so when we think about classifying bones we talk about the gross anatomy and general features of Bones and there's several different ways that bones could be classified you could classify them regionally you know bones of the apendicular skeleton or axial skeleton we could classify them by their overall shape and a lot of times we do both so we have to be able to of move in between these categories and understand why a bone could belong to both like for example the apendicular skeleton as well as be called a long bone so different ways of classifying them so first off by location we could talk about where bones are located in general like where in the body do we find them so one main category is axial and bones of the axi are just located along the axis the central Axis or midline of the body so if you think about the human body we're we have long bodies tall bodies anyway and so we have sort of a central axis that goes down the center and we have bones that are found in that Central axis region on the other hand we have apendicular skeleton and these are bones of the appendages so these would be limbs bones are the appendages limbs so let's talk about some examples that we would find in the axial and apendicular skeleton now that we kind of see how this is very broadly classified so axial would include bones of the skull because that's definitely along the midline of the body um bones uh so for example vertebrae those are definitely along the midline of the body um other things that we could think of things that extend from the vertebrae for example uh would be bones of the thoracic cage and so when we think about the thoracic cage that would be forming the thoracic cavity so we're looking at ribs sternum all the things that you could make a case for are either found directly on the midline or extend from the midline like ribs for example so these are things we find directly in the central Axis or extending from the central axis of the body when we think about apendicular some of this is really obvious and then some are are not so obvious there's some that fit like you could see it go either way so I always like to be very um clear with people like where some of these bones um sit so obviously if we're thinking apendicular we're thinking limb bones so that could be limbs uh you know we've got the pectoral limbs those would be arms more appropriately known as pectoral Limbs and the of course the um pelvic limbs so legs so that makes sense arm bones everything associated with hands limb bones leg gums everything associated with feet but what about girdles you ever heard those terms before girdles for example where does the scapula and clavicle fit in these categories here scapula and clavicle you can make a case either way couldn't you like well clavicle kind of extents in the midline but it's also associated with the limbs so anyway when we talk about these collection of Bones the pectoral girdle I if you've heard that term before pectoral girdle it's actually part of the apendicular skeleton so attaching the limbs to the body that's what girdles do so we can also in this list here put the bones of the um pectoral girdle again a girdle is what attaches the limbs to the body and so that would be uh clavicle and scapula and then we've got the um pelvic girdle and that attaches the legs to the body so here we're talking about you know bones of the pelvis but more specifically um the isum and the ilium isum and ilium so when I talk about girdles that's what I'm talking about girdles just attach limbs to the body it's good to be clear because I always remember when I was learning this I was thinking it really could go either way some of these are kind of technically attached to the midline how do you know and so anatomists have sort of decided as a group this is how we will go for so very broad ways of classifying bones by location axial and apendicular but normally when we talk about bones we're going to talk about bones by shape and so with in the axial and apendicular skeleton we find bones that are classified by their overall shape so when we talk about shape overall shape not necessarily size so see what I mean by that in a moment so overall shape of a bone not necessarily its size sort of its overall orientation I guess you could say so the reason why it's important to say overall shape and not size is because there's some Oddities we're going to see um for example we'll talk about long bones you can kind of see them peeking out through that piece of paper but long bones are found obviously in the limbs apendicular skeleton femur humoris those are long bones but interestingly fanges proximal distal middle fangi those are pretty short overall but they're still classified as long bones because their overall shape is they're longer than they are wide so that's what I mean we have to talk about overall shape and not necessarily their size so the first category that we'll talk about um do a chart here and if you have this printed you can sort of follow along I've given you kind of a um a shape hint any way or sort of a a representative of that particular category when we think about shape let's talk about long bones these are the most familiar and so with long bones we can see that they are generally longer than they are wide so length much better than with that's how they get their name so the femur for example which is what you see here that makes a lot of sense when we think about long bones they are found as part of the apendicular skeleton long bones are generally associated with or player roll in Locomotion which just means movement and other features or functions include housing a pretty large amount of marrow so large long bones like the humorus the femur the tibia um they have the luxury of space on the inside in the center here and that's going to be full of marrow red marrow or yellow marrow depending on the age and health status of the person I just like to be clear about that because other bones that we're going to talk about they don't have the luxury of space and so while they certainly do contain marrow it's not in this nice dedicated cavity that marrow or medular cavity is