 Hey everybody, Dr. O here, this video is going to cover the lungs. We've already covered the bronchial treat that's inside of it, but we're going to start with the apex of the lung is on the top and the base is on the bottom. Well, the reason I bring that up is because the opposite of the heart. The base of the heart is on the top and the apex is on the bottom, so the apex are the pointy areas there on the top of the lungs. The base of the lungs is actually touching the diaphragm, which is why when the diaphragm contracts it changes the size and shape and pressure most importantly in the thoracic cavity, which plays a massive role in breathing. I'll show you an image in a little bit, but the lungs are going to be covered by the parietal, visceral and parietal pleura, so they're in the pleural cavity there. Looking at the lungs, you can see here that the right lung on the left-hand side of the image has three lobes, superior, middle and inferior. The left lung has a superior and inferior lobe. The reason there's not a third lobe of the lung is because that's where the heart is sitting. The cardiac notch is what gives your thoracic cavity space for the heart to cram in there. That's why you have more lobes on the right-hand side than the left. The right lung is going to be shorter than the left lung, but it's still going to be a lot bigger. The reason it's shorter is because the liver is bumping up right underneath the diaphragm. The left lung, think skinnier because of the heart, but a little bit longer. Right lung is going to be a little bit shorter but much wider because there's no heart there in the space. What else? Remember that you can see the bronchial tree inside of here as well. The left and right primary bronchus are going to be what actually enters the lungs. The right bronchus is going to be a little more horizontal and wider because it has to feed three lobes instead of two. Then you're going to have the five secondary bronchi, one for each lobe. Then you're going to have that 18 or 19 tertiary bronchi, one for each bronchopulmonary segment. Then you have that branching and branching that continues. This is a really cool image that shows that pleural cavity that the lung is actually in. On the right hand side, you can see it the best. You see the visceral pleura is going to be on the lung itself and the parietal pleura is going to be lining the cavity the lung is in. Between those two, you're going to have that pleural space or pleural cavity which is full of a cirrus fluid. Usually when we talk about these body cavities, we talk about the cirrus fluid being important for reducing friction. That's absolutely true here as well. You don't want there to be any trauma when you're breathing. The cirrus fluid does lubricate, but it has one other really important job here. It actually maintains the tension between the visceral and parietal pleura so that when your ribs do expand and your diaphragm does drop, it actually will pull the lungs with it, making the lungs larger so that the pressure will drop and you can inhale. Not only is it a lubricant, but it's also in a d-sib. It holds these two cavities, these two linings close enough together so that changes in the outside of the thoracic cavity caused by the diaphragm dropping and the ribs expanding will actually bring the lungs with it as you inhale and then bring the elastic recoil, bring the lungs back to the normal position as you exhale. All right, so that's the structure of the lungs as well as the pleural cavity the lungs are in. I hope this helps. Have a wonderful day. Be blessed.