 A quick demonstration of the entry chest wall which we have removed from this canal here. So, you can see the sternum here, the manubrium sternum. So, this is the jubbler notch or the supra sternum notch and here there is a facial space which is referred to as a supra sternum space of burns which we shall see in the neck. This is the manubrium sternum angle of Louis and this is where it articulates with the body of the sternum and these ridges that we feel on the body of the sternum these are the fusion of the sternum bray and this portion that we see here is the zephyr process. So, this is the subcostal angle zephyr process is felt in the epicastry. This manubrium sternum angle of Louis is where the second rib is attached. This is the first rib and this is the articulation with the clavicle. So, sternum clavicular joint and this is the sternum costal joints and these are the second, third, fourth, fifth, sixth, seventh ribs. Seventh rib articulates with the zephyr sternum joint. So, these are the true ribs. If you notice the ribs this is the bony portion of the rib and this is the cartilaginous portion the bony portion and the cartilaginous portion. So, this is the the articulation the sternum costal articulation is by means of the cartilage. So, this is the introsius part and this is the intracondral part of the spaces. How do we measure the spaces? The usual starting point is the manubrium sternum angle of Louis which we can all feel. So, once we feel that then we know that this is the second rib. So, the space just below that is the second space and then we count third space, fourth space, fifth space, seventh and sixth space and downwards like that. So, that is the way to do it. So, this is a quick demonstration of the overall overview. The ribs are the bony portion is covered by periosteum and the cartilaginous portion is covered by pericondrium which I shall mention in the clinical correlations just a little later. This is the pericordium condrium which we have split open. Now, let us take a look at the muscles. The muscle that you see in front of us this intercostal muscle. These are the external intercostal muscle and you can see the directional fibers are parallel to the slope of the ribs. This is the external intercostal muscle. It is like as if we have put our hand in our pocket and therefore, the contraction of the external intercostal muscles are responsible for elevation of the ribs during forced respiration. Anteriorly, the external intercostal muscle is absent and I have lifted up a membrane here. You can see the same thing on this side also. So, this is the external intercostal membrane. So, the anterior portion, the cartilaginous portion, the external intercostal muscle is absent. It is replaced by a membrane. In one place, we have removed the external intercostal muscle. This is the external intercostal muscle to show you the underlying muscle and this is the internal intercostal muscle. And you can see that the directional fibers of the internal intercostal muscle is in the opposite direction. It is like as if we have put our hand in the opposite chest wall. The internal intercostal muscle has got two components. One portion which is between the body portion of the ribs is called the intraocious part. The internal intercostal muscle continues right up to the sternum. At this portion that we see here is the intercontral part. This portion, the body part, intraocious part is responsible for depression of the ribs because it is at right angles to the slope of the ribs. While the intercontral part because it is parallel to the slope of the cartilaginous part, it is responsible for elevation of the ribs. The internal intercostal muscle posteriorly does not extend up to the vertebra and there it is replaced by the internal intercostal membrane. So, this is what we can see here. Now, I will turn this specimen to show the inner surface of the antihistral wall from inside. So, again we can see the inner surface of the maribrous sternum with two muscles attached to it which are actually muscles of the neck with sternum hired and the sternum hired muscles respectively. This is again the maribrous sternum joint. This is the body of the sternum and this is the zephoid process. The points to be noted are this glistening surface that we can see on this side. This is the endothoracic fascia which is covered by the parietal plura. Endothoracic fascia covered by the parietal plura. We can see a few salient points here. First of all, on this side we have removed some of these superficial structures to show you these slips of muscle fibers. This is the transversus thoracus muscle. It is present only on the anterior surface. Similarly, it will be present on this side also and we can see some of the fibers here. So, this slip of fiber, this slip of fiber is the intertransversus thoracus. This is the one which continues into the abdomen and merges with the transversus abdomenis muscle. The next thing that we notice are these two neurobascular structures, one on either side. The vein on the medial side and the artery on the lateral side. Vane on the medial side, the artery on the lateral side. This is the internal thoracic artery and vein. Internal thoracic is a very important. This arises from the subclavian artery on either side and it runs down on either side of the sternum. And as it descends down, it disappears between the transversus thoracus and the internal intercostal, which is further anteriorly and you can see it is disappearing. This is the one which is responsible for giving the anterior intercostal vessels, artery and vein. So, up to the sixth space, we have the branches coming from the internal thoracic artery. What about the seventh, eighth and ninth space? For that I have split open the transversus thoracus here and I am lifting it up here. So, I have lifted it up here on this side and this is where I have split it open. And we can see that the internal thoracic artery is dividing into its terminal branches here. This and this. This is the musculophrenic branch. This is one of the terminal branch. The other terminal branch is the superior epigastric which runs into the abdomen. Similarly, on this side also, we have split it open to show you the division. And I have split it open and we can see the division here. We can see the musculophrenic and the superior epigastric. So, that brings me to the intercostal arteries on the anterior aspect. As I mentioned, the first six spaces are given up by the internal thoracic. The seventh, eighth and ninth spaces, they are given up by the musculophrenic. Similarly, on this side also, the seventh, eighth and ninth antiointercostal arteries are given up by the musculophrenic. And these antiointercostal arteries, they run in the neurovascular plate and then they come with this posteriori and then instruments with the posterior intercostal arteries. So, that is another thing which I wanted to show you on this surface. Now, let me mention a few important clinical correlations. Let me turn the model again. We can do, when we are doing any procedure in the intercostal space, we have to remember that this is the lower border of the rib above and this is the upper border of the rib below. Here, we have the main neurovascular part of the running and here we have the collateral vessels running. So, we have to anesthetize both. And when we are doing any procedure, we have to avoid both the neurovascular structures. So, this is the place where we insert our instrument, either the needle or the intercostal tube. That is one point. That is called intercostal chest tube brainage for thoracentesis. When we are doing a thoracotomy, we can do an anterior thoracotomy and the procedure for that is to split open the pedicondrium, as you can see here, by making an H-shaped incision, as I have done here. Another H-shaped incision has been done on this side also. And that way, we can split open the pedicondrium and we can shell out the cartilaginous portion and then we can enter the chest wall. So, this is the procedure for the anterior. If you want to do a posterior lateral thoracotomy, this is not the posterior part of the chest wall, but I will demonstrate it of this. We do a similar thing. We split the pediosteum here and we deflect the pediosteum on either side and we remove the rib in the bed of the pediosteum. That way, we can take advantage of the space above and the space below to do the thoracotomy, enter the thorax. So, that is done for posterior lateral thoracotomy and this is the anterior thoracotomy. Let us again turn back the model. To mention some important clinical correlation pertaining to the internal thoracic artery, as I told you, it is a very important artery. This internal thoracic artery is used for coronary bypass drafting and that is known as, especially the left side is used and that is known as, this internal thoracic is also referred as internal mammary artery because it gives very important perforating branches which supply the breast to the female that is also referred as the mammary artery and therefore, this bypass which is done using the left internal thoracic or internal mammary is referred to as the left internal mammary anastomosis or left internal mammary coronary bypass drafting. So, these are some of the points to be mentioned about the chest wall on the external surface and the internal surface. Thank you very much for watching. Dr. Sanjay Sanyath signing out.