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Ok, so hello everyone. Um Thank you very much for signing up for uh the second part of our teaching series. Um I appreciate you taking the taking the time. Um So this week we are going through the abdominal wall and trying to kind of gauge what the clinical relevance of that is for exams. And for this session, we have Chris Archer. He is 1/4 year medical student will be taking us tonight and Chris uh recently got his master's in clinical anatomy. Uh He did a plastics project and he did very well. Um So you are in good hands. So, uh hopefully you enjoy tonight's presentation and uh I'll be on the chart if there's any questions. OK, I'll hand you over to us. Thanks. Thanks James. So like James said, I'm just going to follow up on his lecture from last week on the thoracic wall focusing now on the abdominal wall, um particularly the clinical evidence of it. So just a quick overview of what we'll be covering, we'll be looking at common incisions made on the abdomen to get access to the relevant organ systems, the various layers of the an interlateral abdominal wall, focusing on the musculature and detachments actions and innervation. And also looking at the components of the rectus sheath briefly as well, the posterior abdominal wall, the neurovasculature supply and then also spending a bit of time on the inguinal canal before moving on to some clinical correlates, primarily herniation. There are various types of abdominal hernias as well as CPI medusa before doing some MC Qs at the end. So if you have any questions throughout, just pop them in the chat and James will keep a look at the chat and we'll answer anything at the end. So just to begin with, you can see on this side, you've got the relevant organ systems within the abdomen. And then on the right, you've got the various incisions that are made to gain access to them. So we'll begin with a cocker incision, which is a subcostal incision and it's usually performed to gain access to the gallbladder for an open lap cholecystectomy and then moving across, you'll see a paramedian incision. Now, the paramedian incision is usually performed to gain access to organs at the side of the abdomen. So you've got your spleen, your adrenal glands, your kidneys and then transverse and a midline incision. They tend to be more in the acute setting for emergencies where the surgeon has to gain rapid access to the abdomen. So that might be because he needs access to the abdominal aorta, um or maybe some bowel perforations then moving down to the right here, you've got mcburney's incision and the lance incision. And both of these are both, both of these are used to get access to the appendix for an appendectomy. So you can see how it corresponds to the location of mcburney's point. So mcburney's point is a point on the abdomen that is two thirds the distance from the umbilicus to the anterior superior iliac spine and it corresponds to the base of the appendix. We also have a fun style incision which is performed for a cesarean section and it can actually be quite hard to see this because this incision now is made just in line with like the natural lines of cleavage of the skin. So the natural skin folds that women can get after pregnancy. So if you're doing an abdominal examination in hospital or anything like that, make sure if you've got any skin folds to lift them up and have a look underneath. Uh Richard Morrison incision is typically performed for a renal transplant. So it is uh just allowing access into the flank here. And then a battle incision can also be used to allow access to the likes of the bile and then any underlying organs as well or any vessels beneath it. We're now just gonna look at the various layers of the an interlateral abdominal wall. So going from superficial to deep, the first layer we get to is skin which is gonna be your epidermis and your dermis. And then following that, you have subcutaneous tissue and the subcutaneous fatty tissue is actually composed really of two layers. So the more superficial layer is camper fascia, which is quite fatty. And then beneath it, you have a more bam membranous layer and this is called scarpers fascia. But the two of them together make up one layer of subcutaneous fat. And then going beneath that you have investing fascia of the three underlying muscles. So the first muscle we come to is external oblique. Following that, then you'll have underlying fascia of internal oblique and then the internal oblique muscle. Again, another layer of fascia between the muscles before we get to transversus abdominis. And then following that, you'll have the transversalis fascia followed, then by some extraperitoneal fat and then finally, and the parietal peritoneum. And at that point, then you're in the abdominal cavity and if any of your medical students are in hospital. Um and theater, this is a common question that surgeons like to ask if they're doing any incisions. They like to ask, you know, name the layers of the abdominal wall we're cutting through. I actually