meet the lungs" at Khan Academy!
The main function of our respiratory system is to "trade off carbon dioxide for the oxygen made by trees" and "give oxygen to blood and blood to organs so they'll function with ease"! (That's from The Respiratory System song.)
We were able to see inside someone's lungs (Tom's!) in a bronchoscopy video - cool!
Do you know: the trachea is lined with rings of cartilage called pseudostratisfied ciliated epithilium?