- [Lecturer] The topic of this video is the skeletal system and specifically the skull of the skeletal system. All right. So we're going to start with a couple of different views. We're going to be looking at the outside of the skull, and let's first start by drawing out two different views of our skull. So, just draw along with me. And these never have to be perfect. Mine are never going to be perfect. I'm just gonna try to make them as good as I can. All right. So that is the frontal view of the skull. And essentially, this is where we talk about views in terms of where we're standing when we're looking at someone. So we're also going to draw a lateral view of the skull down below. Alrighty. So let's just add in an eye socket here and we're almost done. Alrighty. So now we've got the outline for our skull. Sorry, I left that out of the picture a little bit. Okay. We're going to identify a series of different bones and they are, for most of them you'll be able to see them on both views of this skull, but some you may only be able to see in this lateral view. And so I'm always gonna, whenever I remember label, right and left, doesn't really matter here because it's the same on both sides. But just so you know what view this is gonna be anterior and posterior. All right. So let's start with our nasal bone. You guessed it. It's right around where the nose is. It's gonna be right there and I'm just gonna color it in. It would help if my markers were better but I'll get rid of this marker in a second. And we can see the nasal bone from the frontal view. And also from the lateral view right here. Now, I'm just gonna write it off to the side. Remember our color is always going to be associated with a different part of anatomy and I'll write the name that that color is associated with to the side. So that's gonna be our nasal bone. Okay. Now, let's draw our frontal bone. And so, all of these are different parts of the skull. So this big piece where the forehead is basically is our frontal bone and it's easiest to see on this frontal view. So, again, as always, I encourage you to color along with me it's really just gonna help so much visually. That's how I learned anatomy the best and it has worked great for students in the past. And I'm trying my best to make things as proportionate as possible. So I know you'll do the same, but that's why I also encourage you to keep a textbook around to really make sure that you're getting the idea even if things aren't exactly proportional. So again, that's our frontal bone. Now, let's draw in our maxilla. The maxilla is gonna be all of this, basically around the nose area and on the upper part of the mouth. And again, just like most of these, you'll be able to see it in both this frontal view and the lateral view. That is our maxilla. Now, people will often get the maxilla mixed up with this next bone. So just make sure that you're paying attention to differentiating between these. The next bone is our mandible. I think it's because they both start with an M, I think that's why people usually get them confused, but your mandible is like your jaw bone. That's how I kind of remember. I also know that the maxilla is above the lip. So for some reason I kind of picture ever since I learned anatomy years and years ago, I kind of pictured a guy named Max with a mustache. And that's how I remember that it's maxilla up near where the mustache is. But use whatever method that works for you as long as you know it. One for this class. And then later, since a lot of you will end up in clinical situations you wanna make sure you know your bones if you end up dealing with a real patient. So those are mandibles. Now, let's draw in a bone called our zygomatic bone. It's kind of a fun word to say. Again, just like all of us, we're gonna have it on both sides. So it's always gonna be symmetrical here for the most part. You know, they're always anatomical differences or sometimes people don't have quite as much exact symmetry, but for the most part it's gonna be almost exactly the same. Another zygomatic bone here is gonna be seen right there in the lateral view. And we're unintentionally creating a nice little rainbow skull for ourselves. All right. Next let's do our temporal bone, which is right where we, the area that we call our temples. That's right where our temporal bone is. See anatomy isn't that hard. It makes sense, right? So that dark green is our temporal bone and we can also see it down here. Perfect. So that wraps up our temporal bone. Now, just one left that we'll be able to see on both. And that is our sphenoid bone. Now, the sphenoid bone is kind of odd and you can actually see it a little bit more inside of the skull. So we'll also take a look at that inside view. You can see it a little bit on the outside as well. So I'm gonna draw it in right here in pink. I wish those colors were a little bit different. I'm gonna draw a little line because I unintentionally, just with a pencil, I unintentionally used colors that are kind of similar right there. So I wanna just make sure that you can see that line in this video. So there's