got a it last week. So that's a could be simple question if you know your stuff. So now I just look a bit closer at the musculature of the abdominal wall. So again, going from superficial to deep, we start off with external oblique and this originates from the lower aspect of the lower eight ribs and it attaches to the xiphoid process. The linea alba, which is this midline down here, this is a, a fascial line down the middle, the pubic crest pubic tubercle and iliac crest. And you can see in this diagram down here that it is the rolled up portion of external like at the bottom that forms the inguinal ligament. So this ligament just runs from the anterior superior iliac spine to the pubic tubercle. And a way to remember and identify this muscle is the orientation of muscle fibers. So it, it's typically called the hands and pockets muscle because if you look over here, it corresponds to the patient's left. If you were to put your hands in your pockets, your hands would be going down like that, your fingers would be like that. And whenever you apply that to the abdominal wall, that's the way that the muscle fibers run and then going beneath that, we have internal oblique and this or originates from the lumbar fascia, iliac crest and the lateral two thirds of the inguinal ligament, uh it runs perpendicular to external oblique. So, external oblique is hands and pockets and an internal oblique is at right angles to that. And that attaches to the lower three ribs, the costal cartilages, the xiphoid process, the linea alba and the synthesis pubis going a bit deeper. We have transversus abdominis and this goes from the lower sixth costal cartilages. The lumbar fascia, iliac crest, and then the lateral third of the inguinal ligament to the zip process. And it's in the name Transversus, it runs transverse, so horizontal and it goes to the zip process, the line alba and symphysis pubis deep to that. Then we have rectus abdominis and this attaches to the symphysis pubis and the pubic crest and then runs up to the 5th, 6th and 7th costal cartilages. And this is a void process and that is just a vertical muscle fibers in terms of the actions of these muscles. So the external and internal oblique muscles help compress the abdominal contents. They also assist in the flexion and the rotation of the trunk. And they also help in forced aspiration, micturation and defecation. Because when you think of whenever you are doing forced aspiration, whenever these muscles contract, they force the abdominal contents up against the diaphragm, helping you to expire. The transverse abdominis really only acts as well to compress the abdominal contents. And then the last one, rectus abdominis does also compress the abdominal contents, but it also helps flex the vertebral column. And it's an accessory muscle of aspiration. We're just now going to discuss the rectus sheath. Now, the rectus sheath is formed by the aponeurosis of external and internal obliques as well as transverse abdominis and it has two walls, an anterior wall and a posterior wall. And it basically encloses the rectus abdominis muscle as well as the pyramidalis muscle. This is a small muscle that's often absent. Uh Its attachments are primarily the symptom of pubis and pubic crest to the linear alba. Uh It also contains the anterior remi of the lower six thoracic nerves, the superior and inferior epigastric vessels and also various lymph vessels. So as we can see in this image, that is the anterior layer of the rectus sheath, peeled back. And then we can see various uh intercostal nerves. And on the next slide here, we can see the various composition of the walls as we go down the abdomen because the composition of the rectus sheath changes at three main levels. So above the costal margin, the anterior wall is formed by the aponeurosis of external oblique only and the posterior wall is the fifth to seventh costal cartilages and the intercostal spaces. And then we're gonna go from the costal margin to the arcuate line. Now, the arcuate line is a point which is about halfway between your umbilicus and your symphysis pubis. Here, the internal oblique muscle actually splits in two. So you have the posterior wall of the internal, of posterior lamina of internal bleak wrapping around behind the rectus abdominis forming the posterior wall of the rectus sheath along with the transverse abdominis. And then anteriorly, we have the anterior lamina of internal oblique as well as an external oblique form in front. And then you also have the various layers of the skin and some subcutaneous tissue in front as well from the arcuate line, then to the symphysis pubis. So, from about halfway below the umbilicus to the symphysis pubis, the aponeurosis of all three muscles. So, external oblique, internal oblique, um as well as transversus abdominis, they all then just are present in front of rectus abdominis. So the rectus abdominis muscle then lies directly onto the transversalis fascia. So there is no posterior wall. Now, I just uh briefly look at the posterior abdominal wall. So this