 So, today we are going to conduct a cat dissection, and really this is to isolate the muscles in the cat. So, in order to do this, there's certain equipment that is needed, first of all protective equipment, so that includes lab coat, gloves, goggles. The fixative that's used to preserve these cats is toxic, and so having an area that is ventilated and having that eye protection and skin protection is also very important. In terms of physical equipment, obviously the cat tray, where the cat is going to be laying, the utensils that will be used will be a blunt tipped large forceps, a probe, again blunt tipped scissors, as well as a scalpel. So, in dissecting the cat, you can notice that the skin has already been removed from the cat. So, at this level, we're looking at the remaining connective tissue, and we can even begin to see some underlying muscular tissue. So, in order to really isolate the muscles, it's important to remove that connective tissue. And so the connective tissue that is really important to get rid of is the loose connective tissue, and in particular the adipose tissue, which is the fat, as well as the areolar connective tissue, which is a loose connective tissue that is important in nourishing the skin, because it's highly vascular, it has lots of blood vessels, and that is important because epithelial tissue does not have its own blood supply. So, in removing this connective tissue, one of the techniques is instead of pinching perpendicular to the surface of the cat, I use the technique where I pinch on using the side of the forceps and moving in the direction of the tissue so as to remove it. So, I'm really just going to start from an area where there seems to be a lot of connective tissue and then proceed working from the anterior down to the posterior. I'll start on the ventral side and then work my way to the dorsal side. So, just as an example of what this tissue looks like, if I can get a close-up, you can see right here in the back, there is adipose tissue and it's a yellow tissue and it's just fat, and so that is something that has to be removed and it looks like this cat was not very fat, it was rather lean cat, so there's not very much adipose tissue, but what is there needs to be removed. And then the areolar tissue, I can point out later as it becomes a little bit more evident what that tissue is, but the goal of removing the tissue is to reveal the muscle fibers and so you can tell that the way that these muscle tissues is arranged is in fascicles and those fascicles are, they end up creating a striped pattern in the muscle and so that's the level that we want to remove the connective tissue. So as soon as you can see the striped pattern in that muscular tissue, then you can stop removing the connective tissue because if you go beyond that, you'll actually end up destroying the organization of the muscle itself and you'll lose some integrity in your muscle. So I'm just going to try to proceed and again working with the side of the forceps and just removing the connective tissue. You can see it comes off relatively easily, so I'm just working to remove this connective tissue and the thing with the loose connective tissue is that it doesn't take much to remove it. You see how easily that comes off and that's how you know you haven't gotten down to the muscular level, which is again another reason why I like to use the side of the forceps as opposed to grabbing like this because when I do that I've now got a hold of some muscle and I don't want that. So just continue to remove this connective tissue and actually we'll get to a point where you can really use your hands. So the hands is another, using your fingers is another way to safeguard against getting too much muscle. So we're just removing this very loose and I'm not having to exert very much strength at all to remove that and actually I've just revealed some areolar tissue. So if you zoom in into this area right here you can see that it's somewhat spiderwebby and there'll be another example of that when we get down to the legs, but that's what we want to remove. So as soon as you can see the striping of that muscle tissue that's how you know you've gone as far as you need to go. So what I'm going to do now is just for convenience actually use my blunt tip scissors and cut this areolar tissue off. Now you might mistake this areolar tissue for skin, but it's not skin. This is connective tissue, which is very different from epithelial tissue, which is what skin is. So connective tissue is laying over top, serving kind of as a boundary between the muscle and the skin and this is what we are going to remove. So in using the scissors what we want to do is hold whatever it is that we're trying to cut with the blunt tip forceps and then use our scissors to cut. We never want to grab whatever the tissue is with our fingers and cut because then we run the risk of cutting our gloves or cutting our fingers. So that's why we use our blunt tip forceps really as our fingers and so I'm just following along at the point of connection and the utility of the blunt tip scissors is that you can actually use it to clear it out, clear this tissue off and disconnect it from the muscle as opposed to if they were fine tip scissors you might end up poking into the muscle. But with the blunt tip because they're rounded it's not