a clean break between zygomatic and sphenoid. And then same thing here. Just draw a little line in, sorry about that. I didn't realize they were gonna be that similar. Our sphenoid bone is gonna be right here. Sphenoid is also a funny word and then kind of coming through right there. So that's sphenoid. Now, we have two more skull bones that we're only going to be able to see in a lateral view. So our first is our parietal bone which is gonna be this whole big area right here. That is our parietal. And the last bone we have is the occipital right down here. Now, as you're learning the names of these bones keep in mind that we're also going to be learning the different lobes of the brain and they're associated with different names of the bones here. So the better you know this, the better our neurology section is going to be. So just a quick recap. This is our frontal view. This is our lateral view and we just went over our nasal, frontal, maxilla. Remember that's like right above the lip. Mandible which is the jaw. Zygomatic, which is on the side there. Temporal, which is usually where people say their temples are, where they have a headache. That bone is actually really thin. And I used to work for another faculty member at Coastline Dr. Henry, and she used to be a neurosurgeon. And she has talked about how thin the temporal bone is before and talking about like emergency surgery where she actually has to just break through that bone super quickly to be able to get to the brain. So make note of how thin that is when you're looking at the models. We have our sphenoid bone, which remember we can't really see much of on the outside here. We can see a little more on the inside when we take a closer look at it later, and then we have our parietal and occipital bone. So this covers overall the outside of the skull. Now let's take a closer look at part of the inside. Alrighty. Now, we're going to look at the inside of the skull. So I'm just gonna say skull inside. So here, this is gonna be a superior view which is looking from the top down into the inside of the skull. So let me draw this out. I'm gonna do my very best to make it as good as I can for you. And you'll be able to kind of compare this to what's in your textbook and what is in models. So your skull's kind of oval shaped. And I'm going to first draw in a couple of different parts of the skull in addition to a few different things that we call foramen, which are holes. So just hang in there with me as I draw some things out. Okay? And draw along with me, please. So remember, like we said everything is going to be symmetrical. So if there's a hole on one side, there's gonna be a hole on the other side. So all of these holes are currently meaningless but let's add some meaning in. First of all, I'm just going to write an A here for anterior and a P here for posterior. So let's get started. A few things that I want to, oops, I forgot one little part. Hang in there with me. I'm sorry. I know this is taking a little bit of time. Okay. So let's first label some parts of the skull itself. And then I'm gonna talk about all these little dots everywhere, which are called foramen which are basically holes. For most of those holes, you're actually gonna have cranial nerves moving or traveling through them. So cranial nerves are nerves that have to do with your brain and we'll get into the function of those as we get into our neurology section. So just kind of stay tuned for that. But in terms of these foramen, we will review the cranial nerves and sometimes other structures that pass through them. But first let's talk about the different sections here in the skull. So we will start out with three different fossas. Let's see, how do I want to do this? All right. We're gonna do some markers here basically from here, all of this, I'm just gonna do this on one side of the skull even though remember everything is bilateral so equal on both sides. But where this turquoise little marker is that is our anterior fossa. 'Cause remember, we're a superior view looking down on the inside of the skull. And this is the front. This is the back. So this is anterior and this is posterior. So this right here is our anterior fossa. All right. Next we have our middle fossa right here. Remember, there's one on both sides. And then if this is the anterior fossa right here what do you think this is gonna be? If you guessed posterior fossa, you're right. It's also sometimes called the occipital fossa because that is where our occipital bone is. And we just learned that when you're looking at the outside of the skull. So that is our posterior or occipital fossa. Let's see. We're gonna label a few more things. You have a little piece of bone right here that sticks up right in the middle there. That is going to be called crista galli. And that actually means the crest of the rooster in Latin, which, you know, anatomy is basically all Latin. So anyway, just in case, basically that sticks up in the air and it comes out towards us. So it comes up superiorly. So it kind of looks like the top of a rooster if you picture that in your