Respiratory System - Bozeman Biology

Hi, and welcome to the chapter 22 podcast. This is on the respiratory system and the respiratory system you can think of as like your lungs. But more importantly, it's how we get oxygen into our blood supply and get rid of carbon dioxide. The picture I wanted to start with here is a climber on Mount Everest. Mount Everest is so high that the amount of oxygen there is in the atmosphere drops really low. So if you were to somehow transport me right now to the top of Mount Everest, I would instantly pass out. And so climbers who climb Mount Everest have to move up the mountain and down and move up in that allows their body to acclimatize for that. Now athletes have figured out this process as well. And so this is Levi Leipheimer. He's from Montana, just like myself. And what I think finished third in the Tour de France, so very good bike racer. But what he sleeps in or I've read that he sleeps in is something called an altitude tent. And so what an altitude tent does allows you to sleep at about 9000 feet of elevation. And so your body starts to acclimatize to that. What do you do? You actually produce more hemoglobin and your bread blood cells get bigger. And so now when you start to race, you can carry more oxygen. And so you can go faster. The cool thing about an altitude tent is that you can wake up and then you can train at sea level at a really high intensity. And so what is the chapter about? It's simply about moving oxygen in and moving carbon dioxide out. So before we get to the human respiratory system, let's talk a little bit about how it's found in other animals. And so there are two things that are required for any respiratory surface. And the first one is it has to be wet. And the reason why is oxygens moving in and carbon dioxide is moving out, simply through a process called diffusion. And so if it was dry, that's simply not going to work. Second thing that you need is an increase in the surface area. And so one of the simpler forms is just using your skin as a respiratory device. And so amphibians will do this, but same thing here with this worm. And so what they're using is their skin as a surface. And so the capillaries will run right next to that or the vessels will. And so oxygen will simply move from an area of high concentration outside the worm to an area of low concentration inside. If you get to an insect, they've got a little different system. What they've got is they've increased the surface area on the inside. And so they have tiny little holes called spiracles along the side of them. And so what happens is air moves in and it actually branches through these tiny microscopic tubes until each of those tube eventually plums or goes to one individual cell. And some of the bigger insects will have to move their body in and out. Sometimes they use that during flight to actually pump that air in and out, kind of like an accordion. Next, we've got the arrival of gills and gills are found in animals that live in water. And so fish is an example of a gill. And we'll talk more about that in a second, but what you try to do with a gill is you increase surface area. And then we also want to have water rushing over the surface of that. And so there's as much surface area in the gills of a fish as there is throughout the whole rest of their body. As we move on to land, we get actually more oxygen, but we lose that wet environment that we need to move it in. And so we move that wet surface inside our body. And so lungs are folded inside our body to keep it moist and also increased surface area. But they have that similar role. It's moving oxygen in. I want to talk about two of these things. First, let's talk about gills and gills are have high amounts of blood vessels found within it. But they also utilize something called the countercurrent gas exchange. And so if you're a fish, what you do is you move your operculum in and out like that, and as you move it in and out, and you move your mouth like that, you're actually drawing water in an over those gills. As you do that, the blood will actually flow in this direction. And the water will flow in the other direction. And so in science we call that a countercurrent gas exchanger. What does that mean? The water is going from an area of really low oxygen concentration, and it's hitting water that has a slightly higher amount of oxygen concentration. And so we're loading up that water so you can see here that when the blood now has 60% of the oxygen, it's actually meeting water that's more rich in oxygen. And so the cool thing about that is we can utilize up to 80% of the water, excuse me, 80% of the oxygen that comes in is going to actually end up in that blood supply. And compared to those gills, we're really, really inefficient. But the nice thing is that when you move on to land, there's way more oxygen available. And so this is a tick to lick, or sometimes we refer to it as a fish pod. In other words, it was this transition between fish that eventually moved on the land. And this was found maybe 5 years ago. It's pretty famous skeleton. And what it shows is there's great structure in this upper in those upper quadrant of the body, and so it allows them to lift their head up and then gulp