Bone Classification PDF

All right, so what I'm going to discuss today are the classification of bones, and they're primarily the main way to classify the bones is according to shape. So classification of bones based on shape, okay. So there are six main categories, but in actuality out of the six, four of them are the big...

All right, so what I'm going to discuss today are the classification of bones, and they're primarily the main way to classify the bones is according to shape. So classification of bones based on shape, okay. So there are six main categories, but in actuality out of the six, four of them are the big categories. but I'll go ahead and start with one of the smaller categories and these are these are sutureal sutureal bones and for sutureal bones as this word implies they are they are bones that are going to be found in the sutures of the skull so sutures are joints where two bones meet in the skull and so these bones are are not really counted in the 206 bones that we have in the in the body because they vary quite a bit from person to person. Some people don't have sutural bones, some people have a lot of sutural bones, and so again it varies from person to person. But if there are sutural bones, most of those bones will be found towards the back where the two parietal, so I'm not that great withdrawing but like that let's say these are my two parietal bones and then this is my occipital bone back here so these are the two parietal and these are occipital. This suture right here is called the lambdoidal suture, lambdoid or lambdoidal suture and if you're going to find sutral bones this is where you're going to find in between these three bones and in the back of the skull And in lab, we do have, of course, human skulls. And there are some skulls that have sutural bones. Some of them are quite big. So these sutural bones can sometimes vary in size from being like the grain, like of a grain of salt. And then some of them can be quite big, like maybe the size of a quarter. And so the ones that we have in our lab, some of them are actually quite big, right? So, again, primarily going to be found in the back between these three bones. But in one of our skulls in lab, they actually have one in the front, which is quite unusual. And it's only one skull that has that. So they can be found anywhere, anywhere two bones meet in the skull. But again, it varies from person to person, whether they will be present or not. So that's one bone that you will have and again they're found between sutures. Another one that you're going to have, I'll do the other one which is not that common, they're called sesamoid. Sesamoid bones and these sesamoid bones are bones that are going to be found like within joints and we do have one and And it's actually a relatively large one. So maybe you may not be aware, but the patella, the patella, which is your kneecap, is considered to be a sesamoid bone because there's a lot of connective tissue around it. And it's not necessarily surrounded by an entire capsule, but it kind of is surrounded by a lot of tissue that's associated with the joints. Now occasionally people sometimes do have sesamoid bones in their small joints and and so sometimes you may feel in a person that you there's like an extra hard little piece of bone in there. These sesamoid bones are very very common in dogs and cats in the joints of their paws. So for them, they almost have one where each of the bones meet. And again, they're very small. For us, we primarily just have the patella, but for a few people they may have some sesamoid bones in their hands and possibly in their feet okay so these two are not that common the next four are very very or a lot more common I should say so I'm going to start with the let's start with the long bones and so for long bones they are classified as long bones if they are longer than they are wider right and so for most people they don't as the humerus that's here, the radius and the ulna, definitely the femur, those are long bones. But even these little small ones that are found which are part of the phalanges that form your fingers, each one of these is considered a long bone as well. So again, the criteria is just that it be longer than wide. So even though they're small bones and they're not very, very long, they are still classified as long bones and one easy way to remember where most of them are is you're primarily going to see long bones in the appendages so starting from the from the humerus down all of the bones in the upper appendage are long bones with the exception of the carpels that's those are the only ones that are not long bones. So the humerus, the radius, the ulna, metacarpals, and all your phalanges, they are all considered long bones. Okay, and then as far as the lower appendage, again almost the same thing with your lower appendage, it starts with the femurs, and for each of the femurs if you go down, all the lower appendages, long bones, with the exception of, of course, the kneecap, which we just talked about, the patella, and also the tarsals, which would correspond to carpals. So those are not long bones, but everything else is considered a long bone. So again, long bones are primarily seen in the, I'll just go ahead and put it in here, they're primarily seen in the appendicular skeleton okay so again mostly