brain. Yeah. So let's see, I think. One more thing that I want us to draw out, and that is our petrous ridge, which is this structure here. I'm just gonna color it in for us. And you will be able to see that on the skull in the model, but it's just this little ridge. I think that's it. All right. So those are the main structures that I want you to know in terms of this view of the skull. Now, what I want you to do is we're gonna switch gears and go into the different foramen or the different holes in the skull. Alrighty. So our first one is going to be our cribriform plate, which is actually part of the ethmoid bone. But our cribriform plate is right here. And basically that structure, the crista galli sticks out from it. So again, I chose two colors that are pretty similar. So I'm just gonna draw a little outline here so you can see distinctly where the border of the cribriform plate is and where the crista galli sticks out. Now I'm gonna add in a couple of little black dots here to remember this and let me explain that in just a second. So first let's label that it is our cribriform plate. Now, I drew those little black dots because remember we're talking about foramen here meaning holes that nerves travel through. And remember I mentioned that most of the things that travels through these holes are cranial nerves. Now what I'm gonna do for all of these things that we're going to label is I'm gonna put in parentheses to the side the Roman numeral of the cranial nerve that passes through that foramen or that structure. So for the cribriform plate, cranial nerve I will pass through the cribriform plate, actually, through where those black holes are. So just make note of that. And I'll do that for every other different frame that we have. So I'll just put a little bullet there to organize ourselves. Now, what's interesting about this cranial nerve is most of these cranial nerves will travel through as one big, almost like a cylindrical type structure, like an actual nerve. This is broken up into teeny-tiny little nerves passing through these little holes that are represented by the black dots. And what's interesting is that's cranial nerve number one passing through that which is your olfactory nerve. You don't need to know this right now but this is just like a side note that we'll learn later. But it's interesting because that is actually your nerve that controls smell. So during car accidents with like a really strong jolts, oftentimes, you have these little teeny-tiny nerves coming through all of these holes. Oftentimes that nerve will get damaged. And so something that's pretty common after a car accident or a sudden like traumatic event like that is loss of smell because those nerves are so vulnerable and tiny traveling through that small space compared to these really big holes down here with nice thick nerves traveling through. So that's just a fun fact nothing that you need to know right now other than what we're writing down. Alrighty. So now let's talk about, let's see let's go down our list from like here down. So our next one is going to be our superior orbital fissure. Right here. And fissure is kind of another name for a foramen but a fissure is just longer and more narrow and like a little bit jagged is basically what a fissure means. Now, through this superior orbital fissure you actually have a bunch of different parts of cranial nerves traveling through it. You have cranial nerve III. And just for future reference, we always identify cranial nerves with Roman numerals instead of written numbers. So, cranial nerve III, cranial nerve IV, and the first branch of cranial nerve V, as well as cranial nerve VI all traveling through that, which makes sense 'cause it's pretty wide and flat. So you have a bunch of stuff traveling through. Now, next to that you also have your optic canal which is right here, those two little blue dots. And what makes sense is the name of the nerve often coincides with the foramen or the whole. So this is technically your optic canal which is still foramen. And what travels through there is your cranial nerve II, which is your optic nerve. So once we learn the names of these nerves we'll really hope you remember which ones will pass through each foramen. All right, now we have foramen lacerum. Now for foramen lacerum we'll color it in but I don't need you to know what travels through it. There's kind of some smaller structures. So just don't worry about that right now. But it's right here. Foramen lacerum. And it's actually named lacerum because it looks like a laceration because the sides are a little bit jagged. But again, we don't need to know the structures that pass through there, 'cause they're a little bit smaller and not as significant for us. Oops. And you know what? I just realized there's something right next to it that I forgot to label. So let me jump in here super fast and I'm gonna label one extra thing. I'm gonna use a dark green color and just color this in. This structure is not a foramen, but it's something that we call our sella turcica. So I'm going to write it up here 'cause it's not a foramen. Sella