‹ Biology simulationsBiology · AS Level 9700 · 9 Gas exchangeFive 3D simulations covering Topic 9.1 The gas exchange system. Explore the airways, cut through their walls, watch cilia clear mucus, follow gases across the alveolar wall and narrow a bronchiole.
Air passes down the trachea, into the bronchi, through branching bronchioles and into millions of alveoli surrounded by capillaries. Click each part.
The tissues in the walls change from the trachea to the alveoli. Pick an airway to see its wall in section, and click the tissues.
| trachea | bronchus | bronchiole | alveolus | |
|---|---|---|---|---|
| cartilage | C-shaped rings | plates | none | none |
| ciliated epithelium | yes | yes | yes (larger ones) | no |
| goblet cells | yes | yes | few or none | no |
| smooth muscle | yes | yes | yes, a lot | no |
| elastic fibres | yes | yes | yes | yes |
Goblet cells and mucous glands make mucus that traps dust and bacteria. Cilia beat to sweep it up towards the throat. See what cigarette smoke does.
Oxygen diffuses from the air in the alveolus into the blood, and carbon dioxide diffuses the other way, across two thin layers of squamous cells. Breathing keeps the gradients steep.
Smooth muscle can narrow the bronchioles; elastic fibres stretch when we breathe in and recoil when we breathe out. Breathe, then trigger an asthma attack.
Five interactive 3D simulations for Cambridge AS Level Biology 9700 topic 9 Gas exchange: the trachea, bronchi, bronchioles, alveoli and capillary network, the distribution of cartilage, ciliated epithelium, goblet cells, mucous glands, smooth muscle and elastic fibres in the airway walls, cilia and mucus keeping the airways clean and the effect of smoke, diffusion of oxygen and carbon dioxide between alveoli and capillaries with ventilation and blood flow, and smooth muscle and elastic fibres in breathing and asthma.
Five 3D simulations covering Topic 9.1 The gas exchange system. Explore the airways, cut through their walls, watch cilia clear mucus, follow gases across the alveolar wall and narrow a bronchiole.
Gas exchange is a free, browser-based simulation for Cambridge International AS & A Level Biology 9700 (topic 9 Gas exchange). The course is assessed in Paper 1 (Multiple choice), Paper 2 (AS structured), Paper 3 (Advanced practical), Paper 4 (A Level structured), Paper 5 (Planning, analysis, evaluation). Syllabus for examination in 2025-2027. There are 5 tabs, each a self-contained experiment with its own controls and live readings, and nothing to install: it runs on a laptop, tablet or classroom projector.
Full syllabus map: AS Level Biology 9700 topic 9.
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