your appendages but does not include the girdles does not include the shoulder girdles and the pelvic girdle but everything else is pretty much long bones okay and then the next one are going to be your short bones and for your short bones they are I guess described as being cube-like and in some cases they are cube-like but in other cases they're more of a little bit not not that square a little bit more irregular but those are my short bones and there's really only two places where you're going to feet where you're going to find these short bones and the only places where you have them is in your wrists so the carpels are short bones and also your tarsals on your feet are short bones and that's pretty much it right so if you were to ask them which skeleton do you find them of course they would also be part of the appendicular skeleton okay and then the other type of bone based on shape are my flat bones flat okay and for my flat bones as the name implies they are going to be thin they're going to be flat thin bones and flat bones are primarily going to be seen in the skull so many of the skull bones like the frontal bone, the parietal bones, they are, they have flat surfaces on them. It also includes the sternum and it includes the ribs, right, so those are all examples of flat bones. And so when you think about where they are, those bones pretty much all belong to what we would call the axial than appendicular, so if appendicular are your appendages, everything else that is closed to the midline is considered axial skeleton, so most of your flat bones, I would say all of your flat bones, are within the axial skeleton, okay, and then the last category is if you cannot fit them into any of the other categories, they are called irregular and so irregular bones as the name implies they tend to have processes that stick out of them they tend to have structures that stick out of the bone and and that's what makes them irregular so examples of irregular bones for example would be vertebrae vertebrae is one vertebrae are very irregular bones. And again vertebrae are part of the axial skeleton. Okay so you could put other bones there like the teeny tiny bones that you have inside of your ear. They're all they would also be considered irregular. The hyoid bone that's right here behind your mandible could be considered an irregular bone. and then many of the bones in the skull especially the ones that are deeper they are very very irregular bones so again most irregular bones I would say all irregular bones are part of the axial skeleton so you can see that the long and short bones are part of the appendicular whereas the flat and regular bones are mostly or entirely going to be within the axial skeleton. Okay, all right, so keeping that in mind, so what I'm going to do is I'm going to be just discussing what the structure of a long bone looks like. So I'm going to look at this long bone, right, and we're going to talk about the features of a long bone so what is a long bone made of so when we look at a long bone I'll do the best my ability I'm not the best at drawing here but let's see I'm going to try to draw the femur and I guess I'll do this okay and so for this femur the first again this is a long bone it's longer than it is wide but for long bones what you tend to see in a long bone is that you tend to have like a narrow middle part right here and so this part right here, all of this right here, is what we call the shaft or we will be calling it the diaphysis. The diaphysis, so again this is the shaft of a long bone and if you look to see what what's in the shaft right in the shaft you will notice that there is actually that it is actually hollow on the inside right so right in the middle of your a diaphysis you have what we call the medullary cavity and this medullary cavity is filled basically with fat. basically with fat. It is filled with adipose tissue. I'm going to put adipose connective tissue, right? adipose connective tissue, right? And again, that adipose connective tissue, so it's because it's found within the bone, we call this yellow bone marrow. Yellow bone marrow. So the yellow bone marrow is made of adipose connective tissue. Alright so that's what the diaphis is made of and then the all the edges of around the medullary cavity so all this area here all of this is very I usually compact bone. So this is a nice thick layer and this is what's going to give strength to these long bones, okay? And then if we look at the ends of the bones, the ends of the bones which tend to be wider and you have Excuse me, you have them on both sides. These are called the epiphysis. So epiphysis you're going to have them on the proximal end and epiphysis will also be on the distal end of the bone and if you look to see what the bone looks like there is you will find a thin layer so basically what you see there is a thin layer of compact bone but most of what you see in here, I'm not going to draw anything in there, but most everything that you have in there is actually made of spongy bone so all of that is spongy bone. So spongy bone does not mean that if you push on it too much it will break and it will of course not pop back like a sponge does so it's not spongy you can't it's not it's not flexible it is delicate you can push on it and it can break but again it's got a lot of