Welcome to our next chapter of study nine which is articulations now of course we want to make sure that after we've done all our studying of this particular subject we can look up and say okay how do I know I got it how do I know I understand it so here are the learning objectives that you can use as checkpoints along the way now if we go dive right in and we Define an articulation we you know a lot of people refer to these as as joints and really what we're referring to is the site where two or more B bones interconnect now it can be more than just bones interconnecting we can also use articulations when referring to where we have a substantial amount of cartilage interconnecting with bone as well as where a tooth is going to interconnect with bone now as we dig deeper into this we're going to see we have two classifications for articulations we have the functional classifications which is going to refer to how much movement is allowed or restricted at the joint or we can look at them structurally so we can classify them based purely upon the parts the shape of those parts and how they interconnect with the other part meaning the bone or the cartilage or the tooth that makes up the articulation first we're going to look at functional classification now functional classification is very straightforward um this one you know you're kind of like yeah yeah three I can handle classifications and these are honestly again pretty easy to understand so when we look at these we see first we have a synarthrosis the plural would be synarthroses and what this is referring to um this is referring to an immovable joint so I like to think of this as meaning it would be a sin to move at these joints perfect example of this is going to be the cranial sutures so when we look at our coronal sagittal squamous and lamboid sutures we are looking at dense fibrous connective tissue between those interconnecting bones and therefore we do not permit movement because really what we're doing is we allowed for the expansion of the brain within the skull and then we solidify that skull for means of protection now maybe it could be nice to be able to lift one of those bones and look under the hood if we needed to but I kind of like the protective feature more now our next type of classification is an amphiarthrosis so you kind of think of this as like does it move and you can say if if you know kind yeah a little bit and so these are slightly movable joints example for this would be the pubic symphysis recall that this is where the coxal bones are coming together anteriorly with a wedge of cartilage in between so every time you step down you kind of radiate that mechanical stress up you know proximately through that lower limb and so this way we can kind of have that little shift of the coxal bones against each other so that we're not you know grinding the bone against the bone they can shift against each other allowing a little bit of movement to relieve ourselves of that um weight distribution and that stress with the steps we take now we have lastly a diarthrosis or diarthroses and this friends is pretty much like when you initially think of articulations and Joints this is what you're thinking of a diarthrosis is a freely move movable joint and this is what you have the most of in the body so when you think of things like your shoulders your hips your elbows your knees you're thinking of diarthrotic joints now oftentimes when we think of the anatomical terminology when we refer to a joint we usually refer to the parts of the bones that are articulating with one another so when we say shoulder we're actually referring to the glenohumeral Joint so we have the glenoid cavity of the scapula articulating with the head of the humoris our shoulder when we get to the structural classification this is when we get a little bit more into the weeds in our study um so to ensure that you you know don't get totally lost in the sauce as you dig into these um I want to make sure that you understand that you have a syn opsis of all of this in table 9-1 this is a chart that pretty much cross references the structural and functional classifications of joints so again this would be probably something nice to have out during your studies just so you can always kind of have that frame of reference I'm going to go ahead and initially talk about the basic structural classifications of joints and then you'll notice in the coming slides that I'll kind of cross reference it with the functional classifications as we get a little bit more detailed so when we look at purely looking at the structures that make up joints we have fibrous which is going to be dense connective tissue with lots and lots of fibers in it uniting those bones so we already kind of mentioned an example with this the cranial sutures but that's not the only type of fibers joint we have we also have bony joints this is where we're going to have either fibers or cartilagenous joints meaning where we had two bones that were either had dense connective tissue or cartilage between them and pretty much what we're saying is we have two bones and they essentially aify between the two fusing them together as a larger bone um and this would be like the metopic suture that we had in our bone list um to study for chapters uh for chapter 7even now when we look at the cartilaginous joints pretty easy cartilage is in the name so we have bones that are interconnected by cartilage now that cartilage can be comprised of something that resembles Highland cartilage or it can consist of fioc cartilage and then we have sovial joints and friends this is where you can have a little sigh of relief because all sovial joints are also functionally classified as diarthrotic joints that's a that's a one to one right there now the nature of synovial joints is that we encase the ends of the bones in a capsule that is going to support the the freely movable nature of that joint so if we dive a little deeper we go to looking more at fibrous joints We have basically three types that we can see the one we've