only something we see in large long bones we don't even find it in like the fanges the smaller flat long bones um so it's only these large limb bones really that have that dedicated marrow uh cavity so when we think about marrow cavity there's a couple words I want to introduce these are kind of they sound different but they mean the same thing and that can be confusing so when we think about housing marrow we could talk about that dedicated space we could call it a marrow cavity we could also call it a medular cavity so these are the same thing and they would refer to you know if you could look inside of this long bone they would refer to that sort of central seemingly Hollow cavity in preserved bones but marrow or medular cavity both of those are correct so long bones pretty familiar to you I think is what most people think of when they think of bones but there are lots of other categories let's talk about short bones so notice short bones um they are fairly cuboidal they are about as wide as they are tall they are also part of the apendicular skeleton limones and we really find them in areas like the carpus and Tarsus what are these more commonly known as regions carp say lot carpal is known as the what region or the wrist yep good so you could say wrist bones and that's what most people would know them as but of course you need to call them carpal bones and that means tarsel are the what ankle bones so that wrist and ankle it they're pretty strong and of course you can fracture them but the reason why they're pretty strong is because they are full of of stacked rows of these short or kind of cubil shaped Bones the purpose of these whatever shape they are and usually as wide as they are T CU like they are great at providing stability they are tightly knit together with ligaments so ligaments connect bones to Bones tendons of course connect muscles to bones um but they are really together in a very stable structure and they act almost like Columns of stabilized bones move a little bit but they're really great at providing kind of an anchoring sight for other areas that may move a lot so most of them are like this the only exception is the calanus or calcus what is that more commonly known as calanus bone so that's the heel bone and if you think about the way the heel bone is shaped If You observe that in lab just you know maybe looked at the skeletons that we have up there they they don't look anything like parcel or carpal bones but they truly do fall into the short bone Cube like um sort of category so calcus anous that's the heel bone still considered a short bone and if you think about it it really is good for stability it really has a great ability to do that um so if we were to sort of You Know sketch this out a little bit more in the wrist or ankles again you'd see sort of stacks of short bones and I'm not going to try to draw these in any way that's anatomically accurate I just want you to understand that when we put stacks of these short bones together and then we knit them together with ligaments which is what I'm going to do now it's going to be a light blue that's a pretty stable area it is technically a joint because you have two bones coming together but they don't permit a lot of movement um so also just a couple words that I mentioned that I want to make sure we're clear on when I talk about a ligament because we'll see this when we talk about structure of the knee which is coming up uh a ligament is some sort of connective tissue that connects one bone to another bone it's bone to bone and that would be different than um a tendon so I'm not going to write tendon on here because there's no tendons here um I could write it up here though so if we wanted to compare a ligament connecting bone to bone to a tendon a tendon is um a connective tissue type or classification that connects muscle skeletal muscle to Bone so last week Thursday when we talked about getting a skeletal muscle group like vasus lateralis or a gluteus muscle to connect to a bone you know we'd have skeletal muscle out here I'll sort of make it strided looking um but that muscle does not directly connect to Bone that's the job of a tendon and we talked about a precise area where that tendon interdigitates with that compact bone what was the name of that area name of the area where tendon interdigitates the bone enthesis yeah enthesis so tendons and ligaments do serve similar functions but they are also quite different um ligaments will stretch a little bit more than tendons stretch too much but you can stretch them a little little bit before you damage them all right let's move on to our next category of bone and that's a flat bone so a flat bone flat bones are mostly found as part of the axial skeleton so Central they are generally quite thin there's some called like a a membranous bone uh they are often curved what do you think the significance of having some sort of curvature is we don't really want bones to be flexible need to be somewhat rigid but any structure if you think about some sort of architectural feature art what's the purpose of an arch in a doorway or an arch to a bone or support yeah it's strength so a curv structure is always better at providing resistance against Force that's why a lot of doorways like ancient architecture were arched because the more load you put on it the more strong that Arch got and so we can sort of think about bones here as being sort of actually architecture borrows from Bones the other way around but often curved so you can have a fairly thin structure but it's actually pretty strong because of that curvature in general when we think about flat bones they usually provide protection to delicate Vis what is viscera again common word for what organs yeah like the brain the brain is really well protected by flat bones of the skull um the ribs those are flat bones and they protect delicate viscera of the thoracic cavity like heart and lungs so interestingly even though flat bones may be pretty thin structurally they are the site of homat poesis throughout life so first of all can you remind me what hematopoesis is what does it do produces more more blood cells yeah so