 Good day everybody. Dr. Sanjay Sanyal, professor of department chair. This is going to be a demonstration of the muscles of the post-abdominal wall and the fascia which was covering them. So this is a supine cadaver. I'm standing on the right side, camera person is on the right side, my assistant is on the left side, and Dr. Thomas is also assisting me, he's also on the left side. So we have completely removed all the contents of the abdomen. What you're seeing here is the post-abdominal wall muscles. So we are going to talk specifically about free muscles, but before that, let me just give a quick overview. This structure that you see here, this is the inferior vena cava. This portion of the inferior vena cava was intra-hypatic, but we have managed to salvage it, and we can see these openings of the hepatic veins here. And after that it appears through the diaphragm. This is the diaphragm. This right dome of the diaphragm, this is the left dome of the diaphragm. This structure that you see here to the left of the inferior vena cava, this is the abdominal aorta, and we can see both of them. The abdominal aorta is dividing at the level of L4 into a right and left common alia cartilage. Similarly, the inferior vena cava is dividing at the level of L5 into right and left common alia veins. This is the left renal vein, this is the right renal vein. This is the right kidney, this is the left kidney. This is the supramacentric artery. And we can see this is the left renal artery, and this is the right renal artery. This is the median archivate ligament, and therefore this is the erotic hiatus. And while we are on this topic, we can see this structure here. This is the right suprarial gland. And likewise on this side, this is the left suprarial gland. So having given this overview, now this comes specifically to the muscles of the posterior abdominal wall. First of all, take a look at this muscle here. This is the iliacus muscle. This takes origin from the hollow of the aela baleum. This is the aela baleum. That's why it is called iliacus muscle. And the tendons, they go down and they merge with the muscle, which I'm going to mention just after this. This was covered by the iliacus fascia. I'm turning the right kidney. We can see this muscle here, and I'm tracing it all the way from here. This is the suas major muscle. The suas major muscle takes origin from T12, L12345, and the fibres they converge down. The fibres of the suas major merge with the fibres of the iliacus to form what is known as the common iliosuas tendon. And the iliosuas tendon then goes under the inguinal ligament through the muscular compartment and gets inserted onto the lesser trochanter. During life, this was covered by a sheet, a tough facial sheet that was called the suas sheet, which is a derivative of the transversalization. And the upper free margin of that makes a curve like this. That is called the medial arcuate ligament, to which is attached some of the fibres of the diaphragm. This is the iliacus, which I've already mentioned. Now let's come and see the same muscles on the left side. We can see the iliacus muscle much more clearly on this side here. This is the iliacus muscle. And this is the suas major. In this particular specific instance, we can see yet another shiny tendon on top of that. This is the suas minor. The suas minor takes origin from T12 and it runs superficially and it does not participate in the same action as the suas major. Instead it forms the iliopectinial arch, which separates the subinguinal space into a right and left compartments. On the right side we cannot see the suas minor, but on the left side we can see that. One word of clinical correlation pertaining to this. If there is an infection of the lumbar vertebrae, like for example lumbar osteomyelitis, pus can track through and it can form an abscess, what is known as the suas abscess. And the suas abscess can then track down like this between the muscle and the suasi, and it will go right down to the thigh and it stops at the level of the lesser trochanter, because that's where the muscle gets inserted. Likewise, on the right side, if there's a pelvic appendicitis, like my finger is located, it can touch the suas major and can irritate the suas muscle and can lead to spasm of the suas. And when the suas muscle undergo spasm, what is the main function of the iliopsoas? Flexion of the thigh. So therefore the patient will have involuntary flexion of the thigh and he will have pain if we try to forcibly extend the thigh. That is called suas test for the corpus test and corpus sign. Now let's come to the next muscle in the posterior compartment. I'll trace my finger instrument on this muscle here. This is the quadratus lumborum muscle. I'm showing it on the right side because we have retracted the kidney and it's clearly visible here. This quadratus lumborum muscle, it takes origin from this ligament here that we can see. This is the iliolumbar ligament. Why is it called iliolumbar? Because it extends from the transverse process of the fifth number vertebrae to the iliac bone. And it also takes origin from the iliac crest and the fibres they go up. And as they go up, they give multiple slips to the transverse process of the lumbar vertebrae and they finally get inserted onto this rib here, the 12th rib. So this is shaped like a quadrangle, that's why this is called a quadratus lumborum. Now this quadratus lumborum has got a few interesting facts. This again was covered by a sheath, which is called the quadratus lumborum sheath, which also has got an upper free margin, which is the lateral archivate ligament, which also gives attachment as you can see to some of the fibres of the diaphragm. This quadratus lumborum sheath actually is the anterior layer of the thoracolumbar fascia. So what exactly is this thoracolumbar fascia? The thoracolumbar fascia is formed by the posterior aponeurosis of the internal transverse abdominis and internal oblique muscle. And this forms the thoracolumbar fascia which splits to cover the quadratus lumborum muscle. So what's the action of the quadratus lumborum? It is for lateral flexion of the spine and it is also for both the sides acting together, it causes extension of the lumbar spine. Now, this quadratus lumborum, as it goes up, as I said, it gets inserted onto the 12th rib here. So here there is a small potential area of weakness where my finger is located right now. Where the quadratus lumborum gets attached to the 12th rib and that area is known as the superior lumbar triangle of Grindfeldt-Leschach. So what are the boundaries of this small triangle? The superior boundary is formed by the 12th rib. The medial boundary is formed by the quadratus lumborum. And the lateral boundary is formed by the internal oblique muscle, which I showed just a little while back. This is the internal oblique. The floor of this is formed by the fascia transversalis. And the roof is formed by the external oblique muscle. So what is the significance of this superior lumbar triangle? In rare instances, this can be a potential area of weakness through which we can get lumbar herniation. So that is the significance of this quadratus lumborum superior lumbar triangle of Grindfeldt-Leschach. So to summarize, we have shown the quadratus lumborum muscle. We have shown the iliacus muscle. We have shown the suvast major muscle. On the other side, I will just quickly and briefly show. This is the iliacus muscle. This is the suvast major and the suvast minor muscle. And this, whatever we can see here, this is the quadratus lumborum muscle. And on top of that, we can see the various branches of the lumbar plexus running on top of that, which we have mentioned in a separate video. And finally, to conclude, we can see this is the right dome of the diaphragm. So these are the lumbar fibres. These are the coastal fibres. And this is the left dome of the diaphragm. These are the lumbar fibres. These are the coastal fibres. So that's all for now. Thank you very much for watching Dr. Sanyal Sanyal. If you have any questions or comments, please put them in the comment section below. Have a nice day. Please like and subscribe.