BRAINCAKERole of Alveoli in Gas Exchange
The rate of diffusion is proportional to the surface area and the diffusion gradient and inversely proportional to the diffusion distance.
Ventilation (inspiration) refreshes the lungs and brings in more oxygen into the lungs. Blood flow removes the oxygen that has diffused from the lungs into the capillary. This maintains the steep concentration gradient.
The walls of the capillaries and the walls of the alveoli are very thin. This ensures a short diffusion distance.
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Key terms in this lesson
- diffusion
- The net passive movement of molecules or ions from a region of higher concentration to a region of lower concentration, down a concentration gradient.
- alveolus
- A tiny, thin-walled air sac in the lungs, surrounded by capillaries, that is the site of gas exchange.
More in Exchange of Gases
- The Lungs
- Mechanism of Breathing
- Inspiration
- Expiration
- Alveoli
- Correlation and Causation
- Risk Factors for Lung Disease
- Smoking and Lung Cancer
All 28 lessons in Exchange of Gases · All AQA AS-level Biology topics