The trachea branches into the left and right bronchi which each lead to a lung where the bronchi subdivide into smaller tubes called bronchioles. Each bronchiole ends in a small sac called an alveolus which allows oxygen from the air to enter the bloodstream via tiny blood vessels called capillaries.
Bronchioles, alveolus, and capillaries are vital parts of which bodily system?
respiration |
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digestion |
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nervous |
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circulation |