 Today, we're going to talk about the respiratory system. The respiratory system is basically this giant series of tubes. And the tubes open to the outside world and allow air from the outside world to enter your body in much the same way that food enters your body. It allows the air to get close enough to the blood. It's actually ever mix, but it allows the air to get close enough to the blood so that gas exchange can occur. So the primary purpose of the respiratory system is gas exchange. Now, hopefully after all your experiences in general bio, hopefully you know that gas exchange means we're going to get oxygen in and we're going to get carbon dioxide out. And this is our exchange. Oxygen comes in, carbon dioxide gets out. Oxygen comes in and gets in the blood, carbon dioxide gets out, gets back into the lungs, and you blow it back out again. Primary function of the respiratory system, but it does some other stuff. Because the respiratory system is essentially a series of tubes that are connected to the outside world, they're lined, and the tubes are lined with mucus membranes. And one of the functions of the respiratory system is to condition the air. Now, you can imagine, I mean air is harsh, especially if you're like in a freezing area or a really dry area. Your respiratory system plays a role in warming the air, humidifying the air so that it's in a good, friendly, kind state so that gas exchange can occur. The respiratory system is responsible for what I'm doing right now, which is vocalizing. Indeed, the respiratory system, we breathe in air and then we flap our vocal cords, no joke. And the flapping, holy flapperama, that creates sound. I mean, seriously. Then we throw our tongue into the mix and we do a little bit of magical movements there, and you understand what I'm talking about right now. Or maybe you don't understand what I'm talking about, in which case, I apologize profusely. The respiratory system, really important, is involved in smell. The lining of the upper nasal cavity is covered in what's called an olfactory epithelium. The olfactory epithelium has special receptors embedded in the tissue, and they pick up chemicals that come into your lovely nose and allow you to smell. And the final thing, the respiratory system, mucus membranes, lots of mucus, lots of goblet cells, lots of aphensilia lining the airways. It plays a role in basically protection, allowing, preventing stuff from getting in your lungs, which is why, I think this is the first time I've told you in this lecture series, don't smoke. If you smoke, you compromise your respiratory system's ability to protect you from outside invaders, and it's not good for you. Those are our functions of the respiratory system. Now we're going to go through the tubing, starting up here, and ending in our lungs, and see what happens in each of these places.