 So, this is the demonstration of the antri-chest wall. We have completely removed the antri-chest wall from this cadaver and first we will demonstrate the structures as you can see them from the front and then from behind. So, this is the manubrium sternum, this is the juggler notch, then we have the body of the sternum here. So, therefore, the manubrium sternum and this body of the sternum they articulate in this place and there is a manubrium sternum joint and we can see just from an angle here. This is called the sternum angle of Louis. The body of the sternum has got multiple ridges on its surface which are the fusion points of the sternum prey and then finally, down below here, we have the zikri sternum which is felt in the epigastrium. This is the zikri sternum articulation. Articulating with the manubrium sternum, we have the clavicle here and we also have the articulation with the first rib. Then we have the second rib. The second rib articulates at the manubrium sternum angle and that is how we count the ribs. We feel the sternum angle of Louis and immediately adjacent to that is the second rib and therefore, below that is the second intercostal space and that's how we count the third, fourth and the fifth. We count the spaces and we count the ribs. So this is about the manubrium at the sternum. Now, let's take a look at the ribs. The first rib articulates with the manubrium as I told you and the first rib is flat and it is not horizontal, it is an angle with the horizontal. The anterior articulation of the first rib is at the level of third thoracic vertebra while the posterior articulation is with the first thoracic vertebra. So therefore, we can see that the first rib, the thoracic inlet is at an angle to the horizontal. This is the second rib, third, fourth, fifth and the ribs continue down. If you trace the ribs, we find that immediately at the attachment to the sternum, they are not bony, they are cartilaginous. So therefore, this constitutes what is known as the sternum costal joints and the articulation between the bony portion and the cartilaginous portion is referred to as the costocondral articulation. In old age, costocondral articulations can ossify and they become brittle and when we are giving an external cardiac massage, if there is any reason, they can fracture there. The first seven ribs are the true ribs, one, two, three, four, five, six, seven because they articulate directly with the sternum. The seventh rib articulates at the zippy sternum joint and the second rib articulates with the menopause sternum joint. Eight, nine and tenth ribs are referred to as the false ribs because they articulate with the seventh costal cartilaginous at what is known as the congro-congro articulation. Finally, the eleventh and the twelfth ribs are called floating ribs because they do not articulate anteriorly at all. Now let's take a look at the muscles that we can see, the intercostal muscles. The muscles that we see in front of us, these are the external intercostal muscles and we can see the directional fibers are going down obliquely. We can liken them to hands in the pocket. In one place, we have removed the external intercostal and we can see that here. We have removed the external intercostal and this is the internal intercostal. Internal intercostal muscles are exactly at right angles. They are as if hands on the opposite chest wall. If we trace the external intercostal muscle further medially as we are doing it here and the instrument has gone in, we can see that anteriorly the external intercostal muscle disappears and it is replaced by a membrane and that membrane is referred to as the external intercostal membrane. The internal intercostal muscle similarly as it goes posteriorly, it gets replaced by a membrane which is referred to as the internal intercostal membrane. So we cannot see that membrane anteriorly. The external intercostal muscle is responsible for elevation of the ribs. Internal intercostal muscle has got a dual function. This portion of the muscle which is in relation to the bony part of the ribs that is responsible for depression of the ribs while the same internal intercostal muscle which are in relation to the cartilaginous part of the ribs as we can see them here. Because they are running parallel to the direction of the cartilage, they are responsible for elevation of the ribs. So to summarize the internautious part of the internal intercostal muscle is responsible for depression of the ribs. The interchondral part of the internal intercostal muscle is responsible for elevation of the ribs. They are also applied by the intercostal nerves but we cannot see the intercostal nerves in the anterior view. They are best seen in the posterior view because by the time they come anteriorly they become very small. Now I want to show you a few clinical aspects. I will show you how to do a thoracentesis. So this is a typical rib and this is another typical rib. So this is the intercostal space. We know that the main intercostal vessels are running in relation to the lower border of the rib above and the collateral branches are running in relation to the upper border of the rib below. So our route for a thoracentesis when we do have to do a plural aspiration or a plural tap should be far from the lower border of the rib above and closer to the upper border of the rib below. We usually approach to the mid-axillary line in the fifth intercostal space. So this is where we put in the dealing and we go like this. So this is the route for doing a thoracentesis or a plural aspiration or a plural tap. If it is necessary to do an intercostal nerve block, remember we have to block two sets of nerves. One is the main nerve which is running in relation to the lower border of the rib above and another is the collateral which is running in relation to the upper border of the rib below. So therefore in order to give an intercostal nerve block, we have to block this nerve and this nerve. So these are the two related procedures that we need to perform in the intercostal spaces. The next thing I want you to notice is one simple step of thoracotomy which I have already demonstrated here. If you take a look at this, this is the costal cartilage here. And this covering of the costal cartilage is called a pericondrium just like a periosteum. And here what we have done is we have made an H-shaped incision and you can see I have lifted up the pericondrium here and the pericondrium here. Similarly, we have made an H-shaped incision and we have lifted up the pericondrium here and we have lifted up the pericondrium here. This is a useful method of doing an anterior thoracotomy. After we have lifted up the pericondrium, we insert an instrument under it and we cut the rib. Similarly, we insert and we cut the rib. So it is a subpericondrial resection. And once we do that, we can expose the chest from the anterior aspect. That is a root for anterior thoracotomy. Why do we cut the rib and under the pericondrium? So that once we put the pericondrium back, the rib can grow back. So that is called subpericondrial or subperiosteum resection of the rib. Another approach to the anterior chest wall is through the sternum and that is known as a sternotomy. There is one more approach and that is a posterior lateral approach where we cut on the ribbed and we make use of the adjacent intercostal spaces to enter and that is known as a posterior lateral thoracotomy. So these are some approaches to the chest wall. So that is all that we can see in this section. Thank you very much for watching. If you have any questions or comments, please put them in the comment section below. Dr. Sanjay Sanyal signing out. Have a nice day.