 So this is the demonstration of the posterior chest wall. This is a prone cadaver So this is the left side of the chest wall and we are demonstrating this from the left side of the cadaver In order to demonstrate the chest wall posteriorly, we have to reflect the following structures First we reflected this muscle here This is the erythrospinate part of the erythrospinate which is known as the Iliocostallus. This is the posterior layer of the thoracolumbar fascia that we have reflected and this is the other part of the Iliocostallus The next muscle that we have reflected is this one This is the longasmus. So now we have reflected the longasmus also And the third muscle that we have to reflect was this one This is the spinalis So we reflected these three muscles of the erythrospinate and this is the remnant of the latsomus dorsi Which also we have reflected. Superiorly, we had to retract the scapula with its attached muscles And we can see the remnant of the latsomus dorsi here also Immediately we reflected the trapezius muscle and we can see the trapezius muscle here. Having reflected these muscles, we see the space here These are the transversal spinalis muscles which are located deep to the erythrospinate muscles and this muscle that we see in front of us This is the Semi-spinalis and deep to that will be the multifidus and the rotators These transversal spinalis muscles as the term implies they are located between the spinalis process Which is here and the transverse process of the vertebrae which are here That's why they are called transversal spinalis muscles. They are the deep intrinsic minor group of Muscles at the back. Extending from the transverse process to the rib. We have these ligaments These are known as the lateral cost of transverse ligament. This is one lateral cost of transverse ligament here This is another lateral cost of transverse ligament. Let me first mention accessory muscles of respiration that we can see here We can see this muscle here with a shiny aponeurotic expansion fibers here This is the cilidus posterior superior and we can see that the fibers as they go down Laterally they become more flesh Then we have another set of fibers, which are very similar in appearance We can see that these fibers are very shiny aponeurotic and Further actually they are more fleshier. This is the cilidus posterior inferior The cilidus posterior superior is responsible for Elevation of the ribs and the cilidus posterior inferior is responsible for depression of the ribs Both of them have proprioceptive function. The cilidus posterior inferior was located under the latsomus dorsi muscle Which we can see here The cilidus posterior superior is located under the rhombus and the levitas and we can see the remnant of the rhombus major here And the rhombus minor higher up. Now let me point out another accessory muscle of respiration that we can see here If we look closely We can see these muscle fibers coming down from the transverse process above to the rib below Next from the transverse process above the rib below from the transverse process above to the rib below These are the levitaries costorum They go obliquely down and therefore we have already guessed it. Their action is to elevate the ribs Now if you look very closely, we can see a small triangular space bounded by the levitaries costorum the inter-transverse ligament and the lateral costor transverse ligament and In between this triangular space We have a neuro vascular structure coming out and that is the dorsal rami of the spinal nerve which supplies the Muscles of the back and we can see we have picked up one of those and we can pick up another one here also These are the dorsal rami of the spinal nerves which come out through this triangular space bounded by the levator is costorum the inter-transverse Ligament and the lateral costor transverse ligament. Now let's mention a few things about the Back proper. We can see the ribs. They are taking attachment from these transverse process of the vertebrae This is where the tubercle of the rib articulates We cannot see the head of the rib articulating because it articulates with the body which is deep inside Then we see that the ribs are making a bend here and we can see the bend all along down like this This is referred to as a costal angle. This is the place where the rib makes a bend From back slightly towards the lateral aspect. Next what we see are the intercostal muscles here The muscle that we see in front of us This is the external intercostal muscle and we can see the direction of fibers are like this the way my fingers are pointing We have split in this space We have split the external intercostal muscle and I'm removing it and I've separated them with my finger And as I separate them we can see the muscle deep to that that is the Internal intercostal muscle and if you look very closely We will see that the fibers are at right angles to the external intercostal muscle Not only that if you look further medially We will see that the muscle disappears and it gets replaced by a membrane and that membrane is referred to as the internal intercostal membrane in contrast to the external intercostal muscle The internal intercostal muscle as it goes closer towards the vertebra It becomes membranous the external intercostal muscle becomes membranous anteriorly where it is called the external intercostal membrane Now I will point out the next important structure in the posterior chest wall and for that We have again completely separated this rib and this rib and we have retracted it far and wide And we can see this neuro vascular structure under my finger This is the strained to coastal artery and the intercostal nerve The first intercostal artery is here and the intercostal nerve is below that They run in the coastal groove where my finger is located and the muscle which is just in front of this is the innermost intercostal and the subcostal muscle and deep to that will be the endothoracic fascia and we can see the neuro vascular structures running here We can see the neuro vascular structures in this view also. This is the nerve and This is the artery Whenever there's any compression injury of the chest like for example a steering wheel compression hearing road traffic accident in a car The weakest point of rib which fractures is the postural lateral angle of the rib where the rib curves from posterior to anterior And that is a site where it can fracture by indirect compression if minimum three adjacent ribs Fracture in at least two places then it produces what is known as a flage chest when we auscultate the posterior chest wall We auscultate the lower lobe of the lung and before I conclude I want to show one more thing so for that I have put back the lexibus dorsi in its place and I put back the Scapula also in its place and I'll put back the rhombus major also in its place and The trapezius also in its place though the spaces are wide apart because we have retracted them This triangular space that we see here This is referred to as a triangle of auscultation. It is bounded by the trapezius The lexibus dorsi and the scapula and the floor is formed partly by the rhombus major So this triangle of auscultation is relatively free from muscles and it is used to auscultate the lower lobe of the lung So these are some of the findings which we noted in the posterior aspect of the chest wall of this cadaver Thank you very much for watching Dr. Sanjay Sanyal signing out if you have any questions or comments, please put them in the comment section below. Have a nice day