okay so this is a tutorial on the muscles of the abdominal wall so I'm going to do this in two parts the first part will be on the muscles of the anterior abdominal wall and the second part will cover the muscles of the posterior abdominal wall so the muscles of the abdomen have several different functions they protect the viscera which of this soft organs contained in the abdominal cavity they assist in breathing so in inspiration these the abdominal muscles relax and allow the thoracic cavity to expand downwards and in exploration these muscles can contract and push the viscera upwards and also contraction of these muscles is useful in coughing and throwing up another function is to assist in defecation urination and giving birth and and these are assisted by increasing the intra-abdominal pressure so the pressure inside the abdominal cavity is increased by contraction of these muscles and this can help force things out of the body like urine feces and babies so in the anterior abdominal wall you've got five muscles and these are all innovated by anterior Valmeyer of spinal nerves t-72 l1 so you've got the rectus abdominus the pyramid Arliss the external oblique internal oblique and transversus abdominus so I'll just take you through these muscles now so first we've got this muscle here lying right in the midline and it's a paired muscle which is separated by this white line running down the middle so this white line is called the Linea Alba and this literally means white line in Latin and this this linear alva is formed by the aponeurosis of the various abdominal muscles so the lateral three muscles which I'll come on to talk about the external and internal obliques and the transversus abdominus form these flat tenderness sheets called aponeurosis which joined together in the midline forming this linear alba and this separates the two sides of the rectus abdominis muscle so I've just isolated the muscle and we'll take a look at the origin and insertion so the rectus abdominis muscle originates on the pubic symphysis and pubic tubercle and superiorly it inserts along the costal margin so the costal cartilages and also on the zippered process so you can see the zipper would process here so what this muscle does is it can flex the vertebral column and it's also involved in the other functions I mentioned at the start of this jutsu so a couple of other things to just point out so you can see another white line which lies on the edge of the rectus abdominis muscle on either side so this is called the linear semilunaris and then you can see these horizontal intersections which separate up the muscle bellies of the rectus abdominis so these are called tenderness intersections and these can be seen on people who have low body fat and a lot of muscle mass and the rectus abdominus so you can see in this picture and the sort of surface anatomy so you can see the linear Alba down the midline and you can visualize the tendinous intersections between the muscle bellies of the rectus abdominis so the second muscle which lies anteriorly in the abdominal wall is called the pyramid Allis muscle and this is a tiny little muscle and it isn't always present and it attaches to the pubis in fairly and in the midline it attaches to the Linea Alba and this muscle is innervated by the anterior ramus of t12 I love t12 so I've just switched over a diagram to show you this so what we're looking at is the left side at the left side so this left side spin sort of dissected away and you can see one half of the rectus abdominis muscle so the right side of the rectus abdominis muscle and just at the bottom so this is the the pubis here and in the middle you've got the Linea Alba so the pyramid Alice is this tiny little muscle here which attaches from the pubis to the Linea Alba so these two muscles the rectus abdominus and the pyramid Arliss muscle are actually enclosed in something called the rectus sheath and this is a tendinous sheath formed by the aponeurosis of the three lateral muscles which I'll come on to talk about next so the upper three-quarters of the rectus abdominis and me so this area I'm showing you here with the mass the upper three-quarters are fully enclosed by this rectus sheath whereas the bottom quarter is actually so only the anterior surface is covered by the rectus sheath so what I'm going to do now is I'm going to switch over to a cross section to show you this rectus sheath so we're now looking at a cross section and this is anterior so you've got the rectus muscle so both half of the rectus muscles and in the middle you've got the linear Alba and then laterally you've got the three muscles lateral muscles which I'm haven't talked to you about yet but just briefly you've got the outer muscle called the external oblique the muscle below that's called the internal oblique and that most inner muscle is called the transversus abdominus so as you can see these muscles form this flat tendon which is known as an app in your oasis so these the aponeurosis of these three muscles enclose the the rectus abdominis muscle in what is called the rectus sheath and these aponeurosis meet at the midline to form the Linea Alba so this is a