hematopoesis if you look at the prefix hemato he that should make you think of red that is what it means so hematopoesis is the production of new erthrocytes it also produces new Lucas sites so blood cells and interestingly this is the site of hamat poesis throughout life and that's different than if you were a juvenile child where would you also find hopis occurring mention this briefly on Thursday inside all bones that's right inside all bones but by the time you're an adult you don't need that many red blood cells you usually don't need as many white blood cells barring any infection and so we kind of see a retraction of this process of homat poesis from long bones all bones really uh to just major large flat bones like bones of the pelvic cavity or bones of the pelvic ilium and isum so hematopoesis throughout life so just like to mention that because when you look at something like this you think well protection that makes sense but interestingly physiologically very very important as well throughout life all right let's move into sort of our Strange bone category so these three are fairly common we'll find them in big numbers in the body the next two less common oh I forgot to ask this I said axial mostly can you think of a bone it's flat and it's part of the apendicular skeleton flat bone part of the apendicular skeleton scapa scapula yeah great job scapula scapula is a flat bone and it is technically part of the pectoral girdle which makes it part of the apendicular skeleton great job there so these are the common ones and then we get to the um sort of oddball category still important just less known we're going to talk about the sesm moid bones seso these get their name because the early anatomist thought they look like sesame seeds and they named things for what they found common in their environment this would be a patella the kneecap sesamoid bones are found as part of the apendicular skeleton knap obviously part of the limb bones generally sesamoid bones are embedded within soft tissue usually within soft tissue so sometimes they're hard to find upon dissection because they can be embedded in soft tissue the knap you could probably find that without too much trouble wherever we find them their job is to act like a pulley system and they help alleviate stress and friction on tendons where tendons connect muscles to bones what is the problem with creating friction what does friction itself create heat and heat is very dangerous to soft tissue it's very damaging and so we believe that sort of invention The evolutionary um um sort of arrival of these Sid bones was because humans mammals got larger and they moved around a lot and they had really heavy skeletons and a lot of muscle pulling on those bones and so this acts as kind of a pulley system so if we think about how the patellar bone would function as part of the patellar tendon now that we kind of see this we could sketch out its rough anatomical position to other parts of the limb so I'm going to do the patellar tendon up here and the patellar tendon um helps keep the quadricep muscles nice and elongated and then down here we'll see it continue and help that Pella attached to the tibia and probably the fibula a little bit down but no notice we don't have a tendon that has to span that knee joint that would be a lot of friction a lot of friction on that tendon so if we put a bone here we don't have the rubbing of soft tissue over the edges of the bone the end of the femur in the beginning of the tibia that's too much tension and stress and friction so that helps sort of alleviate that we can also wrap bones in a slick cartilage and that reduces friction as well so the P tendon greatly benefits from this um when we think about other areas of the body where we find sesamoid bones it's probably something we'd find in all humans kind of a debate so I want to say very you know I like to qualify it with probably um this the patella is the most well-known but there are tiny little seso bones under the um the big toe joint actually so if we think about where the end of the metatarsal the foot bone just going to draw sort of the end of a metatarsal joins that first toe bone big toe bone this is a long bone and also a long bone here they're kind of pointed on the end but right under here we can find two little seso bones so this would be metatarsal this is a fangi so that would be approximal anyway right under where this toe foot bone meets your first toe bone that proximal fangi there there are two little bones here and we believe they are likely present in all people although when they have looked for these and like just using cadavers they didn't find them in all people but they are present in a good portion of the population the reason why I bring this up is this is kind of right under the ball of the foot area everybody knows where the ball of the foot is right and um ladies if you've ever worn high heels at the end of the night your feet are killing you and this is usually a region that really hurts and you can actually fracture these tiny little seso Bones by wearing high heels and walking on like really hard concrete um and you can also fracture them just from like overuse like running with por shoes on concrete the reason why I bring this up is this is often an area that is damaged but because it's embedded in soft tissue it doesn't then they're tiny it's really hard to pick up on X-rays and so you could actually have a fractured Sid bone there producing a lot of pain but hard to diagnose uh and so I just like to bring it up because it's just a weird thing if You' ever hurt that area you know exactly what I'm talking about um so just something to think about sort of new discoveries in anatomy they happen occasionally that's for sure um okay other weird categories of Bones include a category called irregular bones and this truly is kind of a catchall for bones that didn't fit any other category in the body um so we generally find them so far anyway in the skeleton part of the midline they get their name because they have no defined shape they are truly regular in shape lots of different functions but generally we're looking at