turcica which means Turkish saddle, which is, it actually kind of looks like a little saddle hill here. So it's easier to see in like 3D forum. But if you can see it it really is kind of like saddle-shaped. So I forgot about that. But anyway, jumping back over to foramen, the next one I want to show you is your foramen rotundum. That is this little one right up here in brown. Foramen rotundum. And the cranial nerve that passes through there is the second branch of cranial nerve V. So we're gonna write V and number two. Remember number one was up here through a superior orbital fissure. The next one is foramen ovale. Foramen ovale is the larger foramen right here in the middle fossa. And that is going to have the third branch of cranial nerve V. And then the last one in that middle fossa is our foramen spinosum, which are the little pink dots that I just colored in. Foramen spinosum. Actually, we don't have a cranial nerve that passes through there. We actually have the middle meningeal artery. Oops. I spelled that wrong. It should be M-E-N-I, meningeal artery. And whenever I write artery I'm gonna abbreviate it with aa. Same thing with vein, vein will be vv, and muscle will be mm. So I think I already told you about the muscle one and I'll remind you about the other ones next time we use them. All right. So one thing that people often get confused on is these foramen right here. So I came up with a little acronym type thing. It's not very complicated, but basically I'm separating these three structures that are kind of on their own in the middle fossa and giving them the abbreviation R-O-S for rotundum, ovale, spinosum. 'Cause people often kind of try to throw in foramen lacerum and they kind of get these two confused when we're looking over them in lab. But for these structures that are just on their own, on the outside in the middle fossa, remember anteriorly to posteriorly, we're gonna say R-O-S, rotundum, ovale, spinosum. And lacerum is just kind of like on its own over here. All right. So let's keep going. We're gonna move down to the foramen that is in the petrous ridge. So that is, let me find a color for that. That is our internal auditory meatus. It's gonna be this light green color. Internal auditory meatus. And for that, it's gonna have two different things traveling through it. It will have cranial nerve VII and cranial nerve VIII. All right. We're almost done here. Hang in there with me. Our next one is going to be the jugular foramen. Those are the ones right here. I'll make them light blue. And there's quite a bit in here that travels through there. So, we're going to have our internal jugular vein as well as our cranial nerve IX, X, and XI. So, IX, X, and XI. I always have weird ways of remembering things and my way for remembering this is that you know how like in movies and in scary stuff they're always talking about like, they went right for the jugular to try to kill something. If that's like a lion trying to kill it prey or whatever. So I think about that because the jugular has to be super important, right? Because it's a main vein there and it's where predators will always attack. So I'm like, "You know what? This is something important. It has a bunch of things going through it. So it has to have a vein named after it." And then IX, X, XI for some reason this is a little bit of a stretch. But when a lion killed its prey, when something is dead, they oftentimes put Xs over it. So I remember that as the number 10. And then I remember, oops, we're gonna have one before that and one after it. I know that sounds kind of crazy, but you know what? Sometimes you need crazy things to remember different parts of anatomy. And if that's how your brain works, all for it. If it doesn't, no worries, it's all good. I'm just throwing it out there in case it could possibly help you. Two more to go. Let's do our hypoglossal foramen first. I'm gonna make those dark blue up here. And once we learned the names of the cranial nerves this will be even easier 'cause the cranial nerve that travels through it is our hypoglossal nerve. So that is our cranial nerve number XII. And last but not least, we have a huge foramen, our foramen magnum right here. And that's actually where our spinal cord travels through. But we're just gonna give it a name 'cause there's no cranial nerve passing through it. That is our foramen magnum where our spinal cord and brainstem end up passing through. So, now we finally have the inside view of the skull. We have all these structures to identify on it and then we have all of these different foramen going through it with a bunch of different cranial nerves and a few other vascular structures. Now for the skull, we have a few more internal bones to cover. These are bones, some of which we saw in the other figures but I just wanna give you a different view to be able to see them a little bit easier. So I'm gonna draw a little skull right here. This is just gonna be an anterior view of a skull that's super simplified here and then we're gonna have these eye sockets like we did in some of the other ones. And then I'm also, so