Now the diaphragm. This is an incredible muscle. It's a muscle that really is responsible for the
mechanics of breathing. Now look at our graphic there. You don't see any lungs there, we're
just showing you the rib cage, the sternum, and you can see the diaphragm. Now look at that.
On right side is a little higher than the left side and this is a thin skeletal muscle. So it's what
separates my thoracic cavity from my abdominal cavity and if this muscle isn't working, I'm not
breathing without assistance. So let's go back to that air molecule. Nasal cavity #1; the
pharynx in the throat; the larynx, the voice box so we're 1, 2, and 3. Next, the trachea where it
bifurcates into the 2 main bronchi and then the primary or main bronchi are made up of
cartilage and smooth muscle. Alright, so we hit the first 5 stops on our trip. Now we're going to
go to #6, the main bronchi where they divide into the smaller sections. Now, they're cleverly
named, look at that; secondary bronchi, tertiary bronchi. Each one becomes a little bit smaller.
Now the tertiary bronchi divide into smaller diameter bronchioles and those are all the way
throughout the lungs. So, you filed it all the way into the nose, we got down to the mainstem
bronchi where they divide into smaller sections, the secondary bronchi and the tertiary bronchi,
and it's the tertiary bronchi they go into even smaller diameters that we call bronchioles. So,
as we go through the respiratory tract it becomes smaller and smaller and smaller.