hello and welcome let's talk today bones and skeletal tissue now here when we go through and we talk tissues and organs of the skeletal system we'll see tissues and organs of the skeletal system are going to include bones we're going to check them all out cartilage and ligaments so what we'll do first is we'll go through we'll check out skeletal cartilages get those taken care of and then we'll jump into bone get bone taken care of and then we'll jump into ligaments and get ligaments taken care of so here when we go through and we talk about skeletal cartilages we're gonna go through we'll revisit all the different cartilages that we have seen we have seen before that cartilage was the embryonic forerunner of most bones and covers as well it's going to be found covering the ends of our joint surfaces as well so it's embryonic forerunner of most bones and it covers many joint surfaces the ends of our bones where they form joint surfaces ligaments we're going to see chapter i believe nine it is or something of that nature where we'll go through check out ligaments and see a little bit more tendons we'll see ligaments are going to help hold bone to bone at a joint while tendons are going to help attach muscles to bone as we have talked about we've seen before now here when we go through and we talk about the skeleton the human skeleton as we've said before now is initially made up of cartilages and fibrous membranes but most of these are replaced then by bone the few that remain are found in regions where flexible skeletal tissue is needed so when we go through we talk about the structure of skeletal cartilage skeletal cartilage is going to be skeletal cartilage is obviously one type of cartilage tissue we've gone to we've seen we've got three different types of cartilages and we'll go through revisit all three of them and now cartilage itself is going to consist primarily of water which accounts for its resilience cartilage contains we have said before no blood vessels or nerves now skeletal cartilage is going to be surrounded by a perichondrium layer it will be surrounded by a perichondrium layer the perichondrium is a layer of dense irregular connective tissue and it contains the blood vessels from which the nutrients are going to diffuse through the matrix to reach the cartilage cells also this perichondrium it acts as a girdle to help resist outward expansion when cartilage is compressed now when we go through we talk about types of cartilage skeletal cartilage is going to contain again as i said before representatives from all three types and all have chondrocytes as we have seen lacunae right chondrocytes are found we said in the lacunae and then this is all found within an extracellular matrix the first cartilage type we had was hyaline cartilage when we talked hyaline cartilage hyaline cartilage was the most abundant skeletal cartilage it is the most abundant skeletal cartilage it's composed of so when you talk about its structure it's composed of spherical chondrocytes and fine collagen fibers which we said were not detectable microscopically the function of hyaline cartilage if you recall is to provide support with flexibility and resilience now hyland cartilage is going to be further subdivided according to the location where it's found and basically what it's doing so here we can see first we have what we call articular cartilage now articular cartilage is going to be this famous cartilage we've been talking about that's found at the ends of our bones where they form joints so covers the ends of most bones at movable joints that is going to be articular cartilage now when we talk about coastal cartilage we're talking about car or hyaline cartilage that connects the ribs to the sternum respiratory cartilage again hyaline cartilage that forms the skeleton of the larynx nasal cartilage that supports the external nose next then let's move to elastic cartilage when we talk about elastic cartilage it looks like hyaline right we looked at the structure it looks like hyland however had way more elastic fibers running through it way more stretchy elastic fibers the function we said of elastic cartilage is to stand up to repeated bending and still maintain shape it's found in the external ear we said and the epiglottis here we can appreciate the epiglottis and third we had fibro cartilage fibrocartilage we took fibrocartilage it's a highly compressible cartilage it has great tensile strength and if you recall it's basically found to have parallel rows we said of collagen fibers alternating with basically chondrocytes in lacunae so parallel rows of chondrocytes alternating with these thick collagen fibers that are found in a nice parallel arrangement now we talk fibrocartilage its function is to withstand heavy pressure and stretch to withstand heavy pressure to withstand heavy pressure and stretch the locations we said in between the vertebrae right we said these areas are going to take a lot of a shock so the intervertebral discs in between the knees and then we also mentioned in between the two hip bones here's the pubic symphysis so the neem in this guy intervertebral discs and then the pubic symphysis let's move over to bone then from skeletal cartilages let's talk bone bone is going to come in many sizes and shapes the function of bone let's talk about here as well okay along with bones the skeleton in general number one is support the skeleton provides us with the framework that supports the body for example the legs they support the rest of the torso they act as pillars protection diffused bones of the skull are going to protect the brain that's inside the vertebrae they all come together to