 Good day everybody. Dr. Sanjay Sanyal, Professor, Department Chair. So this is going to be demonstration of the rectus sheath and the rectus abdominis muscle and a few blood vessels. This is a supine cannibir. We are demonstrating the abdominal wall. I'm standing on the right side. Camber person is also on the right side. So this structure that we see in front of us, this is the anterior layer of rectus sheath on the right side and this is the anterior layer of the rectus sheath on the left side. How is the anterior layer of rectus sheath formed? It is formed by the union of the aponeurosis of the external oblique muscle of the abdomen, which is this muscle. And the anterior leaf of the internal oblique muscle of the abdomen, which is this muscle here. These two fuse to form the anterior rectus sheath, which covers the rectus muscle from front. And that is what is seen in both the sides. Then there is the posterior rectus sheath, which I will show you just now. And that posterior rectus sheath is formed by the posterior leaf of the internal oblique muscle and the aponeurosis of the transverse abdominis muscle, which is seen here. We have split open the rectus sheath. So I'm reflecting the anterior rectus sheath on the right side. And this other leaf. And we can see the muscle inside. This is the rectus abdominis muscle. We will do the same thing on the other side also. I'm reflecting the anterior layer of rectus sheath on the left side. And we can see the rectus abdominis muscle here. The rectus abdominis muscle is a very long muscle and as the term implies, rectus means straight. It is the most powerful muscle of the abdomen. It takes its origin, the proximal attachment, from the pubic sephysis where my finger is located and the pubic rest on each side. And the muscle then goes up and it fans out slightly. And then it gets inserted onto the fifth to the seventh costal cartilages. So therefore, at the placement it gets inserted, there is no posterior layer of rectus sheath because the costal cartilages themselves form the equivalent of the posterior layer. Only the anterior layer is present. This rectus abdominis muscle has got multiple tendinous intersections. And we can see in this particular cadaver, at least four of them. One tendinous intersection is usually at the costal margin and we can see that here. Then there's another one here. The third one is approximately at the level of the umbilicus that is here. And there can be a fourth one and we can see it here. These tendinous intersections break up the action of the long rectus muscle into multiple sections. And therefore, each of these sections can act independently because the nerve supply to the muscle is segmental, which I should show you just now. We would have heard of the term six pack of abdomen. The rule of thumb is the number of tendinous intersections multiplied by two gives the number of packs of the abdomen. So this particular cadaver during life could have had an eight pack of abdomen. Some people who have four pack of abdomen, some people have even ten pack of abdomen. What are the actions of this rectus abdominis muscle? It is useful for increasing the intraabdominal pressure. It is used for sitting up from a lying position. Therefore, people who do abdominal crunches, they develop this muscle. And that is how they develop the packs because this muscle gets hypertrophied and the tendinous intersection is a place where the muscle is attached to the skin. So therefore, it produces the so-called packs. It is useful to flex the lumbar spine. So therefore, it is an anti-lodotic muscle. And because it is inserted onto the goscal cartilages, it also acts as an accessory muscle of respiration during forced exhalation. Like, for example, in M5C, the rectus abdominis muscle comes into play. And it's a very powerful muscle. And this is the muscle which boxers use to develop, to protect their abdomen when they are boxing. Now what we have done, we have cut the rectus abdominis muscle on the right side in its upper portion to reflect it. And that's what we are doing now. And this is the lower part of the rectus abdominis muscle on the right side. By so doing, we have demonstrated two things. One, I will draw your attention to this blood vessel, which is coming from the thorax. This is the superior epigastric artery. It is one of the terminal divisions of the internal thoracic or the internal mammary artery, which passes through the antrolateral hiatus in the diaphragm. And it comes in the rectus sheath and it supplies the posterior surface of the rectus abdominis muscle. And this, anastomosis with the inferior epigastric artery, which I shall show you on the other side. And it is accompanied by its venaecomitantes. The venaecomitantes are the veins accompanying the superior epigastric artery. These venaecomitantes, they form the internal thoracic vein, which then drain into the brachiosophalic vein. The next structure, which I would like to draw your attention to, these nerves piercing the posterior layer of rectus sheath. We can see one here. We can see another one here. We can see one more here, here and here. These are the thoracoabdominal nerves. They pierce the posterior rectus sheath and they supply the rectus abdominis muscle in a segmental fashion. That's why I mentioned that if we do cut the rectus abdominis muscle in one place, the other portion still continues to function because the nerve supply is segmental. The thoracoabdominal nerves are 7, 8, 9, 10, 11 and the 12th one is called the subcostal nerve. Above the umbilicus is 7, 8, 9. At the level of umbilicus is T10 and below the umbilicus is 11 and 12. In this, we can see the posterior layer of rectus sheath but the details of that I shall describe on the other side. So now we have come to the left side of the abdomen and I'm narrating from the left side and the camera person is also on the left side. So we have reflected the left anterior rectus sheath and we can see the left rectus abdominis muscle and here we have cut it in the lower portion. The reason for doing it is because certain structures are visible more on the lower part of this side and when I reflect the lower part of the rectus