Ventilation and the exchange of gases in the lungs
Ventilation moves fresh air into the lungs and stale air out. This keeps oxygen levels high and carbon dioxide levels low at the alveolar surface, so diffusion into the blood continues rapidly.
Real World
Elite cyclists like Tour de France riders develop higher tidal volumes through training, meaning each breath refreshes more alveolar air and steepens the oxygen gradient into the blood more effectively than in untrained individuals.
Exam Focus
Always explain how ventilation maintains the concentration gradient — stating 'fresh air comes in' without linking to diffusion will not gain full marks.
Evaluation Scaffold
A four-step framework for high-quality evaluation. Use this for 'assess', 'evaluate', and 'to what extent' questions.
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