Question

Which statements explain the gas exchange that happens at the alveoli? Check all that apply.

Carbon dioxide moves from the air in the alveoli to the blood.
Carbon dioxide moves from the blood to the air in the alveoli.
The capillaries that surround the alveoli exchange both carbon dioxide and oxygen.
The capillaries that surround the alveoli exchange only oxygen.
Oxygen is absorbed by the blood in the capillaries that surround the alveoli.
Oxygen is the air we breathe out when we exhale.

Answer 1

Correct choices:
- Carbon dioxide moves from the blood to the air in the alveoli.
- The capillaries that surround the alveoli exchange both carbon dioxide and oxygen.
- Oxygen is absorbed by the blood in the capillaries that surround the alveoli.

Why the others are incorrect:
- Carbon dioxide moves from blood into the alveolar air (not from alveolar air into blood).
- The capillaries exchange both gases, not only oxygen.
- Exhaled air contains CO2 (and some unused O2), so it’s incorrect to say oxygen is what we breathe out (we primarily exhale carbon dioxide).