Abdominal wall muscles (anterolateral) anatomy

[Music] okay we're going to look at the anatomy of the muscles of the abdominal wall or more accurately the muscles of the anti anterior and lateral abdominal walls because we've got this whole thing this whole trunk this whole tube thing going on here and the muscles of the back are something else if i remember maybe we'll look at the muscles of the posterior abdominal wall if i haven't looked at those before next week and we might also lump them together and say the anterolate abdominal wall because we have layers of muscle here and we need to think about why we have layers of muscle here what they do it's more than just movements and more than just your six pack and really if we look at where they run from and where they run to like any muscle but also how they overlap and work together we'll get a better understanding of how this functions as a unit which is really important functionally and when problems occur all right something like that tried to pick a time of day where the kids had gone home i failed [Music] this person does not have any abdominal wall muscles but will be very useful in showing us where they attach but this person does and we can see some of the layers here but the skeleton does show us something pretty important right we have a rib cage here so we have a body wall we have a pelvis down here and we have nothing nothing in between the two and yet you know that we have a lot of abdominal viscera we have the gastrointestinal tract and lots of organs all sorts of things in here that we need to keep in here so that then is a major function of the muscles of the anterolateral abdominal walls is to form a wall to be a wall to hold all this stuff in place and protect it and when that wall breaks down that's when the inside bits start to get out we have various opposing pressures here so that's another function of these muscles is we can we can increase the pressure inside the abdomen the abdomen and the thorax are linked and yet separated by the diaphragm the diaphragm can move up and down so you can change pressures in your abdomen and affect the pressure in your thorax i'm doing it right now what happens to your abdominal muscles when you cough sneeze if you haven't noticed before pay attention next time if you raise the intra-abdominal pressure you can avoid things out of the abdomen during defecation uh maturation you know when you when when you contract to empty the bladder well the detrusor muscle of the bladder that's under autonomic control you can't you're not actually con contracting that you're contracting the muscles of your abdominal wall to increase the pressure in your abdomen abdomen which pushes down on the bladder in the pelvis and pushes the urine out of the bladder things like that vomiting as well pushing things out from the stomach up the esophagus that's intra-abdominal pressure when you're lifting heavy things to support the trunk and the limbs that are attached to the trunk you you take a deep breath and you sometimes hold your breath um and you increase the abdominal pressure so you you know when you have a lot of pressure inside a tube that's a stronger tube than having a tube with no pressure in it then it's floppy um if you think about spacesuits they go rigid when the air inside them is against the vacuum on the outside the pressure difference is such that the tube goes rigid like a balloon same with our abdominal pressure raising so when you lift things you raise your intra-abdominal pressure you're using your abdominal muscles so you probably use them more than you realize and it's more important to keep the strength in these abdominal muscles than maybe you realize and if they're forming the wall then if they fail if they become weak then problems can follow so these are also functions of the muscles of the abdominal wall muscle is quite a good building material particularly if you match it with various connective tissues to hold it in place it makes a nice thick strong tough mobile thing that you can make various shapes out of so we're forming a tube we're forming a trunk to keep everything inside and protect it and also because we're vertebrates we like to move our vertebrae and the muscles of the abdominal walls take part in that in flexion of the trunk lateral flexion of the trunk rotation and things like that the other thing is is that these things um so we have the muscles of the abdominal wall and then we have muscles of the back those have all got to work together and be balanced for this this trunk system this muscular system of the trunk to function normally and then we have these great big things hanging off down here legs are the lower limb is a heavy powerful thing it has muscles running from here down to there so then the lower limbs are also hanging from the trunk so don't consider the muscles of the abdominal wall in isolation link them to the muscles and movements of the back the muscle movements of the lower limb and this will all make a lot more sense but it will be a lot more complex i'm afraid right now if we're going to think about the muscles we might as well think about all the other layers so that it makes more sense this is covered in skin we remove the skin we see a superficial fascia that's the fascia we see in most places in the body holding things together now um superior to the umbilicus we see superficial fascia like we do elsewhere in the body inferior to the umbilicus down here we see um a camper's fascia which is the more superficial layer and campus fascia is quite a fatty fascia so you may well find i certainly do that there's kind of like a band of fat here um and it is it's like a band it's like a waistline of fat and that's because the canvas fascia is very good at holding on to fat because fat is good fats are a reserve of energy fat keeps us warm so the camper's fascia is here and then the scarpa's fascia is a deeper layer maybe a bit denser still not very thick but pretty dense and that's continuous with the fascia of the lower limbs the fascia lata is continuous with the fascia of the perineum the collis fascia so that's something you might come across so we have