either providing sort of a like a base to support other structures or protect delicate viscera what bone do you think this is give you a hint it's found in the cranial region it is spinoid yeah good job this is a spinoid bone very irregular lots of different parts sort of forms the base that uh the the cranium sits on also forms part of the facial structures lots of different stuff here um very irregular definitely protecting delicate viscera some irregular bones like the sphenoid or the ethmoid bone are ptic what does that mean [Music] pneumatic this word pneumatic the p is silent pneumatic what does that mean so pneumatic means it contains air pockets and so if you were to cut into a spinoid bone or ethmoid bone you'd find pretty big pockets of what look to be empty cavities they contain air so pneumatic contains air pockets that's on purpose what value could air pockets provide in a bone oh so yeah if you had sinuses there um sinuses so if we think about the frontal bone they have sinal sinus cavities those are um sometimes filled with mucus but hopefully drain out what something like a spinoid bone now full of air pockets get lighter lighter yeah it's a reduction in weight so this weird thing we have on the top of our cervical vertebrae weighs about eight pounds like a bowling ball and it is awkward right like if you think about all the ways you could hurt your neck like Whiplash or something it's because you got this giant bowling ball that sits on a little tiny pedestal and so we believe any bone that could reduce the weight without giving up strength was really beneficial and so this these air pockets definitely reduce the weight of the bone and they also help with um sound resonance which helps produce different tones of the voice so reduction in weights resonance and maybe projection of sound so it's a strange thing to think about bones purposefully have air pockets purposely have air pockets all right so that is um of a tour of the bone before we go farther here's a question for you humans are born with about three in bones but you only have 206 by the time you're an adult why what happened Fusion somebody said it so you have a lot of bones that fuse especially in the skull region um you also have uh bones that come together in the apendicular skeleton just to resemble like one bone give them one name and so we actually I don't want to say lose bones but due to Fusion as you age you actually end up with fewer bones so it's an interesting thing to think about before we leave this I wanted to um put into perspective some of the things I've talked about by going back through this and introducing examples of real bones that fit this category using um My Strange collection of Bones so um you're going to see these off and on I have a lot of strange things in my office so why not get them out um I've introduced some of these to you so anything about you know long bones again these are not human but I think they they serve a good role so here's a great example of a long bone a femur and a femur and we can see definitely longer than they are wide we can see a great area inside which I'm not going to cut it open we' see a really nice dedicated marrow or meary cavity and as we'll see in a moment this has some really interesting external features like tro caner Condes great for muscle attachment or joints so we're going to see these have even more features externally that we're going to talk about here uh in a moment uh for short bones I do have a collection of short bones I'll show those to you as well so short bones I have a nice collection here this would be the hind paw the Pez not the manace of a cat and so we can see here very similar in humans we have a nice collection of stacked short bones and that provides a lot of stability to these metatarsals and so these are connected with ligaments as I said earlier and those ligaments provide stability we hope they don't stretch too much um but they should stretch a little and so if you turn it over you can kind of see what I mean about stacks of small bones and so humans would be fairly similar in that respect all right let's talk about flat bones flat bones I got several examples of that we could look at the scapula and so the scapula very um strange looking bone it's got this nice H Crest here great for muscle attachment but if you look at it how thin is that that thing is super thin and so really quite a good example of a flat bone moving on we could talk about the patella and yes of course I have the patella of a cat why wouldn't I um but here we go it is um hard to see in the resolution here but definitely sesm moid shape it is kind of looks like a comma that's another way to look at it and then finishing off my collection I have um half of a cat skull it had a splitting headache um but anyway if we look at this we can actually see quite a few of these other examples um in this for example pneumatic bones so down here we have those irregular bones you know I talked about the sphenoid and the ethmoid bone this has been cut on the mid sagittal plane so right down the midline but we can see the details of that and I wanted to talk about how many bones have air pockets so frontal bone definitely has air pockets for sinuses somebody over here mentioned that if we look at this ethoid bone here that thing is full of air pockets as is the sphenoid bone and if you think about in total that really does reduce the weight of this skull and probably helps with resonation for sound we can also see just how flat the skull bones are very very flat very thin but that curvature really provides a nice bit of extra strength without weight so there you have it real examples of Bones any questions on this before we move on actually I'll give you about a 3 minute break 310 and we'll come back 310 really [Music] Grand very spe [Music] all right all right welcome back mve to external and internal structural details of long and flat bones let's talk about long bones I'm going to use the femur as an example I think that is a great example people are familiar with the femur it also has a lot of features that allow us to sort of understand a lot of different things