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Gas exchange in lungs





Gas exchange in the lungs happens in the alveoli.

Some of the features of alveoli include:

- thin walls (just one cell thick)

- large surface area

- moist surface

- many blood capillaries [1]

Inhaled and exhaled air

Compared to atmospheric air, exhaled air contains:

- less oxygen

- more carbon dioxide

- slightly more nitrogen [2]

Test for Carbon dioxide

Limewater turns milky in the presence of carbon dioxide, so ...

it can be used to show the differences between inhaled (inspired) air and exhaled (expired) air.

The limewater immediately turns milky on contact with exhaled air. [3]





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