Standard Science Primary 5 Systems

What happens to the air when it enters the air sacs in the lungs?

A Nitrogen is absorbed to help with digestion.
B Oxygen leaves the air sacs and enters the blood.
C Oxygen and carbon dioxide both enter the blood.
D Carbon dioxide leaves the air sacs and enters the blood.
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Worked Solution

Step 1: Air sacs (alveoli) are surrounded by blood vessels. Step [2-9]: Oxygen in the inhaled air is at a higher concentration than in the blood. Step [2-9]: Oxygen diffuses through the thin walls into the bloodstream for transport.

Correct answer: Oxygen leaves the air sacs and enters the blood.

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