wall is formed by the lumbar vertebrae, the discs and three main muscles. So we have soas major and soas minor. Now, so minor tends to be a, can be absent in a significant proportion of people, but the so major is rather than normal and it, it or from the trans process of T 12 down to L5 and it at to the lesser tranter of the femur. And so it minor is then from the transverse processes of T 12 and L1 and joins onto the less lesser tranter of the femur with. So major, Iliacus is in quite a wide fanshaped muscle that originates in the iliac fossa and goes from the iliac crest and also insert onto the lesser tranter of the femur. So because all of these muscles converge into one tendon and attach to the same point, you'll often hear them referred to as one called the iliopsoas muscle. And the main action of this muscle is to flex the thigh onto the trunk or if you're standing with your feet planted, it can help flex your trunk forward in the direction of landing it onto your thigh. So if you're trying to bend over to touch your toes, for example, we also have then quadratus lumborum. So this muscle attaches to the inferior aspect of the 12th rib and the transverse processes of the lumbar vertebrae down to L5 and it attaches to the iliac crest and it primarily is a muscle of accessory expiration and it fixes 12th rib during inspiration and depresses it during forced expiration. Now, it can also help laterally flux the vertebral column. So if you're going side to side, it'll contract unilaterally in terms of the neurovascular supply. So the abdominal wall is supplied by somatic innervation. So, somatic innervation is where the brain receives sensory input that is sharp, intense and it can be well localized and it is innervated by the lower sixth thoracic nerves and the first lumbar nerve which is then divided into the iliohypogastric and ilioinguinal nerves. So, as you can see in this diagram, you've got the various dermatomes. I mean, you get to the abdominal wall, it goes down from T six to T 12. And you can see it's the anterior cutaneous branches as well as the li cutaneous branches of these nerves. And then you also have the divisions of the first lumbar nerve, ileo hypogastric and ileo inguinal. Now, the posterior wall is innervated by the Antero i of lumbar nerves, L1 to L3, 4. So it major and then the anti of subcostal nerve as well as L1 to L4 4 quadratus from borum and iliacus is only innervated by the femoral nerve. So that's L1 and I am moving on to the arterial supply. So the arterial supply is a bit different if you're above the umbilicus compared to below the umbilicus. So above the level of the umbilicus, the main arterial supply is gonna be via the posterior intercostal arteries 10 to 11 on the subcostal artery which branch from the thoracic aorta, the lumbar arteries 1 to 4 as well as the inferior phrenic arteries which arise also from the aorta, but just on the ab the abdominal aspect. And then you also have superior and superior epigastric and musculophrenic. So you can see in this diagram, superior epigastric and then you can also see musculophrenic over here and they are branches of the internal thoracic artery just as it descends parallel to the sternum. And then you have the inferior epigastric and the deep circumflex iliac arteries. So you can see over here if inferior epigastric and deep circ circumflex and then below the umbilicus, the main artery supply as a femoral artery. Now it by the divisions. So it's gonna be the superficial epigastric, superficial circumflex, iliac and the superficial external pental arteries. So an easy way to remember this is, that's the three superficial branches of the femoral artery. So, superficial epigastric, superficial circumflex, iliac and superficial, external pudendal. In terms of the venous drainage, there's a network of veins that radiate from the lycus. So these are drained then above into the axillary vein via the lateral thoracic vein and then they're also drained below via the superficial epigastric vein into the great saphenous vein. Now, there's important uh anastomotic network between the para paraumbilical veins. Um So that's clinically important if you have things like portal hypertension. In which case, these veins, the pa paraumbilical veins can become quite distended and engorge with blood. So we'll look a bit at that later on, we're just gonna focus for a wee bit now on the inguinal canal. So, the inguinal canal is an oblique passage that goes through the anterior lateral abdominal wall in the lower quadrants and it runs parallel and just superior to the inguinal ligament. And it's about four centimeters long and it goes from an opening in the transversalis fascia called the deep inguinal ring, um which is just above the midpoint of the inguinal ligament. So, the midpoint of the inguinal ligament is gonna be halfway between the anterior superior iliac spine and the pubic tubercle. So you can see here, you have the deep inguinal ring halfway between and then it runs to the superficial inguinal ring, which is an opening and