Okay, let's go back to our air molecule. Now, we've done 1 through 4. Right? We went from the
nasal cavity, and by the way we just numbered the system, you don't use these exact
numbers in real healthcare. This is just our way to illustrate it for you. So we start with the
nasal cavity, right the pharynx, the larynx, the trachea and where it bifurcates into 2 bronchi.
Those were our first 4 stops. Then 5 through 8, we had the main bronchi where they divide into
smaller sections and we have the secondary bronchi, the tertiary bronchi, the terminal
bronchioles, and the respiratory bronchioles. So, great place for you to pause and test your
brain. Pause the video, make sure you're very clear and think as you're walking through
1 through 8. Can you think of a function or a difference or some descriptor about each one
of those 8 stops. Okay, now that you've given yourself a review of 1 through 8, let's break
down the air molecule trip one more time. So the respiratory bronchioles, stop 9, divide into
multiple alveolar ducts. Now we're getting down to the serious business of CO2 and O2
exchange. The docs have alveolar sacs and I see in our drawing we take in that little tiny box
to give you a feel for where it is, you see where it breaks off and becomes smaller and smaller,
smaller parts of the airway. Now we're going to take that little tiny square and blow it up.
That's where you see the other numbers on the right side. See we have, that's where we're
going to have the ducts of alveolar sacs and the alveoli represented by #11, that's where the
actual gas exchange takes place. Okay, so the alveolar sacs and the alveoli, that's where the
actual gas exchange takes place. So it doesn't happen in my nose, doesn't happen in my
pharynx, my larynx, my trachea, or the rhonchi, bronchioles. It has to get way down to this
level where CO2 and O2 exchange actually occurs.