to go through the campus fascia the scapus fascia to get to the muscles underneath ah but that still looks like we've got some fascia here it's not and that leads to the other issue we have here right this white line in the middle is the linear alba literally white line in latin romans when they were racing around the track they had a white line down the middle i think called the linear alba anyway so the linear alba is a key structural thing here for us when we're considering all of these muscles and what we're actually seeing here is something quite special which we'll come back to later okay so if i twist you that away this is the most superficial layer of muscle this is the external oblique muscle layer the external oblique muscle there can you see the fibers are running in this direction it's it's running from the ribs so we've got serratus anterior and some other muscles up here which it really kind of tightly interdigitates with but it's running from it's running from um the anterior surfaces of ribs 5 to 12. remember 11 and 12 of these floating guys around here right but it's running from the ribs around to the linear alba that white line which is now not here to the pubic tubercle down here and this is the iliac crest to the anterior half of the iliac crest so it's running it's running around here going down here and attaching to here so between these two bony points we have the inguinal ligament which yeah which is a good attachment anyway so we have external oblique coming around here but if i said that the external oblique muscle layer runs to the linear alba how does that work it doesn't look like it's running to the linear album and it looks like it's running this far how does it get over there then right well we'll come back to that so that's the external oblique muscle there fiber's running in this direction so anteriorly and inferiorly generally not entirely but generally running in this direction now if we take that muscle layer off we can see the next muscle layer this is the internal oblique muscle the the fibers of the internal oblique muscle are running in the opposite direction 90 degrees to the external oblique fibers over the top they're running anteriorly and superiorly and they're also running from the anterior half of the iliac crest and they're running up to these ribs here but they're running up to the costal carthages they're also running to the linear alba but again we don't see them running to the linear alba so how do they get there no oh back here there is a significant fascia connective tissue sheet tied into a number of things back here it's called the thoracic lumbar fascia it's kind of like a diamond shaped fascia which lots of things attached to and if lots of things attached to it then they in turn attach to one another now the internal oblique muscle is also coming from the thoracic lumbar fascia around here so it's properly wrapping around and then it runs up to ribs 10 to 12. see we're seeing these ribs here 10 to 12 and it will also connect it also insert into the um into the pubis bone through the conjoined tendon something we're going to come back to later because we need to add a bit more anatomy before we can describe the conjoint tendon so most of the fibers are running in this direction but not entirely that's the internal oblique muscle layer the third layer the deeper layer is the transversus abdominis i think i'm going to have to dissect oh he's lost a lung so the deepest layer we can see running around so these fibers are running transversely we can kind of see the three layers there external oblique internal oblique transversus abdominis so this is the transversus abdominis layer running around like this and again it's running to the linear alba so again the thoracic the transversus abdominis muscle is also wrapping around from the frasso lumber fascia it's going to attach we can't see here but to the the costal cartilages of ribs what seven to twelve and again is going to also attach to the anterior iliac crest and run all the way around to the linear alba and to some other connective tissues as well but you get the gist we've got three layers of muscle some some fibers running in that direction some fibers running in that direction some fibers running around in that direction if you were trying to make a wall out of tape and hold something inside would you build it like that seems pretty sensible right and we see the same organization in the intercostal muscles between the ribs you know suggesting this is this is like a segmental tube animals thing right so again in the intercostal muscles we see three layers of muscle we see different directions of fibers as well because we're forming a body wall while we're talking about the intercostal um stuff these muscles are innervated by the nerves running around the body wall which are the intercostal nerves running around here innervating these muscles from about you know t7 to t11 because the one at t12 gets called the subcostal nerve because it's sub the ribs it's under the ribs and then we have the ilio inguinal and iliohypogastric nerves which come from the l1 level and they're going to curve around descend actually in between these layers of muscles so they innervate them as they go past as well so the muscles of the body wall are innervated by the nerves of the body wall sensible okay but what about the the main attraction then um the rectus abdominis muscles have become some strange indicator of you know modern health fitness attractiveness and there are two rectus abdominis muscles one on either side separated and joined by the white line the linear alba and then we have these tenderness bands these tenderness intersections running across transversely which then chunk this muscle up into bands giving the six-pack but i said that the campus fascia is a really good fascia for storing fat so to show off these muscles you need to get rid of a lot of body fat because kind of one of the last stores of body fat is here which means that you need to get a really low overall body fat percentage to get rid of the fat covering these muscles and then they don't have to be particularly big to see them you