 Hey, team. Today we're going to start our survey of the respiratory system. In the last lecture we talked about capillary exchange, how stuff moves from cells into the capillaries or from the capillaries into the cells. It's very related to the respiratory system as one of the major functions of the respiratory system is gas exchange. Before we can talk about gas exchange, which is the topic of our next lecture, we have to talk about one of the most obvious functions of the respiratory system, which is ventilation or breathing. So why don't we start out with an overall look at functions of the respiratory system. There are two primary jobs that the respiratory system is responsible for carrying out. And the first one is acquiring, that's a good word, acquiring oxygen for body cells. Now, I hope that this question is not confusing to you. Why? Why do we need oxygen for our cells to survive, like done, dead, buh-bye, if you don't have oxygen? Well, please make sure that your answer is not because you'll die without it. That's true, but most of us know that already. Think back to your Bio One days or your general bio experiences with cellular respiration and tell me, what, why, what is oxygen necessary for in cellular respiration? Remember, cellular respiration was the process of taking glucose and turning, using the energy stored in a glucose molecule to produce ATP. And where does that happen? In the mitochondria. How is oxygen related to that? Well, if you remember, and I know you do, oxygen is the final electron acceptor in the electron transport chain in the mitochondria. I hope that it is not, those words are not Greek to you because if you don't have oxygen as your final electron acceptor in the electron transport chain in your mitochondria, you produce a fraction of the oxygen, I mean of the ATP that you can potentially get out of a glucose molecule. So oxygen is critical to energy production. That's why aerobic exercise, you can go longer when you exercise aerobically than you can if you're exercising anaerobically or sprinting. You can only sprint like one time around a track where you can jog. Some people can jog for very long periods of time. That is not like me, but that is okay. It's because when you're sprinting, you are using more energy and you need more oxygen in order to produce that energy. So oxygen, you're cool. We know why it's important. The other thing equally as important is to, an equally important function of the respiratory system is to get rid of what? Carbon dioxide. And you know I'm going here. Why? Why do we need to get rid of carbon dioxide? Who cares? Dude, let's just leave that stuff in there. Please don't. Carbon dioxide, this is the beginning. We will see this again and again. Carbon dioxide plus water, do you remember, turns into carbonic acid, H2CO3, which dissociates into hydrogen ions. H2CO and bicarbonate ions, HCO3 negative. Okay, that, hopefully, I think we talked about it in the very beginning when we dealt with chemistry. Right here is your clue that, dude, we better get rid of carbon dioxide because it will quickly, if we increase the concentration of carbon dioxide, we're going to also increase the concentration of hydrogen ions. That makes something acidic. Blood pH, we're going to have an entire lecture on the importance of maintaining blood pH levels within homeostatic range. So if you don't get rid of your carbon dioxide, your blood is going to become acidic. So these right here are hugely important functions of the respiratory system. Now, that's just part one because part two is to look at, okay, what are the mechanisms of how we carry this out? How do we do this gas exchange that you speak of? Well, first of all, you have to breathe, and that is pulmonary ventilation. Ventilation is just moving air from the atmosphere and into the lungs. This is the entire topic of today's lecture. This is what we're going to talk about. In the next section, in the next lecture, we're going to talk about all the rest of this. Pulmonary ventilation, awesome. Who cares unless you do external respiration? And external respiration is basically gas exchange. So the movement of oxygen in and carbon dioxide out, that's the exchange of gases. And it's gas exchange between blood and lungs. And I'm going to tell you, we're going to learn where exactly this happens. We're going to talk about that in the next one. Well, this isn't actually involved in the respiratory system, so maybe I should make it another color, but it kind of is because it's about moving gases around. So we're going to have to transport gases to the cells, and you can also think of that as transporting carbon dioxide back to the lungs. We're going to transport oxygen to the cells. We're going to transport carbon dioxide back to the lungs. Through the circulatory system, heart's going to do the job of beating, vessels are going to do the job of carrying the gases. And then once we get to the cells, we have internal respiration. And internal respiration is gas exchange between blood and cells. The body cells need to get the oxygen and get rid of their carbon dioxide. That's considered internal respiration. It's not to be confused with my friend and favorite cellular respiration. And what cellular respiration? Pardon the very long pathway. That's cellular respiration. Cellular respiration takes place in the mitochondria in the cells that are receiving the oxygen. Cellular respiration, one of the products of cellular respiration is carbon dioxide. So then carbon dioxide has to be dumped back into the blood via internal respiration, transported back to the lungs, stuck into the lungs via external respiration, and pulmonary ventilated out. Pulmonary ventilatedness, I don't know how I'm going to put that into words. Makes perfect sense. Now, what? Now we're breathing. We're not going to talk anymore about any of these except just to keep context. Why are we doing all this stuff? But today our whole focus, the whole lecture is on this one part which hopefully does not bode ill for us. So let's talk about the anatomy and the respiratory system that allows us to do pulmonary ventilation.