What does each part of the bunch of grape model represent, in relation to the breathing system?

The respiratory system is the set of organs, which allows breathing, that is to say, the gaseous exchanges between the body and the environment.
The respiratory system can be easily assimilated to a bunch of grapesThe main stem of this branch of grapes is the trachea. then divides into smaller ducts called bronchi. Next,  it branches into even smaller branches called bronchioles.
The grapes themselves are the alveolar sacs that are branched with the bronchioles. (each grape is an alveolar sac, the functional unit of the respiratory system).