this is gonna be interior view and this is the right and left. Then I'm also gonna give you a lateral view. So this is a lateral view of a skull. This is anterior and oops, I wrote an R, I should've written a P for posterior. That's my mistake. So, we have to label some stuff. So we've got our ethmoid bone. Remember our ethmoid bone is where our cribriform plate is, so I just wanna show you this is gonna be an internal view. So it's as if we're looking through the first layer a little bit deeper into the skull and looking at the internal bones. So, we have the ethmoid bone right here. And then a little bit more medially, we have the lacrimal or tier, that's what it means. So it's like right where those like the medial portion of your eyes are. That's where your lacrimal bone is. Now for this lateral view, there's a bunch more things we can see. So we have the sphenoid bone, so remember, we're looking at the internal part of this skull, so at the inside. So you're gonna have the sphenoid bone. It's gonna look sorta like this on the inside. This is very simplified. But when you look up a picture of the sphenoid bone and the model or in the book it's gonna look pretty complex and you'll see how this is simplified. So that's our sphenoid bone. And then that's what is on top of that is our sella turcica. Remember we drew that in the other view of the skull as well which means Turkish saddle. And then actually what I wanna point out is you have something that sits in the sella turcica and that is actually your pituitary gland. So that sits right there. And that's gonna be important for us to note the location of the pituitary gland and actually our optic nerves. Remember, if you look back on your skull drawing before I'm gonna pull it back in. Here is our sella turcica and this dark green here. And we have our optic nerves that come in through right here through the optic canal. And what happened is your nerves pass through where this, sella turcica is, this Turkish saddle. But your pituitary gland is sitting right there. And the way that the optic nerves are oriented what happens is, if you get a pituitary tumor in this gland that's sitting right there oftentimes people will lose their peripheral vision. So if anyone is losing their peripheral vision oftentimes what they'll do is they'll do imaging of the brain to see if there is a tumor of that pituitary gland that could be contributing to that loss of peripheral vision. So anatomy is super cool and important in that way. Now let's review a few other structures. So we have our, let's see. We have our external auditory meatus. Remember we had an internal auditory meatus before but now this is the external one. Auditory meatus. This is something that we'll see more externally. So this sphenoid, sella turcica, and pituitary gland those are all like deep inside. And then the external auditory meatus is external. And a few other structures you'll be able to see externally on this lateral view is also something called your mastoid process, which is right about here in this blue color. And process really just means anything that's sticking out. So it's like this little chunk of bone that's sticking out on the skull. You're also going to have a styloid process which is gonna come down right about here. And then I remember that because styloid process kind of reminds me of stiletto. And that kind of looks like the heel of a stiletto shoe. Now you have your mastoid process, and your styloid process. Now in between them, you're gonna have something called your stylomastoid foramen right here. And it takes a piece of both of those words. And what's actually going to travel through that foramen is cranial nerve VII. So that's one that we can only see on the outside. And that's why I'm including it here instead of in that other picture where we drew the, it was like the inside view of the skull with all those other foramens. So this is the only one that we left out. Now, one other little thing to add here is something called your inion or your external occipital protuberance. That's like a little part of the skull that's sticking out right in the back there. All right. So we covered some internal bones, the ethmoid, lacrimal, the sphenoid that has a sella turcica with the pituitary gland sitting on it. And then we also covered some things that we can see externally in this lateral view like the external auditory meatus. These two processes, the foramen and then the inion. Now, let's continue taking a look at internal bones but I'm gonna just draw a little line here just to separate things so we can keep it clear in our brains. And you know how we have like these little eye sockets. Well, I'm gonna give you an anterior view of these. They're eye sockets, but they're actually called orbits. So I'm gonna give you a little view of them, a little closer together than they usually are. So this is gonna be an anterior view of orbits or eye sockets. Now within them, you're gonna have a few different things. You're going to have different canals that you'll be able to see. So I'm just gonna draw them out. The first one is