 So this is going to be a demonstration of the outer surface of both the lungs. This is the right lung and this is the left lung. Let's take a quick look at the parts of the lung. This is the apex of the lung. This is the base of the lung or the diaphragmatic surface. This is the medial or the medial-strainal surface of the lung and this is the costal surface or the lateral surface of the lung. The same thing we can see on the left lung also, apex, base, lateral surface, costal surface and the medial-strainal surface or the medial surface. We shall focus more on the outer surface of the lung. This is the anterior margin of the lung. This is the one which fits into the costal medial-strainal recess of the pleural space. This is the inferior border of the lung. This fits into the costodiaframatic recess and this thick portion that we see here fits into the costovertibular recess between the ribs and the thoracic vertebrae. To see the same thing here, this is the anterior border which fits into the costomedial-strainal recess. This is the inferior border which fits into the costodiaframatic recess and this blunt posterior surface fits into the costovertibular recess. I would draw your attention to the outer surface of the lung. Here we notice a number of salient points. First of all, this shiny structure that we see here and a little bit of that we have lifted up here. This is the visceral pleura. It's thin and it's firmly adhering to the surface of the lung. To see the same thing here, this is the visceral pleura here. Incidentally, in this particular cadaver, we notice that the visceral pleura is very thick and it was densely adhering to the lung. I shall mention more of that in the clinical correlations. We can see the subplural lymphatics are engrossed with macrophages which have ingested the carbon particles. If this had been a smoker, then the whole surface would have been densely infiltrated with such black carbon particles. The next thing we notice are the fissures. This is the right lung, so therefore it has got two fissures and three lobes. This fissure that we see here which is being traced by my finger which is going obliquely up, this is the oblique fissure. It cuts the inferior border of the lung at the level of the sixth rib and it goes obliquely posteriorly up and it enters into the medial surface from the posterior superior aspect. The next fissure that we see on the right lung is this fissure. This is the horizontal fissure. This cuts the anterior border of the lung at the level of the fourth rib and it goes transversely and it meets with the oblique fissure and therefore the right lung is divided into a superior lobe, a middle lobe and an inferior lobe. Superior and the middle lobes are more anteriorly located and the inferior lobe is more posteriorly located. So therefore when we auscultate on the right side, anterior chest wall, we hear sounds pertaining to the superior and the middle lobe and when we auscultate the posterior chest wall, we hear sounds pertaining to the inferior lobe, the right lung. Now let's take a look at the fissure and the left lung. The left lung is smaller and it's got only one fissure and this is that fissure. This is the oblique fissure and therefore the left lung has got only a superior lobe and an inferior lobe and just like the right side, we can see that the superior lobe is more in relation to the anterior part of the chest wall and the inferior lobe is more in relation to the posterior part of the chest wall. Now let's come to the recesses of the pleural space. Recess means a little enlarged pleural space. As I mentioned earlier, the anterior margin fits into the costumidestinal recess. It is the recess between the rib anterior lead sternum and the anterior part of the medial sternum. This fits into the costotaphermatic recess. This is the largest recess in the human body where the inferior border of the lung fits in and this is the site of fluid collection in pleural effusion. Now let's mention a few important clinical points. I would draw your attention to something very special in this particular cadaver. If you were to look at my finger and I'm squeezing the upper lobe of the lung, the right lung and I'm squeezing the upper lobe of the left lung, we can see that it is soft, spongy and we can see fluid coming out. In contrast, take a look at the lower lobe. It is red, pleural surface is thick as I mentioned a little while earlier and it is very hard. Same thing we can notice on this side also and it is bright red in colour. This particular cadaver had bilateral lower lobe pneumonia and we can see that clearly here and that is the reason why this pleura was densely adhering to the parental pleura and we had to separate it out as a result of which part of the surface of the lung got lacerated. So this is a case of bilateral lower lobe pneumonia. The apex of the lung, both the sides, they protrude a little above the first rib and here they are covered by a special layer of endothoracic fascia which is called the Sipsons fascia or the suprapleural membrane with the parental pleura just under it. In this location, if we are doing any supraclavicular procedure like for example removing a deep seated lymph node or even while giving a supraclavicular block of the brachial plexus we can puncture through that suprapleural membrane and we can produce a pneumothorax and it has been well documented including cases seen by the author's own clinical experience. When a patient has got pleural effusion in the costodiframatic recess, as I mentioned, the costodiframatic recess is the most prominent in all individuals. We do what is known as a pleural synthesis or a thoracentesis or a pleural tap. The classical position for doing a pleural tap is through the fifth intercostal space in the mid-axillary line, either the right side or the left side because in such cases, even though the fluid is collected in the costodiframatic recess remember this patient is lying down and when the patient lies down the fluid collects in the para-vertebral gutter on either side of the vertebra. So therefore, we put a needle in the fifth intercostal space the mid-axillary line and we put in a cannula and we drain the fluid and that is called the pleural synthesis. Similarly, in a case of traumatic injury, if a patient has got hemo pneumothorax or a collection of air and fluid then also we can insert a large bore tube through the fifth intercostal space in the mid-axillary line and in that position we can drain both the air and the fluid and we can connect the tube to the underwater sealed drainage. So that is the principle of the procedure for pleural synthesis and drainage of hemo pneumothorax. When we look at the left lung, we notice yet another difference apart from a single fissure. If you look at the anterior border, we notice that there is a notch in the lower part and this notch is called the cardiac notch because it is in relation to the left ventricle and just below the cardiac notch there is a process. This is known as the lingular process. So this is not present on the right lung but it is present on the left lung. Now this also has got a clinical significance. In this region, the parietal pleura, because of this cardiac notch the parietal pleura moves a little away from the anterior chest wall and so therefore in this region where my finger is located the pericardium is in direct contact with the anterior chest wall on the left side only and that portion of the pericardium is referred to as the bare area of the pericardium. So therefore when we have to do a pericardial synthesis we usually choose the left fifth or the sixth intercostal space right next to the sternum or the left side of the infraternal angle and we insert the needle to do a pericardial synthesis by so doing we are sure of not entering through the pleural space on the left side. So that is the significance of the cardiac notch. So these are all the points that I wanted to mention to you pertaining to the outer surface of both the lungs and the respective differences. Thank you very much for watching. Dr. Sanjay Sanyal signing out. David O is the camera person. If you have any questions or comments please put them in the comment section below. Have a nice day.