mentioned a couple of times already is a su so remember this would be a dense piece of dense fibrous connective tissue between two bones now this would be a synarthrotic joint because remember it's a syn move between those skull bones then we have a syndesmosis syndesmosis is indicating that these bones are going to be connected again by a sturdy piece of connective tissue but in this instance it's going to be not so much a membrane like the sutures we saw it's going to be a ligament so there's going to be a little bit of movement loud because of this band of tissue connecting them and so we refer to these often as amphiarthrotic joints and so this would be like if you looked at the distal portion of the tibia and fibula where they are you know pretty much positioned parallel we have a strap if you will of ligament between the two so it allows them to have a little bit of movement parallel to one another especially like you know when you're stepping down or kind of have that rolling nature of the ankle occur when you step down like on a curb and so that ligament is going to keep them intact with one another but also allow for a little bit of movement between the two and then we have a gomphosis now a gomphosis is going to indicate the articulation between a tooth and its bony socket so this is referring to the teeth as they articulate within the Mand and the maxilla now there is a piece of connective tissue that is ensuring that the tooth is stabilized within that socket and that's referred to as the perodontal ligament and so we refer to this as a synarthrotic joint now you can kinding to think of this one pretty easily because your teeth fit in your gums right so gomphosis you can think gomphosis gums oh yeah that's where the teeth fit into the to the bones and remember this should be a synarthrotic joint because once you have all your adult teeth it usually is a bad thing if you can wiggle an adult tooth in your mouth we don't want that now we have the Bony classification for joints and really we only thing we really have to represent this is a sinosis and like this is where we have excuse me this is where we have two bones that were either either had either they were the fibrous meaning they had that dense connective tissue between them or they had um a wedge of cartilage between them but they have since grown into one another so again that would be like the metopic suture that we see um in the pretty much the medial aspect of the frontal bone next in our classification we're looking at the cartilagenous uh joints and so here we have two types we have a synchondrosis and we have a symphysis so synchondrosis pretty easy condro means cartilage and so this is where we have a two bones that are being bridged to one another through cartilage and we should not have movement at these particular joints so again this should be synarthrotic it's a Sy Tove at these and a perfect example would be the epipal plates of cartilage that we see um within especially long bones during development through childhood because if you think about it that plate of cartilage is separating portions of the um epiphysis right from one another the distal and proximal uh portions of that bone and then you have the diaphysis and then another plate of cartilage remember at the other end of that long bone but again the fact that we have that plate of cartilage separating portions of the bone makes it an articulation makes it a joint now a symphysis is where we're going to have a very substantial wedge of cartilage that is going to be between the two bones allowing a little bit of movement so again examples of this we said before the pubic symphysis where you have that wedge of cartilage between the two uh coxal bones anteriorly and then we have the intervertebral discs now these are those discs of cartilage that you're going to see wedged between adjacent vertebrae now we have our sovial classification remember all sovial joints are going to be diarthrotic meaning they're freely movable you would die if you didn't have these because you wouldn't be able to move move to your resources to your shelter to getting food now there are going to be um numerous types that we will later on in this uh in the presentations get to but when we look in essence at a sovial joint considering it structurally they all are going to be encapsulated so we're going to have a like a two layer encapsulation around the ends of them and this then is going to have where the ends of the bones are going to be capped with articular cartilage for a very specific purpose and then we are going to see that this capsule is going to be filled with sovial fluid and that synovial fluid is going to have a few functions one of which is going to be lubrication so that we have a smooth motion between those two ends of Bones as they are being pulled by muscles to create movement as we stated before four sovial joints being that they are also diarthrotic they're going to allow for a wider range of motion than any of the other joints that we've also looked at now they are going to be surrounded by a two- layer capsule the outer layer is going to be fibrous tissue in nature now the interlining is going to be comprised of sovial membrane now the sovial membrane is pretty much made from aial or tissue with this kind of incomplete epithelia lining because the aerial or tissue is going to create sovial fluid that is going to seep into the joint cavity and this is going to provide three things for this synovial joint so first and foremost what we're going to see is that I mean really there's not a lot of sovial fluid in here maybe about 3 milliliters and it's kind of the consistency of like um an egg yolk or even like molasses and so first and foremost it's going to lubricate this this is going to ensure that as those bones get pulled by muscles that they don't cause friction or grind upon one another they're going to have a nice gliding Motion in addition to this we're also going to see that as this as this movement occurs between these bones we're going to have that fluid um