 Good day everybody. Welcome to our demonstration of the left lung. I'm Dr. Sange Sanyal, Professor Department Chair. How do we know that this is the left lung? First of all it is smaller than the right lung but more important is that it has got only one fissure. This is the oblique fissure and this divides the lung into only a superior and an inferior lung. So let's take a look at the oblique fissure. The oblique fissure cuts the inferior margin of the lung at the level of the sixth rib and it goes obliquely up and it goes and it meets with the hilum of the lung from the posterior superior aspect. Antero inferiorly it goes to the medial surface and it again meets the hilum of the lung from the anterior inferior aspect. Because of this unique orientation of the oblique fissure it divides the lung only into a superior and an inferior lobe but it also alters the orientation of the lung such that the superior lobe is more in relation to the anterior chest wall and the inferior lobe is more in relation to the posterior chest wall. Therefore when we auscultate the chest wall from the front we see the pathology in the superior lobe and when we auscultate the posterior chest wall we note the pathology in the inferior lobe. That is about the lobes and the fissures. Now let's take a look at the parts of the lung. Many things are similar to the right lung. This is the apex of the lung which is above the first rib and this is covered by the plural membrane of the sipson's fascia. This is the apex, this anterior border which is sharp and this is the one which is located in the costo medistinal recess. This is the posterior border which is blunt and this is located in the costo vertebral recess and this is the inferior border which is also sharp and this is located in the costo diaphragmatic recess. That brings me to the surfaces of the lung. This entire surface of the lung that we see here this is the costal surface of the lung because it is in relation to the ribs and here we can see very prominently the costal markings or the rib markings. These are the depressions the horizontal parallel depressions. These are the depressions produced by the ribs. These are present on the costal surface of the lung. This is the inferior surface of the lung which is also concave and this is the one which rests on the left dome of the diaphragm and it is bounded by the inferior margin of the lung and this surface is the medistinal or the medial surface of the lung and this patient apparently had some lung pathology. That's why the consistency of a lung is quite hard. It should not be it should be more spongy and there were plenty of plural additions which tore off the visceral pleura at the time of separation from the chest wall. There's a unique feature of the left lung which is not present on the right lung. There is a notch here in the anterior margin and this is not present on the right lung and this is known as the cardiac notch because it is in relation to one part of the heart which I should tell you just now and below the cardiac notch there is a small projection and this small projection is called the lingular process or the lingula which is again is present only in the left lung but not on the right lung. Cardiac notch and lingular process. Before I proceed any further there's one point I need to mention that when the peratal pleura is getting reflected onto the chest wall on the left side at this region of the cardiac notch and the lingula the peratal pleura moves a little away from the chest wall and as a result of which the heart the pericardium of the heart becomes directly in contact with the chest wall and that portion of the pericardium in relation to this region is called the so-called bare area of the pericardium which is the site which we use for pericardium synthesis. Now let's come to the medial surface or the medial surface of the lung and look at the important landmarks and the relationships so this central portion that we see here this is the high lung of the lung again we can see a big depression here this is the cardiac impression but in the case of the left lung this cardiac impression is produced by the left ventricle because the left ventricle is so big that is the reason why it produces this notch in the anti-margin which we refer to as the cardiac notch so this is the ventricular area or left ventricular area of the lung then we notice this oblique curved groove here above the high lung running from superior and posterior all the way down this is the arch of aorta and the descending thoracic aorta this is the impression of the aorta the aortic impression the aorta as we know is on the left side of the chest wall this small groove that you see here is the left subclavian artery groove groove produced by the left subclavian artery at the lower part of the aorta just in front of that this area a little bit of this is related to the esophagus because as we know when the aorta descends down and the esophagus descends down in the lower part the aorta moves behind the esophagus the aorta moves to the right and the esophagus moves to the left so therefore this small portion is related to the esophagus here again in front of the high lung we have the phrenic nerve and behind the high lung we have the aegis nerve and this region is also related to the thoracic duct because the thoracic duct is on the left side so these are the important relationships of the medias channel surface of the lung now let's take a look at the high lung structures the high lung is the place where the visceral pleura becomes continuous with the medias channel parietal pleura and the two have a sleeve hanging down part of which has been retained here and this is the remnant of the pulmonary ligament we have the bronchial tree we have the pulmonary artery and the pulmonary vein how do we recognize the bronchial tree we can recognize it by its cartilaginous field and so here in the left we have only the superior and the inferior lower bronchi so we can feel one cartilaginous field here and a cartilaginous field here so this is the inferior lower bronchi this is the superior lower bronchi this big space that we see here this is the pulmonary artery on the left side the pulmonary artery there's only one when it enters the lung and the other openings that we see here these are the various openings of the pulmonary vein because this section has gone a little deeper that's why there are multiple openings but when the pulmonary veins emerge from the lung there will be only two left pulmonary veins and last but definitely not the least we can see these black areas here these black spots here these are the numerous macrophage laden lymph nodes in the hilum of the lung and these are called the broncopulmonary or the hilal lymph nodes so these are the structures that are in relation to the hilum of the lung the broncopulmonary structures that's all for now thank you very very much for watching ladies and gentlemen the passengers are signing out have a nice day if you have any questions or comments please put them in the comment section below thank you for watching and make sure you like this video and click the subscribe button