 So this is going to be a demonstration of the posterior chest wall seen from the front. We have completely opened up the thorax. We have removed the two lungs and we are seeing the chest wall from the anterior aspect. We are looking at the interior of the chest wall. So this is a supine cadaver. This is the left side. This is the right side. I am narrating from the right side and the camera person is also on the right side. So first take a look on the left side. I have lifted up a facial sheet here. The inner surface of this sheet is parietal pleura. And this is densely adherent to yet another sheet which is right under it. And that is the endothoracic fascia. If you look further down, we see that it is reticent color. That is because this particular cadaver had lobar pneumonia. And therefore in this region the parietal pleura was thick and it was adherent to the visceral pleura. This endothoracic fascia has got three or four components. The major component is the one which lines the interior of the chest wall, the ribbed surface. And that is known as the costal part. The same endothoracic fascia then continues medially and it covers the medial sternum. And that is known as the medial sternum part. Then it also continues on the dome of the diaphragm. And that is known as the diaphragmatic part. And finally the endothoracic fascia also goes a little above the first rib, which has been removed here. And it forms a small tent shaped structure over the apex of the lung. And that portion is referred to as the sipson spacia of the suprapneural membrane. Superially it is attached to the transverse process of the C7 vertebra. And inferiorly it is attached to the margins of the first rib. So these are all the parts of the endothoracic fascia. Now we shall turn and we shall see the structures on the right side of the thoracic cage. Again we are looking at the posterior thoracic cage and we are looking at it from the anterior aspect. So we have removed the endothoracic fascia here. What are the structures which are visible? This is the phrenic nerve. So let's push that out of the way. This is the thoracic vertebrae here. This is the paravvertebral gutter. And these are the posterior aspects of the ribs seen from inside. First of all let's mention these muscles that we see here. This muscle which is seen from the inside, this is the innermost intercostal muscle merging with the subcostal muscle near the angles of the ribs. That is what we see after we have removed the endothoracic fascia. The next important structure which I would like to draw your attention to are these structures which I have lifted up here. I am going to lift them up one by one and the camera will be zoomed so that you can see clearly. This is one intercostal nerve. Another intercostal nerve, intercostal nerve. So we are seeing the intercostal nerves as they are emerging from the spinal cord. These intercostal nerves, they run in the intercostal space in the costal groove which is located in relation to the lower border of the rib above. And as they run, we can see they are supplying branches to the intercostal muscles. And we can see these branches. They supply branches to the intercostal muscles. When they come to the lateral part of the chest wall, they give a lateral cutaneous branch which pierces the muscles and come to the skin. And this lateral cutaneous branch then divides into an anterior division and a posterior division. And it supplies the skin of that intercostal space. And further, the same intercostal nerve then continues to the anterior chest wall. And for that, I am going to bring the anterior chest wall back here. And this is the anterior chest wall which I have brought back in front of the camera. And I am going to turn it and now we can see the continuation of the intercostal nerve in the anterior aspect. By now it has become considerably thinner because it has supplied many fibers to the muscles. And here also we can see it is supplying branches to the intercostal muscles. So this is one portion of the intercostal nerve, this is another portion and this is yet another portion. And finally, once they reach the anterior part of the chest wall, they pierce through the chest again. On either side of the sternum, they come to the anterior surface as the anterior cutaneous branch. And this then supplies the skin from the anterior aspect. So this is the full course of the intercostal nerves. This is a transverse MRI of the trunk to show the course of the intercostal spinal nerve superimposed upon it. As we notice this nerve as it is running, it is disappearing under this muscle here. It is disappearing under this muscle. In this place, we have split that muscle just to show you the full course of the nerve. So therefore we can trace it all the way up to here. So what is this muscle in which it is disappearing? This is the innermost intercostal which I mentioned continues and merges with the subcostal muscle. And anteriorly, it becomes continuous with the transversus thoracis muscle. This is the innermost layer of the intercostal muscles. That is layer number 3. Therefore, the carry-home message is that these intercostal neurovascular structures, they run between layers 2 and 3. Namely, the innermost intercostal subcostal muscles as layer number 3 and the internal intercostal muscle as layer number 2. In the condition known as herpes zoster or varicella zoster, which we know is a reactivation of chickenpox which has occurred in childhood. The virus remains latent and later in life after 40 years or 50 years, it reactivates and it multiplies and it can travel along these intercostal nerves. It travels with the cutaneous branches and it produces blisters along one intercostal space also referred as shingles. So that is the manifestation of herpes zoster or shingles because of the virus travelling through the intercostal nerves and their cutaneous branches. This is a picture of herpes zoster of the trunk, cursey, CDC, Centers for Disease Control. That is all for now. Thank you very much for watching. Dr. Sanjay Sanyal signing out. David Ho is the camera person. If you have any questions or comments, please put them in the comment section below. Have a nice day.