 Okay, everybody, Dr. O here. In this video, we're going to introduce the respiratory system. So first I want to get this out of the way. Most people don't say respiratory system. I just do. I take a lot of heat for that. Respiratory is just fine, but you're going to hear me say respiratory. I don't know if it's a way to slow me down or what, but respiratory is just fine and probably actually better. So we're just going to introduce the respiratory system here. We've already covered blood, right? We've always covered blood cells and the importance of oxygen, but where does the oxygen come from? From our respiratory system. So I'm not going to go through the detail of all the structures here. I'll cover that in a later video, but I just want to talk about a couple of ways that we classify the respiratory system. So first we have the upper and lower respiratory tract. So you've probably heard of upper respiratory infections and lower respiratory infections. Well the dividing line is going to be the larynx. So some would say the larynx, the entire larynx is the beginning of the lower respiratory system. Others would say that the top half of the larynx before you get to the glottis, the opening to the trachea is still part of the upper respiratory system, but just remember that the larynx is where you see this transition from upper to lower respiratory system. Upper respiratory infections are way more common. So think about sore throats, ear infections, sinus infections, those kind of things. Lower respiratory infections are going to be way more deadly potentially. Think about pneumonia and these types of things. That's the first way to classify the respiratory system is upper versus lower respiratory tract. Then when looking at all the same pieces here, we have what's called the conducting zone and the true respiratory zone. See most of your respiratory system is not involved in the trading of oxygen for carbon dioxide. That's going to be the conducting zone, or sorry, the respiratory zone. The conducting zone's job is to carry air to where we can take the oxygen out and put it into our bloodstream and vice versa with carbon dioxide. It's also going to clean that air, removing debris from it, these kind of things. It's going to warm it and humidify it. So the conducting zone's going to be all the way from your nose and your mouth all the way down to what you see there, what are called the terminal bronchioles. So the terminal bronchioles are the beginning of the actual respiratory zone. This is the terminal bronchioles going into the alveolus, the gas exchange surface of the lungs. That's going to be where we actually trade oxygen and carbon dioxide. So the conducting zone is going to be nose, mouth, pharynx, larynx, trachea, all the way down the bronchial tree until you reach that terminal bronchial. That's when it switches to the respiratory zone and is actually trading oxygen for carbon dioxide. Okay. Quick introduction to the respiratory system and some of the terms we will use as we move forward. I hope this helps. Have a wonderful day. Be blessed.