be able to lubricate this and when we bend that joint if we cause this movement that's going to squeeze that sovial membrane causing that sovial fluid to be created to kind of get squeezed in and out so we're getting a circulation of that fluid and because it contains nutrients and it'll absorb waste this is how we're able to nourish all of these structures within this capsule because obviously we can't have blood vessels in here we'd be crushing the blood vessels every time these bones moved against one another so we we then kind of you know trade this out for the sovial fluid that'll serve that purpose so then otherwise inside this capsule these structures are avascular there no blood vessels in here we're dependent upon the sovial fluid for that nourishment distribution what's really cool too is that the Caps of articular cartilage on the ends of the bones those like to absorb the synovial fluid as well and so this way every time you're using these bones again you're causing the slushing around of that fluid which again is going to lubricate as well as distribute the nutrients and then also what we see is that when we increase pressure on like weight with weightbearing exercise on these joints so if you're thinking about like your hips and your knees when you're running what's going to happen is that the sovial fluid is actually going to get kind of thicker and provide more of a shock absorption uh capability to it so again this fluid is I mean if you think about it pretty dynamic in nature with the purposes that it can serve within that synovial joint so this is why it's really important you know you know you hear all this about you know being active having an active lifestyle and lots of movement but I mean it is for the purpose of being able to swish that synovial fluid around for the purposes of lubrica nourishment distribution as well as shock absorption there are a couple of other features that we see Within These sovial joints we refer to these as accessory structures that are going to help uh maintain the Integrity of the sovial joint so in some areas some sovial joints um with this you're probably thinking the knee most likely we have what's referred to um you can have meniscus present or the plural is minisi or miniski um now this is a pad of fioc cartil that is going to act as like a more substantial cushion uh between where those bones articulate so this can also um in a way almost manipulate the nature with which the two bones articulate with one another and we'll take a look at that when we look at the knee joint we also have distributed throughout some of our sovial joints little fat pads now this is comprised of adapost tissue that essentially acts like a packing material so that when we move this synovial joint we're going to have this kind of fill in those space is kind of maintaining the Integrity of the joint as it's moving um and usually these fat pads are superficial to the actual uh capsule and then we have ligaments and remember ligaments connect bone to bone we can have ligaments that are dispersed within the joint capsule and we can also see them distributed outside of the joint capsule in an effort to stabilize the joint and so this is having these ligaments is going to help determine in essence what movements this articulation can and cannot do then we also have little fluid filled Pockets little fluid filed sacks called bers now bers are going to be in areas where we have um you know maybe a little bit of friction uh between bony and soft tissue material and so in this way we're going to reduce that friction and we're going to be able to absorb shock in areas where we might have some weightbearing nature during the movement of the joint uh these little fluid filed sacks are filled with sovial fluid and sometimes you will even have bers develop in areas where there's an immense amount of friction where we didn't naturally have a Bersa and so we actually refer to these ones that get created because you know the body's adaptable and we want to make sure that we're protecting the structures um of the joint these are referred to as adventitious bers something a little separate from that tendons these are not ly like considered anatomy of the joint per se because tendons connect bone to muscle however we do make some references to them when we look at some specific joints because they are also going to do similar to the ligaments be able to kind of Define the movements and the range of motion that can be permitted at a particular joint so a picture is worth a thousand words um so I figured we could go through this a little bit now remember this the capsule is going to be two layers here we have the fibrous portion and then the sovial membrane so this grayish material here is going to be that fibrous joint and this right here this ligament that you see outside of it would be an extra capsular ligament you see another one over here if the ligament was within the joint capsule it would be considered an intra capsular ligament so this example right here that you see of the knee joint we have what are referred to as cruet ligaments that'll be within that joint capsule to Li the amount of anterior and posterior Mo motion of the tibia so when we look at our more simplified um anatomy of the sovial joint we also see that we have articular cartilage capping the ends of the bones to ensure we have a smooth motion between them and we protect the Integrity of the bone tissue itself we are also going to see here that we have the actual space which is the cavity this is the area that we would fill with sovial fluid to lubricate to nourish and to act as shock absorption that fluid is made from the synovial membrane and then it is pushed out with movement through the cavity again to be able to fill that space in between when we take a look at the capsule overall though the periosteum is going to pretty much become the capsule in essence the nature of the periostium we're going to see histologically the tissue will transform if you will into the fibrous nature of the um outer capsule