just have to be very lean but if they get larger from doing sit-ups or whatever exercises you like crunches and hanging leg raises and all the beauties then they will yeah they'll start they'll get thicker like any other muscle so rexus means straights we have these two straight muscles running from the xiphoid process and the costal cartilages down to the superior edge of the pubis bone the pubic crest the the pubic crest and the pubic symphysis here and then running up to the xiphoid process this is the most inferior part of the sternum here the xiphoid process and then these costal cartilages so they're forming an anterior band oh and there's another muscle that i always forget this is pyramidal it's only about 80 of people have have these there's one on either side it makes a triangle right so pyramidalis is anterior to um rectus abdominis but again it's running from the pubic crest and the pubic symphysis to the linear elbow it's kind of a bit of a reinforcement down here okay how's that those are the muscles of the anterolateral abdominal wall we have three layers of external oblique internal oblique and transversus abdominis laterally we have rectus abdominis anteriorly and we have the pyramidalis muscles as well which you know whatever um but i said that these muscles laterally insert into the linear album how can that happen if we can see rectus abdominis well we can see what's happening here so a muscle and these are flat muscles they can become flat tendons and a flat tendon or a flat tendonis sheet is an aponeurosis it's very connective tissue rather than contractile and what happens is the external oblique muscle becomes becomes in a polyneurosis here at the margin of the rectus abdominis muscle and that aponeurosis runs anteriorly to reach the linear alba and inserts into it and that's what we see here that's what this white shading is on this right side where we have the external oblique muscle it becomes an aponeurosis and continues over to the linear alba the internal oblique muscle when it reaches the margin of the rectus abdominis muscle becomes an aponeurosis splits into two and half of it passes anteriorly to rectus abdominis and half of it passes posteriorly to rectus abdominis so surrounding it and then the transversus abdominis muscle the deepest layer does the same thing but stays posterior so all of these muscles wrap around rectus abdominis to get to the linear alba now do you see how this is a functional unit all of these muscles are tied together layered over one another interact with one another so it's a bit daft um just training one muscle you need to train them all for this system to work together and you need to train the muscles of the back if you want to maintain strength or increase strength this stuff's all got to work together so you've got to balance it sure you can train each muscle in isolation but train each muscle in isolation now i talked about those layers and that's that's what happens generally but we have something down here called the arcuate line where those layers change a bit and that's covered in another video called the arcuate line probably by the way google's you know google they got quite good at search so if you want to find any topics and you're wondering whether i've covered them just put my name into youtube the search bit at the top and the topic you're interested in if i've done it it'll come up okay i said i'd tell you about the conjoint tendon the conjoined tendon is this this aponeurosis of the transverse abdominis muscle and the internal oblique muscle running down inferiorly to the the pubic crest and the superior pubic ramus that's this branch of the pubis extending up here so that's what we're seeing here so these deep upon neuroses are coming together blending it becomes more tender like so that's the conjoined tendon anchoring these muscles particularly transversus abdominis and interior oblique to the pubic crest and the superior pubic ramus that is the conjoint tendon um so in in the male we have the inguinal canal here which is connecting the contents of the scrotum with the ab well the pelvic inside the pelvis it goes through the body wall into the into the pelvis right the inguinal canal passes through these layers that we've talked about to connect the contents of the scrotum to the abdominal abdominopelvic cavity the conjoined tendon forms an important part of the posterior wall of that so if it's weakened that's a there's a risk of then forming a direct inguinal hernia inguinal canal that's covered in another video too all right final word for you today is a semi lunar line this lateral border of the rectus abdominis muscle there's kind of like a curved line here where the lateral muscles become an aponeurosis and form the rectus sheath which is what those aponeurosis what those connective tissues form around rectus abdominis this is the semilunar line here at the border where that change occurs okay so those are the muscles of the anterolateral abdominal wall they're very important in forming a tube keeping all of the abdominal and pelvic viscera inside important in supporting maintaining and sometimes increasing pressures inside the abdomen thorax pelvis and that sort of thing and of course in moving the trunk and you know you can exercise them in isolation you can consider them in isolation but then you should consider them all as a functional unit and how they all link together you know imagine if you made that tube of tape with just one layer and in one direction how would it fail how would it split how weak would it and you know you'd build it with multiple layers in multiple directions right so train those multiple layers in multiple directions stay strong everybody it's the key it's the key right see you next week i'll check my list see if i've done posterior abdominal wall muscles if i haven't i'll try and remember to do that which means i'll probably forget between now and then and get distracted and talk about something else that i get interested [Music] you

Channel: Sam Webster

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Id: vZQTtRrDFmY

Length: 22min 31sec (1351 seconds)

Published: Fri Nov 26 2021