cross-section taken from the upper three quarters so you can see how both surfaces of the rectus abdominus are enclosed so the anterior surface is covered and so is the posterior surface and you can see how the internal oblique splits so it passes anterior and posterior behind the rectus abdominus so this next picture I'm showing you is from the lower quarter so the bottom quarter of the rectus abdominis muscle and you can see that this sheath is a slightly different because it doesn't go behind the rectus abdominis muscle so all three aponeurosis pass in front along the anterior surface of the rectus abdominis muscle so next we've got the muscles which sit laterally so you know what these are there's three muscles the external oblique internal oblique and transversus abdominus from a superficial to deep so first is this muscle here the external oblique so this muscle originates on ribs 5 to 12 which you can see here and it inserts in fairly on the pubic these are the iliac crest the pubic crest and pubic tubercle in this area here and it inserts sort of in the midline on the Linea Alba and also on the zippered process up here so you can see how this muscle forms this flat tendon which is called an aponeurosis and you saw how this aponeurosis surrounded the rectus abdominis muscles to form the to form part of the rectus sheath so the external oblique on either side joins together in the midline fuses to form the Linea Alba which I showed you earlier so if both muscles contract it can flex the trunk but if one one one side contracts it can laterally flex the trunk so it can flex the jump to the same side so the fibers of the external oblique pass info immediately so they've passed downwards and towards the midline in this direction so if it just removed the external oblique we've got the internal oblique which lies below it so these fibers passed in the in the other direction so they pass superiorly and medially so one way of remembering the direction that the fibers are oriented is to use the mnemonic hands in pockets hands on tits so how does this help you remember so if your hands are in your pocket so imagine your hands kind of like this so pockets has to let it be in it for external oblique so the direction you're sort of forearm is it's the direction of fibers so in this direction so for the external oblique you've got your hands in pockets pockets as an e external oblique so the fibers are in the info and medial direction so hands on tits so for being crude but that's the mnemonic so hands on tips so they're up in that direction so the fibers pass superiorly and medially so tits has an eye in it so internal oblique so the fibers are super Oh medial so so just going back to the external oblique muscle there's one important thing I forgot to tell you about so the bottom part the inferior margin of the aponeurosis of the external oblique muscle actually forms the inguinal ligament so I've just isolated it here and you can see the bottom part of the up and your ice is forming this ligament which runs from the anterior superior iliac spine here down to the pubic tubercle so that's important to remember so just going back to the internal oblique and you now know which direction the fibers pass so the internal oblique muscle and originates on the iliac crest and also on the lateral part of the inguinal ligament and it inserts on the lower ribs so you can see these ribs 10 to 12 on bottom four ribs nine to twelve and it also inserts in the midline on the linear alba so it joins the app and other fnu aces as you know and it also inserts on the pubic crest here so it's not the aponeurosis isn't shown here but you know that it extends into the midline and joins the Linea up so similar to the external oblique when both of the internal oblique contract it and flexus the chunk so it brings the chunk like this and if one side one muscle contracts it laterally flex the trunk so now brings the trunk to the same side so the last muscle we've got is the transversus abdominus muscle so if I just remove the internal oblique we've got this muscle that sits underneath it and it's called the transversus abdominus muscle because the fibers are oriented transversely so horizontally so like this so let's just take a look at the origin so it originates on the iliac crest so you can see that here and also on a lateral sort of parts of the inguinal ligament and then it has so and also that you can see the origin at the top on the costal cartilages and then again it inserts on the Linea Alba and inferiorly it inserts on the pubic crest so you can see it's attachments here so iliac crest england ligaments gone but it attaches on the lateral parts of the england ligament over here it attaches on the costal margin and it attaches in the midline at their Linea Alba and also inferior at the pubic crest so those are the muscles of the anterior abdominal wall it's pretty easy you just got five to remember so you've got two which sit until you've got the large rectus abdominis and you've got the tiny little period pyramid Ollis and then you've got the three lateral muscles so the external and internal oblique muscles and the transversus abdominus muscle