[Speaker 1] All right, so I know that this is kind of a weird introduction to today's lab, but for a few seconds I'm going to put up some stock footage of people, and I want you to appreciate, for just a minute, just how odd it is that we express our feelings by putting it on our face. That's not something very common in the animal kingdom. Here's a turtle. Here's a dolphin. What are these guys thinking? It's not necessarily that they don't have the ability to feel emotions— no one really knows what animals feel— but it's interesting that they can't display them on their face the way that humans can. That is a very uniquely human trait. As an interesting clinical correlation, this is something which is oftentimes taken away from people who have strokes, who have ischemic events. Oftentimes, you'll see patients who either temporarily or permanently lose movement of the muscles of half or all of the face, and a very common frustration they feel is that they lose their ability to non-verbally communicate. Oftentimes, they'll feel misunderstood, or will feel like they're losing out on part of a conversation, or will- feel something like that. And so my point is this, even though these aren't the big-muscle bodies with the big movers and all these really big exciting movements, the muscles of the face are still an incredibly important group of muscles. Not only are these muscles pretty uniquely structured in humans, but, once again, the way that we use them is pretty unique to us. Very few animals will communicate with facial expressions the way that humans do. And so, with that, welcome to Lab 9. Today we're going to talk about the muscles of the head, neck, and trunk. As I said with that introduction, I think the face muscles are probably some of the most important ones here, At least in terms of testability, but also- some of the most interesting ones so. As I said before, here are the four categories; here are the four ways that we're going to group them. We're also going to talk a little bit about the trunk today, and there's some pretty important concepts there that we'll go over, but... starting off with, uh, the muscles of the neck. The muscles of the neck- some of these should be familiar, specifically, the levator scapulae we talked about. Just as a quick review, we talked a little bit about the thyroid and the hyoid in- or at least we talked about the hyoid in Lab 3 and 4. So, uh, this is part of the axial skeleton. It's a floating bone. The thyroid is a gland just inferior to the larynx, and the larynx is your voice box. It's a cartilaginous organ. And so, we're going to use those as- as landmarks for some of the muscles here. Another important concept, if you look through some of these names, they're basically all going to be named by what structures they run between. The only real examples that break away from that are going to be the levator scapulae and the digastric muscles. Levator scapulae is going to be named for its action, and the digastric is going to be named because it has two bodies. So that word "di-" meaning two. and then "-gastric," meaning belly. So, this is going to be "muscle with two bellies." Cool, so here's a view of the posterior and anterior of the upper back and neck. Uh, there's a few muscles here that you might find familiar, specifically the trapezius and the deltoid. Let's remove those. Here we have some muscles that are deep to those. Specifically, we have our rhomboid minor and major— we'll talk about those in a second— but here we have the levator scapulae. Levator scapulae is, as the name suggests, going to elevate the scapula. On the anterior side, we have- oh, and we also have the posterior scalenes right there. I'll give you a better view of the scalenes in a second, just know that it means scale-like. It has many fingers, and we'll talk about those a little bit more in detail in a second. On the anterior side, we have the platysma. The platysma is the muscle that you can see if you- and you can feel on your neck if you pull the corners of your mouth as wide as possible. So, if you make, like, a disgusted face or if you try and show your teeth, this is the muscle that you can see when you do that. Going deeper to that, we have some of the main muscles in the neck here. Specifically, this is the sternocleidomastoid. Let's break down that word for a second. You might also see this as the SCM, by the way, but the sternocleidomastoid is going to connect to three structures: The sternum, obviously; that middle word, "cleido," refers to the clavicle, so it's going to connect to the clavicle; and then the mastoid- the mastoid process is on the skull, on the posterior side of the skull, if you'd remember from a few weeks ago. We have the sternohyoid here, is going to go between the sternum and the hyoid. Omohyoid; "omo" means shoulder, so this is going to connect to the scapula, so these- the shoulder to the hyoid. Omohyoid, again, you can see it- it appears to have two bodies. It doesn't technically have two bodies, but just be aware that it's going to go- you could see it- it- because it goes deep to some of the other muscles, it oftentimes appears to have two bodies to it, and that's why we label it twice. Sternothyroid is going to go between the sternum and the thyroid, obviously. And then let's, uh, let's see that from the lateral view. Let's see if we can get that from a bit of a closer, bit of a better view. So, starting off here again, we have the sternocleidomastoid, the SCM. Here, you can see it's connection to the mastoid process. This is going to be responsible for turning the head. In the back, we have the levator scapulae. And then, in this circled region, we have three muscles that I mentioned before briefly. These are your scalenes. You