external oblique aponeurosis. And that is just superior to the pubic tubercle. So in terms of the boundaries of this canal anteriorly, you have the aponeurosis of external oblique and then this is reinforced laterally by internal oblique, posteriorly. You only have transversalis fascia at the back. The roof is gonna be formed by the lowest arching fibers of internal bleak transversus abdominis and also transversalis fascia. And then the floor as was previously mentioned is only the inguinal ligament. So in this diagram, you can see that the inguinal ligament just runs inferiorly to the canal and you might be able to appreciate now, the contents and the various structures within the inguinal canal. So the contents are the spermatic cord in males, the round ligament in females, the ilioinguinal nerve in both and the genital branch of the genital femoral nerve. So, as we can see here, you have the deep inguinal ring going down the superficial inguinal ring and then you have the various contents. So in this case, it's a meal and you have the spermatic cord and it's various contents as well. And then you can also see does it show the little inguinal nerves? Unfortunately, they're not be able to miss diagram. There's also, there's also a really important triangle called the inguinal triangle or it used to be called the Hesselbach triangle. So if you're in for any inguinal hernia repairs, this is a common area that surgeons like to ask the boundaries of. So medially, you have the lateral border of rectus abdominis laterally, you know, the inferior epigastric vessels. And then for the floor or inferiorly, you have the inguinal ligament and then this is the inguinal triangle. And they like to ask about this area because there's an area of weakness in the abdominal wall, um which can allow hernias to protrude through. So now just to talk a bit more about herniation. So, herniation is the protrusion of abdominal viscera through an area of weakness or a defectiveness in the abdominal wall. And this can happen at various locations. So you can have epigastric, which is gonna be in the midline. It's gonna be above the umbilicus in the upper abdomen. You can have incisional, you can have really incisional hernias anywhere really. Um As long as it's at the site of a previous surgery. And that's where basically the tissue hasn't fully healed. And there's been a bit of a weakness left there, allowing the abdominal contents just to push through. You're gonna have an umbilical hernia and this is just gonna be at the navel. And you can see these often in, in Children, especially if they've been born premature. Uh It's a result basically of the linea alba. So that fascia that runs in the midline from not completely fusing. And then you've got a bit of a gap and then you've got a wee umbilical hernia protruding through and then you have your three types of inguinal hernias. So you have a direct inguinal hernia and then you have an indirect ankle hernia. So we'll talk about them on the next slide. But both of these hernias can present in the lower quadrant. And they can also be just above the pubic. They tend to be and then laterally to the anal canal. You can have a femoral hernia. I'm not gonna talk about that too much because it's not really part of the abdominal wall lecture. Um But it's just important differentiation that femoral hernias occur more lateral than inguinal hernias. In terms of the presentations, patients often present with a painless lump that may protrude whenever they cough or if they strain so upon defecation or anything like that or if they sneeze or anything like anything that increases intraabdominal pressure, they may find that the lump then protrudes. Um Now some patients may describe being able just to push it back in and it it goes in. So that's just called reducing the hernia. Um Other patients, they may not be able to push it back in, it may just stay out. So in terms of your investigations, um that's typically an ultrasound scan or CT scan just so we can actually see the contents of that bulge. So in this case for hernias, it tends to be small bile and it's worth remembering that irreducible hernias. So hernias that can't be pushed back in, they represent a greater risk for strangulation, which is basically in this image, you can see how it can be pushed back in and you have restriction then of the arterial supply. And that's basically because you have a very small opening, a very small area of weakness in the abdominal wall. A little bit of bile has managed to squeeze through, but then it squeezed through, but it won't be able to be pushed back because it's so narrow. And then the arterial supply gets, it gets cut off and then you can start to have this ischemia and then necrosis and it can become gangrenous. So for that reason, strangulation is actually a medical emergency. And in terms of symptoms, the patient usually presents with sudden severe pain and also symptoms of bowel obstruction. So they may have vomiting or constipation and nausea as well. Even if they're not vomiting, they may feel