help protect the spinal cord the ribs they're helping to protect vital organs inside the thorax movement another function right bones and tendons and muscles will all basically come together and muscles will use the bones and basically as levers and he'll basically allow parts to move mineral storage mainly calcium and phosphate and here we can also release these stored minerals into the bloodstream if we happen to be low so you can have kind of a a deposit and a withdrawal type of a system here with the minerals production of blood cells remember we call that hematopoiesis and this we said occurs in the marrow cavities of certain bones it'll happen in the narrow cavities of certain bones and then we have fat storage triglyceride storage fat is going to be stored in the bone cavities of certain bone basically certain bones and it's a source of stored energy and it's a source of stored energy acid-base balance and detoxification other functions there and detoxification now the bones of the skeleton we see we have about 207 bones at birth but some are going to fuse as we age and we have approximately 200 206 bones in us as an adult some of these bones we'll see uh are going to be accompanied by sesamoid bones which are going to be bones that are formed within tendons and they're usually formed due to stress and then also we'll have sutural bones vermin bones we're going to go through we'll look at as well and these are extra bones of the skull and they're not found in everyone not found in everyone so here let's go through and let's uh look at this classification so we've seen these 206 bones being divided up into an axial and appendicular skeleton that's basically what we're revisiting here so we talk axial skeleton we said that the axoskeleton is made up of bones that make up the skull the vertebral column and the rib cage and we talk about the function the function of the axial skeleton is protecting supporting and carrying other body parts and you can see it forms basically this uh central aspect so right inside of here in brown you can see is all axial skeleton next thing we have appendicular skeleton and we talk about the appendicular skeleton the epidermis skeleton is made up of bones of the upper and the lower limbs right upper lower appendages and also the girdles and also the girdles these are basically the bones that are going to help append the limb bones to the axial skeleton so here you've got the clavicle and then we're going to see the scapula so the limb bones plus their girdle bones here the girdle bone we've got right inside of here the hip bone the coxal bone now the function of the appendicular skeleton is locomotion to move from place to place and manipulation of the environment and manipulation of the environment these bones also get classified according to their shape they also get classified according to their shape when we classify these bones according to shape we can see we have a few different classifications here we'll check out as well first we have bones that are going to be long bones these bones are named for their elongated shape not their overall size so when we describe these bones these bones are described as being longer than they are wide and they have a shaft and two ends to them so here you could see a long bone they have a shaft and they have two ends one end and here's the other end examples of long bones all limb bones except the patella your wrist bones and your ankle bones so all limb bones except patella wrist bones and ankle bones next we have short bones short bones short bones they are going to be described as being bones that are cube shaped they're cube shaped they are equal in length and width examples of short bones will include wrist bones and ankle bones we also classify sesamoid bones here as well next then we have flat bones flat bones are thin flattened and a bit curved they are thin flattened and a bit curved examples will include the sternum our ribs our scapulae and most of our skull bones and most of our skull bones and then the fourth classification is going to be irregular bones irregular bones now when we talk about irregular bones they're described as having a complicated shape complicated shape vertebrae and your hip bones vertebrae and your hip bones examples of irregular bones let's go through let's talk about the structure of bones now we talk about we look at the structure of bones first bone is considered an organ we said in order for something to be considered an organ it's going to be made up of two or more primary tissue types so here when we go through we talk about bone being an organ bones considered an organ because it contains various tissue types number one bone tissue dominates but also bone tissue contains nerve tissue it contains nervous tissue so bone tissue is connective tissue nervous tissue right two or more primary uh tissue types we've got ourselves an organ but usually four so we'll get all four there cartilage fibrous connective tissue lining the cavities right all connective tissue has muscle muscle is going to be found over lying bone and also epithelia epithelia is going to be found in the blood vessels at service bone so you can see here all four primary tissue types now when we go through we talk about bone we're going to look at and we're going to talk about bone at three levels we'll talk about it from a gross perspective from a microscopic perspective as we have been doing and then also from a chemical perspective and also a chemical perspective now when we look at the gross anatomy of bones every bone is going to have a dense outer layer that's smooth and solid and this layer is compact bone internal to