have a middle, an anterior, and a posterior. You can guess which one is going to be which. Uh, here we have omohyoid again. Omohyoid, once again, we'll label twice. Mylohyoid is going to be the muscle, uh, of the deep, um- how do I say that? Mylohyoid is going to be a muscle associated with the mouth. Um, the digastric here is going to be that muscle, once again, that has two muscle bellies to it. You can see, circled, the tendon that connects them. And then, uh, digastric once again. And then the last one is going to be the stylohyoid, which I think I mentioned before, um, when I talked about the hyoid being an attachment point for muscles. So, the styloid- the stylohyoid is going to go between the styloid process and the hyoid bone. I'll give you another view of that, just with a few of these guys labeled, once again, just to go even deeper, just to give you as many views as possible. Um, cool, cool. Now, I'll draw special attention to these guys again. These are the scalenes, scalenes, scalene means scale-like. You have a posterior, a medial, and an anterior. They help to stabilize the neck. Show you these guys one more time. These are from the study guide that is going to be posted on Canvas. [Chair thumping, noise] Alright now, moving on to the muscles of the face. These are all of the ones you need to know. The two major structures here that I want you to know in addition to these are going to be the trigeminal and the facial nerves. Those are both cranial nerves, so I'm giving you just a little bit of looking forward to it, um, a little bit of preview of it, because this is something that we're going to spend a lot of time talking about in the upcoming labs. As I mentioned before, these are muscles that are oftentimes damaged or- in which you lose a little bit of ability to use when you have something like a stroke or an ischemic event. And they are, as I mentioned before, even though they're not the big movers, they are still very important. Very few animals are going to communicate with facial muscles and non-verbally communicate the way that humans do. Now, you might think of some mammals, like cats and dogs, who can display a limited amount of emotions like aggression, but once again, the extent to which we use these is pretty unique to humans, or at the very least, the great apes. So, here we have some diagrams from the study guide. Let's go over some of these muscles right here. Starting off, we have the orbicularis oculi. "Orbicularis" means "circular," and then "oculi" means "around the eye." So, this is the circular muscle around the eye. Moving on, we have the levator labii. "Levator" means "elevate," so, based on the action, and then labii in this context is going to mean the lip. So this is going to be a muscle that elevates the lip. We have the zygomaticus minor and major here. Thankfully, uh, minor is going to be over major again, as is usually in anatomy, so... uh, zygomaticus is going to be associated with the zygomatic arches. Last one we have here is the risorius, or the laughing muscle. "Risorius," means "to laugh" in Latin, so this is going to help you laugh; it's going to help retract the cheeks. Next up, label number one here is going to be the occipitofrontalis. This is going to be be one of the muscles of your forehead. Um, It is going to go, as the name suggests, from the back region to the front region of the cranium. One of the few muscles associated basically only with the cranium. And there we go. Next up, we have the orbicularis oris- it looks like the "oris" is not printed there, but orbicularis oris is going to be the circular muscle around the mouth. Moving down, we have the buccinator. "Buccinator" means "cheek," so this is going to be the muscle of the cheek. And then depressor labii is going to do what the name suggests. It is going to depress the lips, pull the lips down. Now, I know I've mentioned strokes before, but I think it bears repeating. So, strokes are caused by blood clots in the brain— oftentimes multiple blood clots—occluding blood vessels, causing damage to downstream areas, areas profused by those blood vessels. And so, oftentimes, if the motor areas are impaired, people will have an inability to move many of the muscles of their face. They may also have difficulty forming words. These types of injuries are cerebral in nature, but the way that you detect them, the symptom, is muscular. The symptom is going to be, as I've said before, a diminished or an- a complete inability to move the facial muscles. Oftentimes, it is one sided. And this can be potentially lifelong, although it is surgically correctable on the bright side. In fact, that image you see on the bottom right is a before-and-after of a surgical correction. And so, people can have trouble forming words, people can have trouble chewing, or have trouble, um, looking around, or focusing their eyes on certain spots, but I think the symptom that's most relevant to our lab, and I think the symptom that, um, upsets a lot of people in a way that oftentimes they're not prepared for is the fact that you lose a lot of your non-verbal communication, and so that's why I bring it up as a disorder of the muscles of the face, as opposed to a, um, disorder of the brain- which, we might talk about it a little bit in that context next lab. But, once again, I just hope that clinical correlation helps. Moving on to the muscles of chewing. So, the two big ones that we've talked about before are the masseter and the temporalis. Uh, the masseter is going to put power at the canines, and then the temporalis is going to put muscle at the molars. So, those two are pretty famous. Those two are pretty large and visible, and we've talked about them before. The one that might throw people for a loop