about long bones femur kind of has it all as far as I can tell um um so I want to talk about two things um when it comes to long bones we're going to talk about external features and regions and then when we get done with that I'll come over here and talk about internal features and regions but these are all about long bones I will then at the end of this particular set of notes compare this to a flat bone and we'll also pick up a little bit of information about synovial joints so um usually if we study the features of long bones and flat bones we can understand how the other categories of Bones work because they're built fairly similarly in my opinion long bones and flat bones sit two ends of the spectrum so if we understand those well we can understand the features of other bone categories as well so we're going to start on the left hand side and specifically look at the external features in regions of a femur so did I bring one yes of course I did it's not from a C this would be heck of a cat um but this is from our Bine friends uh BOS horse um so when we think about a femur you know this is a fairly obviously fits the description of a long bone but what we're going to see here is there's a a lot of features to this you know there's a lot of sort of these projections or kni extensions on the proximal end on the distal or farther away from the midline we also have have bony projections and features and all of these mean something you can even see very very detailed um examples of like features on the on the shaft of the bone the diaphysis Linea aspia we can even see where the nutrient forment which is where a large blood vessel would enter so these bones tell us a lot of Secrets uh and so I always like to help you understand why are they made this way and they are fairly well conserved as far as shape and overall function amongst the mammals so I will refer to this off and on uh in our lecture when I think it is appropriate but uh it's up here after class if you want a picture of that feel free um it is very heavy though so I think if you you know really think about how much effort it takes to carry a bone around you can start to see any adaptations that allow a bone to do its job but be lightweight lighter weight anyway highly favored um by natural selection so we're going to be looking at this left hand side here if I can get this to cooperate we're going to look at external features and regions of our long bone so if you have this printed you have a sort of a picture of a long bone um and I'm going to sort of go through the different parts of this bone there are a lot of different regions to a long bone and they all all do different things so the first part we're going to be starting at the top end of this long one this femur so proximal means closest to the sort of trunk proximal closest to and so we have what's called technically the proximal that is pronounced eposis or epifisis both are correct both are correct epiphysis or epifisis if you put your emphasis on the right wrong cabable it sounds very different doesn't it so they're both correct so you just have to kind of be familiar with how they might sound when we think about this this whole bracketed area is the epis Oris it's got a lot of features it has a unique structure and that's because it has several different jobs one is articulating with another bone what does it mean to articulate with articulate what does that mean yeah that's right I like yeah this is a class appropriate hand gesture so thank you I like that so they Bend or move in relation to each other they articulate they Bend it's an articulated skeleton it has joints and so they can articulate move in relation to another bone that itself is a challeng having a large mammal humans are fairly large mammals that can support this much weight and move pretty fast like that's a lot of acceleration and shearing Force to put on a skeleton the joints really suffer um and so having a a really great site where a bone can articulate quite strongly with another bone but also have flexibility of movement that's a challenge and then we'll also see in the proximal an area for muscle attachment so when you think about these bony extensions this has to it's got the femoral head to be a side of articulation with the hip socket otherwise as the acetabulum we also have this sort of Nai extension up here called the greater tranter I'll write these out for you in time but I'm just sort of illustrating when I'm talking about side muscle attachment whenever you see a really big knobby extension it's not part of a joint capsule uh you can pretty much bet it has something to do with mus attachment skeletal muscle attachment so what these bones have is basically a projection that increases surface area which allows more area for that tendon to interdigitate at the enthesis and provide a side for muscle attachment on the surface of this bone we're going to find two outer coverings or um sort of membranous um material we're going to see that in the EP we'll see either connective tissue remember CT stands for connected tissue or we'll find perio bones are always covered with either of these two a bone is never going to have just sort of a bare surface we would never see in a living human or animal a bone with no covering on the surface of any bone we're either going to find in a joint region so this would be it stifle or knee down here this would be the hip socket we would either find in the joint regions articular cartilage which reduces friction and then that gives way to the rest of the bone which is covered with something called periostium so again bones are never bare like this they are always covered with one of those two things but not both you can't have both in the same region you either get articular cartilage in joint areas or the rest of it is covered with periosteum I'll explain the value of both of those tissues in so when you think about something like this this is um the opposite limb of what I'm showing you here but you can see we've got this huge tro cancer this giant knob here that's for muscle attachment and the surface is quite rough really helps with that muscle attachment