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Gas exchange is the process by which oxygen enters the blood and carbon dioxide is removed. This takes place in the alveoli — tiny air sacs in the lungs. The lungs are beautifully adapted to make this process as efficient as possible.
The lungs are the organs of gas exchange. Air travels through the following structures to reach the alveoli:
Mouth/nose → trachea (windpipe) → bronchi (singular: bronchus) → bronchioles → alveoli
| Structure | Description |
|---|---|
| Trachea | Windpipe; held open by C-shaped rings of cartilage; lined with mucus and cilia |
| Bronchi | Two branches of the trachea, one going to each lung |
| Bronchioles | Smaller branches of the bronchi; smooth muscle walls can constrict or dilate |
| Alveoli | Tiny air sacs at the ends of bronchioles; site of gas exchange |
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