going to catch and so I can have a smoother cut. So this is areola tissue, this is what we're removing so as to reveal the muscle underneath. So I'm just going to continue to remove that tissue so as to clear out the chest area. So now that the catch chest is pretty much clean as upper chest and upper arms are clean of the connective tissue you can begin to see the muscle pattern and how it's striped. And so that was the level of removal that we wanted to have with our connective tissue. So the next step is to delineate the muscles or isolate the muscles from one group to the next. And so what you'll notice in order to do this you really have to pay attention to the orientation of the fibers. So muscles have a point of origin and a point of insertion and those are really the attachment points for the muscle. So if you look closely and follow the direction that those muscle fibers are going you can kind of see here that these muscle fibers are striping and they're running along the horizontal. Whereas if you move down you can see that the striping or those muscle fibers are arranged in a different orientation so no longer are they traveling along the horizontal they now when we move here they're now traveling more along an angle. And so at that line where that transition occurs from the orientation along the horizontal plane to more of a diagonal that's where that separation between one muscle and another muscle is. And so this boundary is where we want to make our cut. Never do we want to cut along the point of origin or insertion. It's always along the side of the muscle so parallel to the orientation of those fibers. So I'm going to take my scalpel now being careful because these are very sharp. And then I also want to use my forceps just as grip. Again never wanting to put my finger in the area of where I'm going to be using the scalpel. So I'm just going to very carefully in one smooth motion create a line that is going to separate just following along the normal separation between these two muscles. And again that seems to be about there. So I'm just going to very carefully and sometimes it helps to create a little bit more tension in the muscle to get a good cut by stretching out and opening out the cat. So I'm just going to make an incision and you can see the cut and it looks like I need to press a little bit hard. It's always better to err on the side of caution. And so then that creates a separation between one muscle group and another group. And so this is the upper boundary for this muscle. This is going to be the pectoralis major which is one of the muscles that we want to identify. And then I need to find the lower boundary for that muscle. And so for this I'm going to set the scalpel down. And for this it takes a little bit more close evaluation. So if you can see and I'll use the probe these muscle fibers there's a separation here. And this doesn't always happen but we're actually quite fortunate in this case. There's a clear separation and you can see that because of the connective tissue in between these two muscles. The separation between what is the pectoralis major and the pectoralis minor. So this is the major, this is the minor. And you can see this line here. And that represents the boundary between those two muscles. When we follow that all the way down we see that it connects or emerges at the sternum or the midline right around here. So that's where I'm going to make my cut for the lower boundary of the pectoralis major. Again just wanting to make smooth cuts. And so you can begin to see what is clearly an isolated muscle, the pectoralis major. So what I can do is go in and perhaps cut a little bit more deeply so as to better isolate this muscle. I might come back and do that and show how the muscle can be isolated both from muscles next to it and as well as underneath it. But I'm going to go ahead and move on and then isolate my pectoralis minor as well. So for the pectoralis minor this muscle, again looking to see where are the boundaries happening. Where can I see a change in the direction of the fibers? Or a line that will indicate a separation between the muscle. And actually for this cap it seems as though the pectoralis minor, the boundary of it is there. So this is the pectoralis major, this is the pectoralis minor. So I'm going to cut along that line. And sometimes it's good to outline using the probe first so that you can more clearly make the cut. So again just pressing down to create a nice taut surface for the cut. And then in just one smooth line perhaps following up for depth making that incision. We now have two muscles that we've been able to isolate. The pectoralis major and the pectoralis minor. And our division lines are here and here and here. So we have an upper border and a lower border for the pectoralis major. And then that same border that's the lower border for the pectoralis major is the upper border for the pectoralis minor. And then we have the lower boundary for the pectoralis minor. So these are the only two chest muscles that we are going to isolate. And you can do it for both sides, so for the cat's right side as well as the cat's left side. But instead of taking the time to isolate both of these superficial muscles, I'm going to designate one side as the superficial side and then the other side is going to be the deep