a little bit is the pterygoids. Uh, you have two pterygoids, medial and lateral. There's a few different heads of them, Um, they are going to be associated with the sphenoid bones, and they are going to insert on, uh, the mandible. These are going to be on the inside, so they're a little bit less visible, um, but these are going to be responsible for, like, a grinding motion of the molars. So, if you think about a cow or any animal that chews their cud, this is the motion that they're going to do. So, obviously, humans generally don't chew that way, So they're not going to be quite as prevalent, but these are still muscles that we have. Now, I've mentioned the cranial nerves before, I've mentioned these two before, but, um, I'll once again just mention them again very briefly. We'll talk about these more next week, but be aware that the facial nerves at- be aware that these two nerves are going to be responsible for innervating the muscles of the face. So, the facial nerve is going to descend from the stylomastoid foramen, and then the trigeminal nerve is going to descend from the foramen ovale. The facial nerve is going to be responsible for most of these- uh, most of the muscles of the face, and then the trigeminal nerve is going to be responsible for most of the muscles involved in chewing. And if you see those muscle- excuse me. If you see those nerves highlighted there, it kind of makes sense as to why each would be responsible for each. As another interesting clinical correlation, oftentimes you'll see people who do mixed martial arts or any sort of combat sport suffer injuries to facial nerves. Um, and so they'll oftentimes be able to move things not quite as well as they used to. Another interesting note is that, uh, these are nerves that can be damaged in something like diabetic neuropathy just because they are so fine, so that's why sometimes people who are late-stage diabetic will have, um, a decreased ability to move the facial muscles. So, facial nerve, and then the trigeminal nerve. This is the mandibular trunk. This is the trunk responsible for moving the muscles we just talked about, but there are other trunks to it too. All right, now let's move on to the muscles of the trunk. We'll start in the anterior, and then we'll move backwards. So, uh, at least a few of these should be familiar to you at this point. Most people have at least heard of the diaphragm. I know that we talked about the serratus anterior last lab, so, um- be aware that there are more muscles of the trunk than what we're going to go over for this lab, but these are the ones we expect you to study, and these the ones we hope that you can learn. So, starting off with the "abdominal muscles," um, there's essentially four of these. You have your rectus abdominus, which is, uh, what you traditionally think of as your six-pack muscles, your- These are the muscle bodies that you can see when you're at a very low body fat percentage. These are the ones that you, uh, work when you do something like a hanging leg raise, or a weighted crunch, or something like that. These are your rectus abdominus muscles. These are the classic ab muscles. You also have two oblique muscles, a, uh, external and an internal oblique. These are going to have a very similar function. They are both going to help lateral rotation of the trunk, so, this is what you might work by doing something like a Russian twist or a weighted, uh, trunk twist, something like that. Deep to both of these, you have the transverse abdominus, which is going to be the "muscle of the deep core." This is the muscle that's used in a vacuum pose, and I actually have an interesting clinical correlation for this too. So, an interesting note about the rectus abdominus. This is the muscle, once again, that you traditionally think of as being your "six-pack muscles." And something interesting about it is that it is going to have a different number of muscle bodies in different individuals, and that's just genetic. So, here we have Arnold Schwarzenegger, one of the greatest body builders of all time, and you can see from this pose that he only actually has four muscle bodies here. Compare that to Sylvester Stallone, who's on the left here, who is going to have much more. Once again, that's just completely genetic. There's nothing people can really do about that, but the two most important things to note about it is that it doesn't necessarily give you an advantage to have one versus the other. Neither has been shown to grant greater strength or stability or anything like that. And the other part of it, too, is that a lot of people kind of don't like that they don't have as many abdominal insertions as other people. But once again, Arnold Schwarzenegger, [laughs] at the lowest possible amount, so, you know, I- you're- worst case scenario, you're like him, you know? It's not necessarily a bad thing. The other kind of weird clinical correlation, once again, kind of talking about body building, is, uh- has to do with the transverse abdominus. And so, the transverse abdominus is actually really interesting. As we've said before, it's the muscle of the deep core, um, but it's also very weakly innervated. It's innervated by intercostal nerves, and then also some of the spinal nerves in the T7-L1 region. So, uh, what's interesting about it is because it's so weakly innervated, people who lose insulin sensitivity tend to lose tone in this muscle. So, the person I have on screen— his name is Dave Palumbo— and what you can see here, in addition to a degree of acromegaly, is that he has lost tone of his transverse abdominus, resulting in that bubble gut, or that bubble belly. This is colloquially known as palumboism, although that isn't a medical term. So, that's something you might