like they're going to vomit and it requires immediate surgery to, to relieve the hernia because otherwise you're at risk then that you're gonna need a laparotomy and you might need some small bowel resection as well. And the most common type of abdominal hernias is inguinal hernias and they make up about 75% of all abdominal hernias. And they can be split into two categories, direct and indirect. So it sometimes it's actually quite easier to go back to the basics. So anatomical diagrams can be great, but sometimes a simple drawing can actually just explain a lot more. So an indirect hernia, indirect inguinal hernia is where you have protrusion of the bile through the entirety of the inguinal canal. So it protrudes through the deep inguinal ring the whole way along and then it exits through a superficial inguinal ring. So it follows the path of the testes that whenever they de during the descent through the processus vaginalis. Now, the processus vaginalis as an embryological structure. And it's basically an opening in the peritoneum that follows the path of the inguinal canal. Um and the mass of the hernia is actually within the spermatic cord. Whenever you think of the contents of the, of the anal canal in males, at least it'll be within the spermatic cord and then it protrudes down and is often found in the scrotum or in females in the labia. And it's important as well to recognize that the la the, the mass is actually lateral to the inferior epigastric artery. And it is most common in males and it's about 20 times more common in males compared to females. When we compare that to a direct inguinal hernia, this hernia doesn't go through the entirety of the inguinal canal. It will only protrude through the posterior wall of it and enter it after the deep inguinal ring. So you can see in this diagram, it's protruded through the posterior wall of the inguinal canal passed down adjacent, then if it's in a male, it's adjacent, then to this proma cord and it exits to the superficial inguinal ring. And these hernias rarely protrude far down into the scrotum or the labia. And the mass is medial to the inferior epigastric artery compared to lateral and indirect. Another clinical correlate, then we have is CPI medusa. Um So as I mentioned, this is a clinical sign showing indicative rather of portal hypertension. So it's distention of the superficial veins around the umbilicus and the paraumbilical veins and these veins ANAs tomo stent with the portal vein. And if there's any obstruction that results in portal hypertension, there's a backflow of the venous blood and the veins become engorged and distended and you get this clinical picture then so and as you can probably tell from the name cap medusa because you can see it more in this diagram, maybe medusa had snakes for her and they kind of spread out from her head. So in this image, you can appreciate the umbellus, you have the veins distending around it. Uh The most common cause of it is liver cirrhosis, but you have a few other causes. So you have Baueri syndrome and the most common cause worldwide is actually also schizos. Uh It's a, it's actually a type of parasitic worm that can infiltrate if you've been bathing a any water or anything. It actually contaminates the water from snails and then it can enter through any opening. Uh It tends to be actually through the urethra and then it can go up and then it can lay eggs and then whenever like, like, yeah, it's quite a nasty condition but it's important to recognize then that worldwide, especially in the likes of Africa and maybe in the Caribbean as well. If you're in contaminated water and they come back and they've jaundice and signs maybe of liver cir of liver cirrhosis, but it's not liver cirrhosis, it's schisis. And you will see this kind of a picture where the vein is so distended. I know you finish quite early, but we have a few M CQ questions queued up. So if James wouldn't mind answering the questions, they start off quite easy, I'll say, and then they get a bit harder as well just to see if you've been paying attention. But thank you very much for joining. Um And if you have any feedback, please share it in the wee form that will be sent out following the lecture. Uh Thank you very much. I'll just ask James actually. Have there been any questions in the chart while I've been presenting? Uh No, no questions. Do you want? What questions do you want me to start with first? Sorry. Oh, just the first one cued up. That'll do uh a sure. Actually, the order will go now in reverse, they might start harder and become easier. OK. So um for this question, then uh we have 20% for the labs incision, 0% for, for Morrison. Um 20% for transverse incision called Murs point. Then uh 28% for mcburney's incision and then 42% for the lungs, incision, transversely crossing uh the 0.2 3rd away from the, to the right uh anterior sp I'll explain. Yes. So it'll be the last incision going from two thirds of the way from the umbilicus to the right AIS. So mcburney's point will always be further from the umbellus compared