side. Because there are some deeper chest muscles along the lateral side that we're going to need to isolate and they're going to require us having to cut into this area. So we aren't going to bother isolating these two muscles on the other side. So next, since we're already in the arms, then identify the biceps and the triceps. And the triceps are visible just on the surface, so this is one of the head groups of the triceps. The biceps, however, are underneath this muscle here. So this is going to require cutting across the midline of this muscle and reflecting the muscle back. So again, just for emphasis, the tricep is already revealed and the other head groups of that tricep are visible here. And so for the biceps, we are going to need to remove this top muscle. So in order to do that, we're going to create some incisions. And it's actually to get a better angle of this, I'm going to rotate the cat over to the dorsal side and make the incision where I see these two muscle groups. So I can see that there's this muscle group here and then the triceps kind of go underneath that. So what I want to do is just separate, go along this line and create an opening for that. So that's just enough of an opening so that now what I can do is take my probe and actually find where is this muscle on the underneath side. Alright, so I've been able to find kind of the access point in between the triceps and the muscle that lays over top that we're going to need to get around. So you can see how the probe has gone through to the other side. And that lets me know where the boundary is between this muscle here and the muscle that we're trying to bisect. So I'll kind of use that hole as my marker. And now, again cutting away from my body, just follow that line. And so now I've made an exit point. So now I can insert the probe here, reach over and it should come out over on the other side and indeed it will. So I'm actually just going to leave that probe inserted there to really help show where this muscle separation is. So you can see I've made the cut. And so now what I'm going to do, I'm going to again just leave the probe there because it's serving as an excellent marker. And I'm just going to make a cut to bisect this muscle. So I already know what the underneath part is because that's where my probe is running. And I can just make my cut all the way over to this side there. So I've been able to bisect that muscle and I'll clean it up just a little bit of the connective tissue. Alright, so we have bisected this muscle and if we reflect it back, then we can see now the biceps are revealed. So the biceps are a deep muscle. So you'll have to get to them by cutting the muscle that is superficial to them. Like I said, you can see the triceps here and so this is a sufficient reveal on this muscle. Alternatively, to see the entire group, this very, very thin superficial muscle can be removed. But I'm not going to because there's enough of a reveal on the tricep there. So we have the tricep, the triceps brachii, the biceps brachii and then we have here our pectoralis major, pectoralis minor. So those are the muscles in the chest and arms that we need. I'm now going to move down to the legs. And in the legs you can see that there's adipose tissue that needs to be removed as well as areolar tissue that needs to be removed. So you can see just how stretchy and spider webby that is. So again, using the technique of using the side of the forceps, I'm going to remove this connective tissue. So just get a better view of where these muscles are. And sometimes I'll close the forceps to kind of clear out a crevice without doing much damage. So that'll allow me to get in between this tissue or these muscles and really clear it out. And at some point you're going to run into blood vessels and you want to try to keep the blood vessels intact. However, if you need to cut one in order to clear out the tissue, that's fine. So again, using the hand can also be an efficient way of clearing out the tissue. But I now have a vessel that's attaching this tissue and so I'm just going to clip there and just kind of clean this up. And it looks like this muscle is pretty clean. Here's a really good shot of the areolar connective tissue. It's just super spider webby. That's what we want to have clear out. Again, another really good shot of areolar tissue. Now you don't want to go overboard and clean it up because the more connective tissue that's associated with the skin that I remove, the closer I get to the connective tissue, that's a part of maintaining the structure of the muscle. I really just want to get it to a point where I can see the pattern that these muscle fibers make. That's striped in appearance. So you can begin to see that in the leg. These really striped patterns. At this point I can begin to delineate and isolate these leg muscles. So they're again superficial muscles and deep muscles. So the superficial muscles up top we have the sartorias. So that's the anterior muscle here. And then the more posterior or in this perspective the more medial muscle is the gracilis. So they have sartorias and gracilis. And they are pretty well separated by these major blood vessels that run down the leg. So what I'm going to do is just make a very light cut right alongside of these vessels. And that's going to be the boundary between the