 The pulmonary pleura is the serous membrane which covers the lungs. The lungs invaginate the pleura like so. If we pause the animation and cut the pleura in half now, in life this layer tightly adheres to the lung and is called visceral pleura. This layer sticks to the internal thoracic wall and is called parietal pleura. Parietal models like this one allow us to easily visualize this relationship between lung and pleura. So this is a schematic thorax here. We'll remove the intercostal muscles and then take a coronal cut down through the whole model. You can see the lung here is covered directly by visceral pleura which is continuous with the parietal pleura. The parietal pleura adheres to the walls of the thorax and to the diaphragm below. Let's move to a more complex model now. Here's the parietal pleura. It has its apex about two and a half centimetres above the clavicle. We'll now follow it down the anterior chest wall. It runs down the line of the sternum to the fourth costal cartilage and continues straight down on the right hand side to the zephysternal joint at the bottom of the sternum. The left pleura does not come as close to the midline because of the cardiac bulge. Now at the inferior border the pleura courses around to the side crossing the eighth rib in the mid-clavicular line, the tenth rib in the mid-axillary line and meets posteriorly the T12 vertebra. The visceral pleura here is tightly adhered to the lung and the surface marking of the lung corresponds exactly to that of the visceral pleura and pretty closely to that of the parietal pleura with some exceptions. So the apices are the same, that's why a stabbing in the neck above the clavicle can puncture your lung. Also the anterior border of the right lung corresponds to the parietal pleura down to the sixth chondro sternal joint. The anterior border of the left lung begins curving away at the fourth costal cartilage because of the cardiac notch and curves back at the sixth costal cartilage. Finally the lung traverses around following the sixth rib in the mid-clavicular line, the eighth rib in the mid-axillary line and the tenth rib back in the midline. You should note that this means the lower border of the lung is roughly two rib spaces higher than the pleura. So to quickly recap the parietal pleura covers anteriorly to rib eight, laterally to rib ten, posteriorly to T12. The visceral pleura reflects the shape of the lung itself and covers anteriorly to rib six, laterally to rib eight, posteriorly to T10. Moving on to the lungs now. The right lung has three lobes, upper, middle and lower, with two fissures dividing them. The oblique fissure, separating the lower from the upper and middle lobes, starts at T4, posteriorly, crosses the fifth intercostal space and then anteriorly continues at the level of the sixth rib. The horizontal fissure divides the upper and middle lobe. It starts anteriorly at the fourth intercostal space, moves posteriorly to the level of the fifth rib. So if we take a coronal cut through this model now, we can see the separate layers. We have parietal pleura, visceral pleura, then lung. In between the layers of pleura is the pleural cavity, which contains a small amount of cirrus fluid, which is produced by the pleura itself. If there's no pathology in this lung, these layers will be adhered to one another to enable the tight pressure regulation required for normal breathing. Have a look at the links in the video description if you'd like to navigate around these models yourself. Hit subscribe if you liked the video, thanks for watching and we'll see you next time.