Airways and lungs
The gross human gas exchange system consists of the trachea, bronchi, bronchioles, alveoli and lungs. The branching airways carry air progressively deeper into the lungs until it reaches the alveoli.
| Structure | Role or position |
|---|---|
| Trachea | Main airway linking the mouth and nose region to the two bronchi. |
| Bronchi | A pair of large airways, with one branch entering each lung. |
| Bronchioles | Smaller branching airways that connect the bronchi with the alveoli. |
| Alveoli | Small air sacs that form the gas exchange surface of the lungs. |
| Lungs | The two organs in the chest that contain the branching airways and alveoli. |
The branching sequence is:
trachea → bronchi → bronchioles → alveoli