sartorias and the gracilis. So now I can use my probe and just go along. And I can now isolate the sartorias and get underneath it and then see where it comes out on the other side. And there we are. So again we want to maintain the probe in this position because it's really going to help us know where we need to cut and where the separation is. You can see at the top of this muscle how it's already beginning to separate. So I just want to follow that separation. Again this is aerial artissue so it's really really easy. Again cutting away from me. And I don't want to go too far down because this is the insertion point. And if I go too far down I might just detach this muscle. So I want to leave it there. And then so now I have both boundaries of this muscle delineated and now I can isolate the sartorias. Now if I move over to the gracilis using the same cut that I made for the sartorias. The same strategy working the probe and seeing where this probe comes out. Let's see if we can't orient this with cap and the probe comes out there. So again I want to leave the probe in place to serve as a good indicator. And we're just going to follow the boundary that is created. Again this is loose connective tissue that's in between these muscles so it doesn't take very much at all to separate. So I'm going to clear out the connective tissue here just a little bit more. So I made a clear separation on either side and we now have the gracilis that's isolated. So because there are superficial and deep muscles I'm going to need to bisect these muscles to reveal the deep muscles underneath them. So I'm actually going to switch to the other side to do the deep muscles. I'm going to leave this side as my superficial side so that I can clearly see my sartorias and gracilis. Then I'm going to do the exact same thing that I did to the left side to the right side. What I want to do again just kind of work out to clear out that underneath connective tissue. I'm going to get the probe right at the kind of the midway point. Take my scissors. You could also do it with a scalpel. I just find it to be easier with the scissors and a little safer. And then just cut that muscle in half. Alright so then we reflect the muscle back and now I can reveal these deep muscles. And so underneath the sartorias are the muscles that make up the quadriceps. So there are four muscles and they are the vastus medialis, the rectus femoris, the vastus lateralis. And in between here is going to be the vastus intermedialis. And that's a much deeper muscle that we'll need to kind of separate the rectus femoris and rectus and vastus lateralis in order to see. So what I'm going to do now is just try to separate these three muscles. So this is connective tissue that again would need to be removed and I'll remove that later. But if you can see there is a muscle here, it's a very very thin muscle with that connective tissue. So the boundary of the muscle is there. Alright, that's not a muscle that we need. So we're going to ignore that and actually cut, this is a more dense connective tissue. And so for this it might be a little easier to use this scalpel just to cut through so that we can see the vastus lateralis as well as the rectus femoris. Alright, so I'm just going to reflect this back a bit more. And so now you can really see and actually closer to the origin of this muscle where this adipose tissue is, you can see the division between these three muscles. So this is the vastus lateralis, this is the rectus femoris, and this is the vastus medialis. So one, two, three, and then in between here these two muscles is the vastus intermedialis. And so the separation between the vastus lateralis and the rectus femoris is really tricky. So that's why I'm using the probe because it's really easy to tear the muscle. And so you really want to, and you might have to get, just look really closely to see where it is that the muscle actually separates. You don't want to create new muscles, you just kind of want to leave the muscles that are there in place. So it looks like I found the separation. And so we can see it, there's the separation. Between the vastus lateralis, rectus femoris, and then the vastus medialis here. Now what I'm going to do is just continue working to separate these two muscles so as to reveal the vastus intermedialis. So if you look, I've been able to separate the rectus femoris and the vastus lateralis to see a muscle deep down there that lies really close to the femur, and that's the vastus intermedialis. So it's a very, very deep bone or deep muscle that runs very, very close to the femur. So those are the quadriceps as we commonly call them. And then for the hamstrings, that's going to require a bisection of the gracilis. So again, want to use the probe as the marker, make the cut, reflect the muscle, and reveal. So the hamstrings are made of three primary muscles. The one here on the bottom, so you can see that there is this muscle here. So this muscle here, and then this muscle here. So the one that is a part of the hamstring is the bottom one. That's the semimembranosis. So this muscle here. Now for the other two muscles that are a part of the hamstring, one is going to be this really broad muscle, the biceps femoris, which runs along the side. And then if I turn the cat over to the dorsal side, the other is going to be the