encounter in people who abuse growth hormone, who abuse anabolic steroids, or who are pre-diabetic. And so, another muscle that's considered to be part of the anterior trunk, one that we've talked about before when we talked about the scapula, is the serratus anterior. I have the slide. It's from last week, um, when we talked about retraction and extension of the scapula, but, uh, once again, the serratus anterior, just as a quick review, is the punching muscle. This is a muscle, uh, that's very prevalent on people who do boxing or other types of striking. Um, very prevalent on construction workers too. But, it is going to, uh, insert on the ribs, and it's going to help draw the scapula forward, so. Serratus anterior, right there, and then we have our rhomboids and serratus posterior, but serratus anterior is the key focus of this. Next up- and this is a- a subject I cannot emphasize enough, there are quite a few test questions about this, and so I highly, highly recommend knowing it as well as possible. These are your breathing muscles. The two that we will talk about here are your diaphragm and your intercostals. The diaphragm, just to be clear, during contraction, moves downwards, so you can see the diaphragm in this picture is going to be in a relaxed position. When you breathe in, the diaphragm is going to move towards the inferior aspect of the body, and that is going to allow for inhalation. The idea here is that it's going to increase the volume of the thoracic cavity, allowing the lungs to fill with air. Then, during relaxation, just the opposite is going to happen. The other muscle that can assist in that is your intercostal muscles. As the name suggests, the intercostal muscles are going to be between the ribs. Contra- during contraction, they are going to, uh, excuse me- During inhalation, they are going contract. During exhalation, they are going to relax. Once again, that's a very highly testable concept, so please make sure that you have that straight. And now we move on to the last section of muscles that we have to talk about today. That is the posterior muscles of the trunk. Some of these should actually be familiar as well. We've already talked about the rhomboid minor and major. That was a few slides ago. That is going to help to add, duct, or pull back the- the scapula. I would describe that as retraction too, I don't know why the book doesn't, but the rhomboids I would consider to retract the scapula. So, we've talked about those before. Then we have the spinal erector muscles. We have the muscles of the back of the trunk here. Let's go through them. So, here we have another superficial to deep. From the superficial-most, we can start with the trapezius, the latissimus dorsi, and the deltoid. I hope that those are familiar f- to you at this point. I've mentioned them at least a few times. Let's peel those away. We have the serratus posterior inferior. We have the rhomboid minor- or, I'm sorry, we have the rhomboid major, the rhomboid minor. We have the levator scapulae. Also not shown, deep to the rhomboids, is the serratus posterior superior. So, let's take all of those away. Now we have three spinal erector muscles, the three deepest muscles of the spine. So, the three major spinal erector muscles are: The spinalis, this one is associated or closest to the spine; You have your longissimus thoracis, which is the longest muscle of the thorax, hence the name; then you have your iliocostalis. This is going to go from the iliac region to the ribs, so Iliac to costal. Um, it's worth mentioning again, there are other muscles here that we don't expect you to know. There's a lot more muscles to the back, but moving on. Next up, we have the splenius muscles. Now, the textbook, the- that lab manual, that is, doesn't actually make a distinction between the two, but they are considered two separate muscles. You have your splenius capitus and your splenius cervicus. Uh, they are going to work together. They accomplish very much the same thing, but they are considered two muscle bodies. Essentially what these guys are going to do is they're going to help you turn your head to the side. So, the motion you can think of is, imagine putting your head on your shoulder. Once again, the spinal erectors. I'll draw special attention to these- these facilitate upright posture, and so they're very important in humans with our strange bipedal form of locomotion. Once again the insertions are gonna be-or, I'm sorry. Once again, the origins are going to be on the spine, the insertions are going to be on the rib, and these are oftentimes considered the muscles of the lower back. uh, this is a bit of a misnomer because these are obviously going to go almost all the way up the thoracic cavity and through the- the rib cage, but the only time that you're really going to be able to see these on a person, on a well conditioned athlete, is in the lower back. So, oftentimes, these are considered lower back muscles. The way that oftentimes you'll work these out, or you can activate them, is with a back extension, which is what that demonstrator in that picture is doing. So, hopefully, that helps keep things clear. And then, that brings us to the end of today's lab. Uh, the review content is Labs 15 and 16 in the lab manual. And then, I just want to draw special attention again to those four high-yield concepts. That being the facial muscles, they are very highly testable. Breathing is another concept that I think a lot of people overlook. And then, just reviewing the skeletal system, things like the hyoid, the mandible, the thyroid, um, things like that, just so that you can get the muscles of the neck down correctly. And with that, thank you for your attention today, and good luck on this week's lab.