to the ASIS. It's always closer to the ASIS. So if you put out, congratulations, OK. Um I'll do the next one now to a patient presents with a painless ping mass in his right inguinal region. When you apply pressure to it, the mass reduces. However, when the deep inguinal ring is covered and the patient is told to cough, the mass reappears. What is the best description of this hernia? So, direct inguinal uh paraly and direct inguinal uh femoral or epigastric. Got. So for this one, then we have 71% for direct inguinal hernia and we have 28% for indirect. OK. Well, that's what we are black. OK. So I think the majority there got it right. So it's gonna be a direct hernia because if you apply pressure to the deep ring, you an in an indirect hernia because it protrudes the whole way along from the deep ring to the superficial ring. If you cover it from the deep, it won't be able to protrude because your hand is there. But if it's a direct hernia it doesn't enter through the deep inguinal ring, it'll enter after it so then it can reappear. Yeah. OK. So, um next question, then, so if a surgeon is performing a left paramedian incision below the arcuate line, what is the last layer uh which they will cut through before reaching the transversalis fascia? So the fascia of external oblique, the rectus abdominis muscle, the external oblique muscle, the fascia of internal oblique and the, or the transversus abdominis muscle. Let's go one more time for a few more responses. Um OK. So we have 33% for the rectus abdominis muscle. We have 66% for the transversus abdominis muscle. Ok. So the correct answer is gonna be the second option. So it's Rectus abdominis muscle. So I actually just go back to that slide. So the main thing in this question, it's not even about the incision or anything like that. It's below the arcuate line and below the arcuate line, it's gonna be the Rectus abdominis muscle because it lies directly on the transversalis fascia. So you have really no posterior wall to the rectus sheath cause all muscles will be in front and then it's directly in contact with the transversalis fascia. So, as you can see here, all the muscles, all the muscle fibers attach anteriorly and then you have the rectus abdominis and then posterior to that, you have the transversalis fascia. OK. Thank you. So, uh last question. Now, um I'll start four. So, a surgeon is performing a laparoscopic repair of an inguinal hernia and asks you what the arterial supply of the surgeon is anterior sponge vessels. So, uh first one is the subcostal artery, lumbar arteries, 14 or an inferior external IAC. The next option is the superficial epigastric, superficial, external pedal and the deep circumflex iliac arteries. The next option is the abdominal aorta, external iliac artery and femoral artery. The option after that is a superficial epigastric, superficial circuplex, iliac and superficial uh external pental arteries. And then the last option then is our superficial epigastric, superficial, external iliac and superficial internal pedal arteries. Ok. So we'll give it another minute for responses. Another a few seconds. Ok. Oh uh The majority of went with the superficial epigastric, superficial circumflex iliac and the superficial external pedal artery. So that's 71%. Yeah. So I'll just bring that up for anybody who didn't get that right. So it's gonna be II said I was a bit mean with this question because I did say it's the three superficial branches of the femoral artery. But you can't always just go by the first word in answers. So when you look at the last one, it's superficial, internal pudendal instead of external pudendal and it's also superficial circumflex iliac instead of external iliac, which is kind of the main giveaway because I think at that point, I was just throwing a few random made up branches in just to see, try to maybe trick a few people out. But no, it's good to see the majority of people then. Uh I got that right. Yeah. So thank you very much Chris for taking the abdominal wall xer. That was really good and very comprehensive but concise. So I'm gonna share the feedback form uh for everyone here. So we'd appreciate if you could take the time just to fill aside. Um It provides feedback, not only for Chris, but for the society. So this is when they are and la we're still trying to find your fate and uh hopefully this has been useful for you and it'll be used for exams. Um But once again, thank you very much for uh turning up. We really appreciate you taking the time and next week we will be having a uh kind of short lecture on the brachial taxus and that will be taken by Alex. Um who is really good. She's gonna master in like a on me as well. But uh thank you very much Chris. No problem. Um We'll hang about for a bit here guys if you've got any questions, uh if not just call out the feedback form and then head on um the slides and recording will be made available over the next few days. And if you keep an eye then on our Instagram account, um you'll see the like to the next session. But thank you and have a nice Night.