semitendinosis. And so to see the semitendinosis, I'm actually going to need to create a boundary between the biceps femoris and the semitendinosis. So I've kind of marked out where that division is with the probe. And so I'm just going to follow that and then confirm the separation. So I'm going to take this up just a little bit more. So we made that cut and that's going to be one of the boundary cuts for our semitendinosis, which is here. So the other boundary point is really in the medial portion of the leg. So dorsal and medial on the back of the leg. So here's the other. And so what I'm going to do is just use the probe again as a guide and follow this cut or the separation all the way to the top. So if the tail can get out of the way there, maybe I can lift it up. You can see this is the semitendinosis. So the three muscles that make up the hamstring, we have the biceps femoris here on the side, the semitendinosis here. And then you can kind of see the semitembrinosis from the dorsal view, but the ventral view is far better. And it is the bottom muscle here. So those three muscles make up the hamstring. The last muscle or the last few muscles that we'll look at are in the lower leg. And the first is the tibialis anterior, which you can see here. So I'm not going to do anything to really reveal this muscle. Perhaps it could be made along the tibia, but it's unnecessary. So the tibialis anterior here is one muscle. And then if we rotate the cat to the other side, this muscle, which we call our calf muscle, is the gastric demius. And that's just this muscle right here. So it's the calf muscle. And again, I could reveal the muscle, which I might take the time to do just so there's a clearer image. But I want to be careful in clearing out this connective tissue here, because if you notice, this connective tissue here actually serves as an attachment for another group of muscles. So you don't want to completely remove that. We just kind of want to create a window so that you can better see the gastric demius. All right, so I have the latissimus dorsi here on the superficial side. So I made the exact same cut that I made to isolate the latissimus dorsi. And I went ahead and bisected that muscle to reveal the deeper intercostal muscles. So these are the muscles along the rib that are really important in breathing. All right, and ordinarily there's a lot of fat. You can see this yellowing that's adipose tissue that needs to be cleared off. So I cleared off quite a bit of it already. So in order to see these muscles, you have to clear away the fat. And then if we move along the stomach, you have the rectus abdominal muscles, which they're straight muscles that run up pretty much the full length of the abdomen. And then continuing on you have the obliques. So you have the external oblique. Underneath that is the internal oblique. And then you'll have to look really closely to see the transverse abdominis, which, if you see there are these, the striped pattern there, which corresponds to the transverse abdominis. All right, so the transverse abdominis kind of extends over and so across the abdomen, whereas the internal oblique kind of stops short of that. So it's the external, the internal, and then more medial is the transverse abdominis. So with that, if we continue on to the back muscles, so in the neck you have the clavotropesius, the acromiotropesius, and the spinal tropesius here. And then, so those represent the tropesius muscles, and then the last muscle is the spinal deltoid. So clavotropesius, acromiotropesius along the shoulder blade, the spinal tropesius, which goes down to the spine, and then the spinal deltoid, which goes from the deltoid toward the spine. And the last group of muscles that we are going to look at are the erector spinae muscles. Now these are actually a group of several muscles that run along the dorsal side of the cat right along the spine, hence the name erector spinae. So these muscles are responsible for helping us to maintain posture. And so in order to see them, you actually need to remove a dense, irregular connective tissue. So it's already been removed here so that you can see the muscles. But in terms of how to get to this connective tissue, the loose connective tissue that you removed at the very beginning will help you get to this. And it'll look white, like it looks here. But when you get down to this level, you will not be able to just use your forceps to clear this off. It's just too dense. And so what you'll need to do is to create a little window, like I've already done, and you'll do that with your scalpel. And so you'll just create a window along just I guess maybe an inch and a half, inch square window to reveal those muscles. I'll do this again up here just so you can see when you first make the cut, there's actually a double layer of connective tissue. So that first cut will actually probably just get you through that first layer. And so again, just using the forceps and the scalpel I can create an opening here. And so this is the dense irregular connective tissue. So this is just the first layer. And so then there's another layer that will also need to be removed to actually get to those muscles. And again, the forceps will come in handy here to help you get through so as to reveal those muscles. All right, so these are the erector spine.