the femoral head which is where the hip socket would be very smooth it looks like it would articulate or rub easily in a joint socket and not cause a lot of friction so this is obviously too big to fit under under the iPad that's why I'm holding it up um but there's a lot of similarities and when you look at really large bones like this really highlights the value of of these particular features so having said that I'm going to go ahead and sketch in some details that I've talked about so I kind of made a bulleted list of things that are unique in this area I'm going to continue with sort of illustrating or sketching out the details that I talked about so here we're going to see this is the head this is the the femoral head and it is covered with a type of connective tissue so I do sort of a glassy blue for this and in living bone tissue or fresh tissue it actually does look like a glassy blue this is called articular cartilage um and it's because it is in an articulation which means another bone would be nearby so I'll just sort of draw in sketch out the um other bone that this would be part of so drawing part of the um isum here hip socket so somewhere over here we'd have another bone and I'm just going to bones are always compact on the outside sort of spongy on the inside but what you're drawing is the hip socket so this would be the isum and this is our compact bone same even though the isum is not a long bone it's got the same structural details compact on the outside spongy on the inside it's just kind of a review but in this hip socket we have two bones the femoral head and this socket here of the isum that could technically rub on each other and that would be pretty bad you can imagine what that would feel like that would lead to osteoarthritis quite quickly but in a health joint we're going to see that both of these bony surfaces are covered with something called articular cartilage and articular cartilage is found in articulations where tub Bones come together articular cartilage is more appropriately called articular cartilage is kind of a colloquial term just describes its its location it is a specific type of connective tissue and that is hyolin cartilage hyolin cartilage Highland carage is a particular type of CT and in fresh tissue it looks sort of like this glassy blue it's actually kind of pretty um but it is of the different types of connective tissue H and cartilage is the most resistant to rubbing and friction most resist so it's a great option to put here most resistant to rubbing and friction Highland cartilage in addition to being resistant to rubbing and friction is left over the remnant of the fetal skeleton so long ago any bone cat bone human bone cow bone they all started as a Highland cartilage model during fenal development and as you age that Highland cartilage is mostly reped tissue compact bone for example except in regions where we have joints and this is a remnant of your Highland cartilage from your fetal days the reason why I think that's significant is because this has to last your entire life it formed during fetal development it is a remnant of that carbage that lasts your entire life and puts up with some of the most abuse that the human body can get if you think about what people do to their joints right whether you're in sports whether you're just a clutz doesn't matter like joints are easy to injure in addition to being really great at resisting friction of heat coming from the fal skeleton having to last your entire life Highland cartilage is avascular what does that mean avascular no blood vessels what does that mean if you damage this then heal easy or not not heal easily and so here's a for those of you going to like orthopedic surgery this is why one reason why people need help this is not hard to damage some sort of fall for example in older people um or if you think about all the ways you could disrupt the articular cartilage of the knee playing sports pretty easy so it's from the fetus it has to last your entire life and it's a vascular so you damage this it is hard to fix the body doesn't have a lot of options for sort of selfhealing or repair so this articular cartilage a specific type of CT called Highland cartilage really interesting to study I'll talk more about it when we get to our schematic of the cyle or knee joint a moment but I just wanted to mention the head of the femur femur is covered with articular cartilage the rest of this femur in the epiphysis region I'm going to use orange for this next bit is covered with periostium so remember bones are never bare on their surface and I'm just going to outline it it would be covering the whole surface here but that seems like not a good use of time to color that but if you want to you can the whole femoral head will be covered with Highland Cartage the whole epices here would be covered with this tissue called Perry oium and periostium on the surface of Bones unless there's articular cartilage there is an interesting tissue itself there throughout life it acts like sort of a membranous sheath or covering on a bone and if we could peel this off and look underneath that periostium as part of the periostium we would find a layer of osteogenic cells osteogenic and that's throughout life so the periosteum has a layer of cells that are Osteo genic osteogenic what do you think that word osteogenic means Osteo refers to Bone genic produce you actually contain a layer of stem cells just on the inside of that has osteogenic capabilities that allows a bone to sort of heal superficial problems like really really small micr fractures can actually be healed by this so they'll become larger problems it also permits something called a positional growth growth and width as you age as you grow from childhood to adulthood or as an adult if you start an exercise exercise program your bones get thicker like rings on a tree they get thicker and stronger and that is due to those osteogenic cells part of your periostium so the periosteum really thin tissue but a lot of really great capabilities that are present throughout life helps you really keep those bones strong and um sort of responsive to whatever