spaces in it and that's why they call it spongy bone so that's what you see on the ends of the bone. So there's two types of bone and again the diaphysis mostly has a lot of the compact but the epiphysis have a thin plate of compact and then most of the rest is going to be a spongy on the inside. Okay so the last thing I want to identify is going to be the area between these two. This is called the metaphysis. The metaphysis is just the area where the epiphysis meets the diaphysis, so again you have one on each side. You have an epiphysis on each side, you have a metaphysis on each side, and that's where you expect to see the epiphyseal plates, or at least close to it, which we'll talk about later on, but again those are the main parts of a long bone. Those are the parts that you have to identify on a long bone. And I forgot to mention but anywhere you have spongy bone you are likely to have red bone marrow. So I'm going to put my red bone marrow in here. And red bone marrow is a site for red blood cell production. It's not the only site but this is a major site where blood cells are formed. You form both your red blood cells and your white blood cells in the red bone marrow. So maybe you have heard that if a person has leukemia, like a child when they have leukemia, they may require a red bone marrow transplant to try to give them normal healthy cells to replace the cancerous cells that they have developed. okay so again that's the the red bone mirror so that's the structure of a long bone this is what a long bone looks like right now if we were to look at a short bone to see what a short bone looks like I'll just try to use a different marker here so for a short bone basically a short bone looks like this right here right a short bone like the carpels and the tarsals that you have they and actually that would also even be true for the sesamoid bones. They have a thin layer of compact on the outside but the rest of it is spongy on the I'm just gonna say inside. So thin compact bone outside whereas you have spongy bone all on the inside. So all of this right here is filled with spongy bone. So it almost would be like a the epiphysis of a long bone. The structure of that bone is similar to what you might have in short bones. So I mean you could with these short bones because it's all spongy on the inside if you were to take a hammer to it put one on the table you would shatter it to pieces so so again they're not as strong as the the compact bone that you have in these long bones okay so that's the structure of a short bone now for the structure of a flat bone for the structure of a flat bone what you're going to see is that it's like a sandwich. You have a sandwich, okay, where on the outside of, or like what you might consider the bread of a sandwich, this is all going to be compact bone, right, but in the middle between the two layers, so this area right here would be spongy bone okay so again a flat bone is just made of two layers of compact on the outside with a layer of spongy on the inside and later I will be talking about the development of bone and the way you develop these long bones is different than the way you develop these flat bones, and therefore there is a bone right up here in the shoulder girdle, which you probably know, but that bone is called the clavicle, right? And the clavicle is going to be considered a flat bone. The clavicle is not part of the axial skeleton. the clavicle is part of the appendicular skeleton, however the clavicle, if you can picture what it looks like, it tends to look long but the only reason they don't classify it as a long bone is because if you cut through it you're going to find this structure. It's going to look like a flat bone on the inside. You're not going to have that medullary cavity like you have in long bones but instead you're going to have spongy on the inside and you will have compact on the outside and so the way this bone develops is uh the way the clavicle develops is similar is the same way that you develop flat bones so it is a flat bone um but it does look like a long bone okay all right and then the last one irregular bone so i'm not going to say much about this one because for an irregular bone, for an irregular bone basically all you have is kind of like starting off with a and again it depends on the bone you can almost start off with something like a like a like the patella or a short bone or something like that and then you're just putting processes on it right like you for this would be the vertebrae right so of course it's got a hole in it like right here right so again it's like starting off with a short bone but then you stick processes on it and again it just depends on which bone you're talking about how much spongy how much compact you're going to have so again this part right here is mostly spongy and then at the edges of all of these they're all compact bone with a little bit of spongy on the inside so again irregular bones they kind of have different shapes so it would depend on on the processes that they have how much spongy and how much compact you would have in those cases okay all right so that's it for this one this is just describing the classification of bones based on shape and then just taking a look inside at what kind of bone tissue you have in these types of bones. Okay, thank you.