air is the idea. And so with the tick to lick, we have the arrival of a primitive lung. And so what is a lung along and now we're talking about the human respiratory system along is really a fractal in what a fractal is is a mathematical representation where you keep following a similar pattern over and over again. So essentially, it's a joint that branches into two, which branches into two, which branches into two, and it keeps branching over and over and over again. And eventually it goes to a dead end. And so if we put some names to some of these things, this is actually called the trachea. And it has these big cartilaginous tubes that actually keep it open. It breaks down into the bronchus and then into the bronchioles and eventually it reaches a dead end. And at the dead end we have what's called an alveoli. Alveoli are these tiny little dead end tubes. And they don't go anywhere. They're so microscopic that our body has to add a chemical called a surfactant to it. And if we didn't have a surfactant to it, it would just be like a balloon where a balloon just collapses in on itself and you wouldn't be able to move air in and out of it. That's one problem with premature babies. They actually don't start producing surfactants. And so that's why they have to put them in a ventilator. When they're born. If I were to grab our little guy here, here's his respiratory system, so you can see this is the bronchus right here into the bronchioles. There's some differences between the two sides of our lungs. The right side of our lungs actually has three different chambers that come from that or three sections. The left side only has two, and that's because our heart moves over into the left side right here. But I don't know if you can see it, but there are these tiny little dots and those tiny little dots are the alveoli, and around those tiny little dots we have capillaries. And what those capillaries are do or they're picking up oxygen. As you breathe, you're simply contracting this diaphragm muscle. And you're also contracting the muscles around your ribs and what that's doing is it is, as you contract it, that's bringing air in or you're reducing the pressure in that chest cavity. As you start to relax your diaphragm, then that air is simply going to move out. And so it's kind of like sucking on a straw. You reduce the pressure, and then that's just going to come in. That's why we have to keep that whole chest cavity. Airtight, otherwise we're going to lose that ability to breathe. How do we control breathing? We control breathing using simple feedback loop. What do we testing for? We're testing for the presence of carbon dioxide. Obviously, as the amount of carbon dioxide in our blood increases, we want to start breathing faster. And then as it decreases, we don't have to breathe quite as fast. And so the interesting thing about carbon dioxide when it comes into our body is it doesn't stay as carbon dioxide. It actually forms something called carbonic acid. And so when you mix water and carbon dioxide, you form carbonic acid. What's that going to do to the PH? It's going to make the PH go down. And so there are two places in our body where we can sense that. One is in the ponds and the medulla of the lower brain stem. And the other part is on the aorta. And so it's going to be testing the blood here or the cerebrospinal fluid here in the brain. If we see a decrease in PH or it becomes more acidic, that means that we're going to increase our breathing rate. How is this blood actually transporting that oxygen transporting that carbon dioxide? Remember, because it has to do those two things. Well, first of all, you need to talk about partial pressure. In other words, oxygen is simply flowing from the alveoli to the capillaries to the arteries in your body to the cells in your body. And it's doing that from diffusion. And so it's always moving from an area of high concentration to low concentration. Carbon dioxide remember is being produced in cellular respiration. And so it's flown in the other direction. It's going from an area of high carbon dioxide to low carbon dioxide. Where does it actually sit? Well, here's hemoglobin hemoglobin is a protein, and we literally have thousands and thousands of these literally millions of proteins in each red blood cell. But in the middle of this hemoglobin protein, we have these iron atoms, and those iron atoms are actually going to bond to that oxygen, just like rust is oxygen combining with iron. Same thing goes on here. The oxygen is going to bind to that iron inside the hemoglobin. Now the other way that we do that is remember we've got to get rid of carbon dioxide. And so here's that carbonic acid I was talking about. Carbonic acid will actually disassociate to form bicarbonate and a hydrogen proton. And this will bind to the hemoglobin as well. And so hemoglobin serves a double purpose. It's able to move oxygen away from the alveoli and it's able to move that bicarbonate back to the alveoli, which then forms carbon dioxide, which we then breathe out. And so the function of the respiratory system is to make sure that our cells have a constant supply of oxygen, but it doesn't work without the next section, and that's going to be the circulatory system.