stresses may be put on them from like a like an athletic perspective so pis or epifisis depending on your pronunciation questions before I go to the next region of this long bone questions all right seeing none we're going to talk about the metaphysis and on the outside the metaphysis or metaphases depending on your emphasis of your cabble um is the outside is is fairly featureless it's going to have periostium again that that that ex extends down the entire bone until we get to the next bit of articular cartilage so still periostium uh it's a small region and externally it doesn't have a lot of features to talk about now that's going to be different internally when we take a look at the internal features but for now I'm just going to say hey between the epithesis and our next region we have the metaphysis and most long bones have two a proximal and a distal metaphysis we have two regions we're going to grow happen long bones grow at the metasis they elongate such that the head is pushed up here and down here we'll see lower regions being pushed down that's how bones grow they don't grow from the ends that would be hard on your joints because you have to grow and also still be able to move so we actually elongate from within and that happens here at the um metaphyses moving on let's talk about the DI IIs the diaphysis so long bones only have one of these which is why you don't see me using a qualifier like proximal or distal there's just one and it does represent the majority of most long bones length so if we think about this right here this has a fairly lengthy diaphysis it's fairly uniform it sort of looks Tubular on the outside kind of featureless especially right in here like there's not a lot of stuff to look at here very different than the epices and a little bit even of the metaphy sees but not a lot to look at externally all the magic here is internally um but the diaphysis does represent the majority of the length here structurally it is unique we're going to see some really cool things here that we don't see in other regions of this long bone so structurally unique if we looked at took a cut here we made a really great transverse cut here and we looked at the structure of the compact bone on the outside it's the compact bone making the walls of this bone but that is found the outside the bone we're going to see something really interesting only in the diaphysis of long bones and that feature is called an oion an oion one of the best structural developments in the vertebrate skeleton I think so within this region within the compact B of this region these osteons run the length of the diaphysis and they are little Columns of bone within a larger column of bone and structurally they resist torsion or some sort of twisting motion so to illustrate that imagine this animal walking along maybe playing basketball you know as cows do um and so walks along runs along decides to go the other way plants its foot and then takes off the other way that's a lot of torsion or twisting on a long structure and from an engineering or sort of mechanical stpoint that's failure if you twist a bone you're going to snap it in the worst type of fracture a spiral fracture imagine this thing twisting and spiraling apart really bad so as vertebrates mammals got bigger heavier moved even faster and had a lot more velocity imagine running planting that foot turning around going the other way that could twist this thing into pieces these osteons were sort of The evolutionary answer to how do we prevent rotational or torsional fractures and so osteons again only found in the diaphysis of compact bone and when we look at their structure in more detail in a few days um I want you to just think about where they're found and the rotational stress that this bone is able to withstand and not snap because of these things called osteon so come back to that in a little bit not today uh I just wanted to let you know where they are and sort of introduce them to you inside this diaphysis we also find just a small rim of spongy bone we don't find a lot just on the very inside of our compact bone and then we find a unique feature this large meary also called marrow cavity large meary or marrow cavity so it would be as I've noted before you know internally sort of running in this area here sort of tapers based on the bone size but that's where we' find our menular or marrow cavity and in long bones we can find two types of marrow red marrow or yellow marrow so I mentioned red and yellow marrow before but I think it's good to sort of revisit it now that we see where these tissues reside and what that might indicate so if we could peer inside of this diaphysis if you had a fresh bone sample and you didn't know anything about the person nothing you just were handed this fresh bone sample and you could see the marrow cavity and you discovered had a lot of red marrow what are some assumptions you could possibly make about the person from which that sample came were young they were young that's great yep maybe they were young and generally when we say young you know the next question you thinking well how young and generally the Line in the Sand that we use is puberty prepubescent preal is where we'll find a lot of red marrow post pubescent post puberty we start to transition away from red and towards yellow so there's a couple years in there where you may find sort of a a pinkish marrow and that's just sort of a marrow that's transitioning from red to Yellow so maybe they're young what else might you think about this person if we saw red marrow young as great could indicate other things though they could be an adult and have red marrow here but that's abnormal what might you think about the adult if you found red marrow here what does red marrow have a lot of why does it look red red blood cells why would an adult need a lot of red blood C cells lowess say that what lowess absolutely they spent a lot of time without adequate amounts of oxygen they needed a lot more red blood cells to satisfy that oxygen debt they had a hard time conducting oxygen or carrying oxygen so you're absolutely right so maybe they're young so that's