the optic foramen which is also sometimes called the optic canal that we pointed out in that first picture. So I'm gonna bring that back in in a second after we review the other two. So in addition we're also gonna have the superior orbital fissure which you will be able to see inside of the orbits or the eye sockets. And lastly, the inferior orbital fissure. So just pointing a few structures out in our last picture. Here's our optic canal. And then we have superior orbital fissure right here. Those are things that we can see from the inside superior view of this skull. So essentially, it is like a transverse cut through someone. And that's how we're looking down inside the skull. And then we can also see those things, here is our optic foramen and canal. Remember, this is us looking at the front of the skull and interior view. We can see through these eye sockets, we can see the optic foramen or canals, that superior orbital fissure, and we can also see the inferior orbital fissure as well. Now, let's finish up with just a few more bones. I'm going to show you the, so we looked at the inside of the eye sockets or the nose right there, or excuse me, the eyes. Now, I'm gonna show you the inside of the nose. So you know how we have that opening right about here. And then we also have the opening in our original drawing, here, right there and right here. So I'm gonna show you what it looks like inside the nose right there if we're looking through it. So inside our nose. Let me draw a little finger. This is what it looks like. And we're going to have one structure in the middle which is going to be called our vomer or inferior septum. You may have heard someone saying like, "I have a deviated septum." And that makes it harder for them to breathe. So that's what they're talking about here. And we're also gonna have something called turbinates or conchas. So I'm gonna draw those out for us as well. They're gonna look like this. You can't actually see the superior turbinate when you're looking at the model. So just keep taking note of that, but we're just gonna draw three because there are three. So these are the turbinates or also called concha. And something to note is that the turbinates, I'm just gonna write down what they mean. Their turbin means to warm. So these structures assist in warming contents of the nose. And there is a superior, middle, and inferior turbinate. So that's superior, middle, and inferior. So that's inside of the nose. And I promised you before that we would take a closer look at this sphenoid bone. So let's do that. All right. So for our sphenoid bone, it means wedge-like. That's just what sphenoid means. Now I'm gonna draw it pretty simplified but you can take a closer look at it when you look at the figures and when you look at your book. So we're going to be looking at anterior view and I'm gonna draw this. Again, this is very simplified. Alrighty. So here is our right, and here is our left. You have greater wings that are kind of just like this. It's a better part of this area right here. Those are greater wings. We also have a lesser wing, but it's just not pictured here. So I'm just gonna have you learn just this, the greater wing. And then, we're going to have something that we'll call lateral pterygoid processes. So we're going to have a right and a left. And remember, medial is more towards midline. Lateral is away from midline. So that's why these are lateral and these are medial. Right and left lateral pterygoid process. And then since we have that lateral what else do you think we're gonna have here? That's right, you guessed it. It starts more medially here. So it's going to be our right. Oops, our right and left medial pterygoid process. So that's all I want you to know for now. Again, there is like a lesser wing up here and some other parts but these are the main pieces I want you to know of the sphenoid. Now, one final thing I want to point out is the bottom of the skull, which is the inferior view. I just wanna point out one main structure that we can only see from the bottom. So I'm gonna attempt to draw the skull out here. So we're looking at the whole skull but the bottom side of it. So this right here is gonna be our mandible and then we're gonna have foramen magnum, and then we're gonna have two different things right there. So just for reference, this isn't the first time we looked at foramen magnum but I just want to point it out as a point of reference. I also want to point out that this is interior and this is posterior because we're all looking at the bottom view of that skull. So, foramen magnum and there's gonna be two little pieces on the skull and the front there that I wanted to point out for you. And those are going to be your occipital condyles. So those are important because that's where your skull will, we call it articulate, but really that's where your skull will form a joint with the highest bone in your spine. So that's how your skull connects to your spine. So that's why that's important there. And that's the last piece that we are going to learn in terms of the skeletal system and our skull.