Flashcards · Biology · Exchange and Transport in Animals
The Lungs and Gas Exchange
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What is the windpipe called?
The trachea.
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What does the trachea split into?
Two bronchi, one for each lung.
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What do the bronchioles end in?
Alveoli.
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What are alveoli?
Tiny air sacs where gas exchange takes place.
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What surrounds each alveolus?
A network of capillaries.
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Which gas moves from the alveoli into the blood?
Oxygen.
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Which gas moves from the blood into the alveoli?
Carbon dioxide.
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How do the gases move across the alveolus wall?
By diffusion, down their concentration gradients.
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Why do the lungs have millions of alveoli?
To give a very large surface area for gas exchange.
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Why are the alveolus walls only one cell thick?
To give a short diffusion path.
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Why does a rich blood supply help gas exchange?
It carries oxygen away and brings carbon dioxide, so the concentration gradients stay steep.
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How does breathing help gas exchange?
It ventilates the alveoli, which keeps the concentration gradients steep.
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What happens to the alveoli in emphysema?
Their walls break down, so the surface area for gas exchange is reduced.
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How do you work out the volume of air breathed per minute?
Volume per breath × number of breaths per minute.
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Is air breathed out the same as air breathed in?
No. It has less oxygen and more carbon dioxide.
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Name the part marked X and say what happens there. The alveoli. Oxygen diffuses into the blood and carbon dioxide diffuses out here.
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Label the airways and the structures of the lungs. 
Trachea, bronchus, bronchioles, lung, alveoli and capillary network.