option one or maybe they're an adult but they had some sort of um intense need intense need for extra I'm going to abbreviate rbcs specifically what are we needing oxygen we had an oxygen debt and so maybe what happened was this person was just like an extreme athlete like a professional athletic level and they were training at really high elevations we could see some conversion of their typical yellow marrow back to Red we could also see it in people that have had a major hemorrhagic event they lost a lot of blood or maybe they have COPD and they just need a lot more oxygen um or red blood cells to carry that oxygen so in an adult it either means they're a super duper athlete or they've had some sort of um blood loss or oxygen carrying problem but we can we can see it in adults it's just not typical what about yellow marrow what would you if same scenario you got a fresh bone specimen it's yellow marrow on inside what would you think about the person from which that [Applause] came abnormal or normal noral normal yeah most adults post pubescent in their large marrow cavities have yellow marrow and that's just a typical finding so if it's yellow we could maybe assume it's just a normal adult I'm using Orange for yellow cuz I don't think yellow shows up very well it's a normal adult and they were not malnourished because the yellow marrow indicates a pretty good amount of fat or adapost it has collected that's why it looks yellow it's full of yellow fat white which is more appropriately called white adapost tissue but yellow and so that's what you could assume from that so marrow gives up a lot of secrets about a person and again as I mentioned you can have um a conversion of red to yellow and that's typical that conversion of red to Yellow that's what happens during puberty you don't typically need as many red blood cells in your average adult so we're going to see that go to Yellow but you can in extreme instances have that go back and we call that a reconversion so just like any tissue this stuff is pretty malleable and um gives up a lot of Clues if you know how to ask the right questions which is the cool about Anatomy physiology you got to know the tissue but then you can start making some deductions about what happened to that person so marrow is a really cool tissue all right finishing off our bone regions here we're going to move into the metaphysis and again because this is a long bone we're going to have two metap fyces I introduce the proximal closest to the trunk and then the distal is farthest from the trunk again uh what could we say about it externally it's pretty featureless it would have periosteum on the outside as with the diaphysis I'll go ahead and bring that down because remember a bone has to be covered with something and that something is either periosteum like I'm sketching in now or articular cartilage like we would find in a joint capsule but obviously it's going to have a lot more periosteum because there's just a lot more service area associated with that periosteum and then rounding off the bottom here we have the distal farthest away from the midline or trunk epiphysis it is similar in stru structure and function to the proximal epithesis so not going to go over a lot of different things about it because it's kind of the same it's just a recapitulation this big bony knot down here sort of a fled area we will have different external features like dial medial and lateral cond dial but as far as the rest of it is concerned it's fairly similar so I'm going to go ahead and extend this periostium down and I would cover the articular area here with articular cartilage which is more appropriately called Highland cartilage articular cartilage really just describes its location it's not a very precise term as far as what type of CT is it and that type of CT te is Highland carage this nice glassy blue again a remnant of that fetal Highland carage mod model that develops way early in life and as I mentioned we have some external features here uh this would be a medial and a lateral cond making a nice articulation surface with the tibia below and then you sort of have the start to your joint capsule the knee which is an interesting joint to study all the way rounds it looks like um honestly the knee looks like a structure that was designed by a committee where everybody had to get a say in you know like if you look at the structure of a knee it just is a disaster and it's kind of an amazing thing that it lasts as well as it does sure you have problems ACL tears CCL tears but on average it lasts pretty good compared to what we ask of it couple things to finish off here make sure when you study this this is always always been a sticky point on this this particular exam people just have a hard time understanding what these are and where they are so I just like to be hyper clear with you I don't I think they make it harder than it has to be um the surface of any bone has to be covered with one of these you cannot have bare bone surface in a living body so we usually see perio again that's the orange AUM Perry means surface right above oium bone it's this membran is covering on the surface of a bone this is your osteogenic layer it has a inner layer of stem cells that can produce new bone throughout life wind stimulated it's not just going to do it for no reason that would be crazy um and then if it's not periostium it's articular carbage and we find that in areas that articulate with other bones and that is a specific type of hin cartilage so articular cartilage would be an appropriate term to use if we're talking about location if we're going to be technical though and that's kind of what this field is about is being Technical and accurate we would say it's Highland Carriage that's a type of CT that's the technical word for that Highland Carriage glassy blue resists friction helps reduce heat and reducing heat is really great at reducing in damage to that joint capsule just make sure when you're studying this you are really clear on those two things um and I think that's a good place to stop we're almost out of time and no point starting something new I'll see you on Thursday