on the left side, we can see this blood vessel. This is the inferior epigastric artery and we can see that it's accompanied by the inferior epigastric vein which drains into the external iliac vein. Inferior epigastric artery as it rises from the external iliac artery, it runs behind the fascia transversalis and this is the fascia transversalis which I have lifted up here. Here it runs on the posterior wall of the inguinal canal just medial to the internal ring of the inguinal canal and then it enters the rectus sheath. Now I'm going to turn back this muscle to show my finger inside the inguinal canal on the left side. So my finger is now in the inguinal canal and we can see my finger has come here. So this is the path that the inferior epigastric artery takes and this is the cut portion of the fascia transversalis which is the posterior wall of the inguinal canal. While we're talking of the fascia transversalis and the posterior wall of the inguinal canal, now is the right time to show you another very important landmark that we can see in the posterior wall of the rectus sheath. I have stretched out the posterior wall of the rectus sheath and as I mentioned, the posterior wall of the rectus sheath is formed by the half the aponeurosis of the internal oblique and the full aponeurosis of the transverse abdominis. This rule applies only to the upper three folds of the posterior rectus sheath. The lower one-fourth of the posterior rectus sheath is formed only by the fascia transversalis which I have again picked up here. And the junction between the lower one-fourth and the upper three-fourths is visible here and we can see a line. We can see that this is the line, this is the called the archivate line. This line demarcates the upper three-fourths and the lower one-fourths. So therefore, technically speaking, the lower one-fourth does not have a true proper posterior wall of the rectus sheath, it is formed only by the fascia transversalis. And this archivate line gives space for the passage of the inferior epigastric artery into the posterior wall of the rectus sheath. This inferior epigastric artery, anastomosis with the superior epigastric artery which I showed you on the right side. By the same argument, inferior epigastric vein, anastomosis with the superior epigastric vein. And therefore, this provides a site of communication between the tributaries of the superior vena cava with the tributaries of the inferior vena cava. This lateral wall of the rectus abdominis muscle, it forms a groove on the surface of the abdomen which we can see in a thin walled person, thin individual or a muscular person. And that groove is referred to as the linea semilunaris. Rarely we can have a hernia coming out through the linea semilunaris and that hernia is referred to as a spigelian hernia. Since we are already on the anterior rectus sheath on both the sides, which I have lifted up here, we can see that the two anterior layers of rectus sheath and the posterior layers of rectus sheath, they all merge in this central midline structure. And I have lifted it up here. This midline central structure is called the linea alba. Linea alba, as the term implies, it's a white line. And this is a very tough structure. It contains crisscrossing fibers from the external oblique muscle of one side to the deep fibers of the external oblique of the opposite side and vice versa. And it also contains crisscrossing fibers from external oblique of one side to the internal oblique of the other side. And this crisscrossing fibers are referred to as the intramuscular interchange of fibers and intermuscular interchange of fibers. And because of all this crisscrossing of fibers, the linea alba constitutes a very strong, tough fibro structure which gives protection to the abdomen. Sometimes we can have a defect in the upper part of the linea alba, and that is known as dive adication of recti. And that can be demonstrated when we ask the patient to, on a live patient to lift up the head from the bed without using the hands. We can see a bulge and that is referred to as dive adication of recti. The umbilicus is a weakness in the linea alba through which the umbilical cord came out in fetal life. When the umbilical cord drops off, it forms a psychiatric. In children, in babies, it can be a site of an umbilical hernia, but 93% of them close by one year of age. It requires surgery only if it does not close after one year of age. In adults, we do not get umbilical hernia. Instead, we have what is known as a para-umbilical hernia where it is located on either one side or the other side of the umbilicus. And finally, to conclude, we can see, this is the inguinal canal on the left side, which can be a site of inguinal hernia. And we can see these fibers here, these are the conjoined tendon muscle fibers, which are composed of the fuse fibers of the internal oblique and the transverse abdominis. And we can see the spermatic cord is passing through the external ring. In this particular cadaver, we had some interesting situation. We can see some remnants of suture material here. They had done an extensive surgery in the lower part of the lenia alba. And they had implanted this structure that we can see here. This is a reservoir, which they had implanted in the left rectus sheath. And this is the place where it was located. And from this reservoir, we can see a pipe coming out. This tube is going inside the strotum. And we can see another pipe coming out from the strotum and it is coming and continuing to the corpora cavernosa. This is a three-piece inflatable pinile implant, which is used for erectile dysfunction. And because of this region, this whole lower portion was densely adherent and fibroids. And that's why we could not see many of the structures on the right side and we came to the left side. So these are the structures which I wanted to show to you in the abdominal wall, put it into the rectus sheath, the neurovascular structures and the rectus abdominis muscle. Thank you very much for watching. Dr. Sanju Sanyal signing out. David O is the camera person. If you have any questions or comments, please put them in the comments section below. Have a nice day.