory System
The human respiratory system conducts air to the alveoli, where oxygen and carbon dioxide exchange occurs across thin respiratory surfaces. Questions cover the nasal passage, trachea, bronchi, lungs, diaphragm and intercostal muscles, ventilation mechanics and gas transport, while distinguishing breathing and gaseous exchange from cellular respiration.
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