this compact bone is spongy bone if we're talking about certain bones and internal to that compact bone is going to be in other areas we'll see red bone marrow right inside the spongy bone so you got red bone marrow or you can have yellow bone marrow fat as we have mentioned so that's all going to depend on where we're at and what we're talking about we'll go through all of that we'll see all that will clarify all that too now when we go through we talk about bone having markings to it bone surface is rarely going to be uh you'll see um uh completely smooth bone surface is also going to have projections it'll display depressions it'll display openings as well and these depressions projections openings usually indicate stress from tendons ligaments and muscle and also they're going to serve as conduits so first let's talk about projections now when we go through and we talk about projections we've got all these different projections we're going to go through and all these other components we're going to go through we're going to check out we'll talk about we'll see also so here you can see we're going to have projections and there are certain projections we're going to go to we'll talk about and we'll check out but eventually you'll know basically every single one of these and what you have from here so first here we're going to go through we're going to look at tuberosities when we go through and you have to identify such and such tuberosity you have to be able to understand what you're looking for tuberosities are going to be large rounded projections they are large rounded projections and they are often they can be roughened in appearance as well for example when we're seated in the seated position we are seated on our ischial tuberosity a large rounded projection and it's rough in appearance and these can actually lead to decubitus ulcers in patients who are in a seated position for prolonged periods of time it's a pressure point next thing we have tubercles so if you hear tubercles what you have there is you have small rounded projection or a process a small rounded projection or a process a crest when you hear of a crest a crest is going to be a narrow ridge of bone and it's usually prominent you could feel it here we can see on this hip bone we've got the iliac crest it's an important landmark we're going to use you also use the term line a line is going to be a narrow ridge of bone it's less prominent than a crest narrow ridge of bone and it's less prominent than a crest here you can see the intertrochanteric line and that is the term epicondyle the prefix epi tells you this is something that's going to be found uh basically on or above so epicondyle is a raised area on or above a condyle epicondyle a raised area on or above a condyle so here we can appreciate the medial epicondyle right out here is going to be the lateral epicondyle and these are the actual condyles we're going to see these huge projections that serve as basically the term there's articulating sites next one we have the term trochanter here the two trochanters you have to know about and trochanters are very large blunt irregularly shaped processes very large blunt irregularly shaped processes and these are the only two you have to know about is going to be the ones on the femur so these are projections again they're outward growths bulges you can think of from the bones surface and these specifically speaking the ones we just went over are going to be projections that attach to muscles projections that attach to muscles next in here we have projections that are going to help form joints before we jump to there we forgot two of them we have spine and process spine is going to be a sharp slender often pointed projection right inside of here we can see an ischial spine here this looks this is a sharp pointed process a spinous process so you see you can apply that term and then we use the term process processes any bony prominence basically any bony prominence kind of like a generic term i guess you could say it's a process any bony prominence next in here we can see we've got projections that are going to help form joints now we talk about projections that are going to help form joints here we have a few of them we have four of them that i want you to know about first term is a head when you hear the term head the head is going to be a bony expansion it's a bony expansion that's carried on a narrow neck so right here we have our rib right here on the rib you can appreciate the head of the rib here then is the neck basically the constricted part so you can see that bony expansion carried on a narrow neck next is a condyle when we use the term condyle we're talking about you can see a rounded articular projection we are talking about a rounded articular projection here we saw we're gonna have a condyle here the lateral condyle of the femur and the medial condyle of the femur they're better appreciated on the back next then we've got after the condyle we've got a ramus remus is the arm-like bar of the bone here you can see it's the arm-like bar of a bone and then last we have facet facet when we talk facet facet is a smooth or nearly flat articular surface so right here you can see a smooth nearly flat articular surface next let's check out some depressions and we'll look at some openings as well now depressions and openings we'll see are going to allow for the passage of especially the openings for uh nerves and blood vessels and we talked depressions they'll actually contain certain org certain structures so first we have fosse fosei are going to be shallow basin-like depressions in a bone here in the skull we're going to be able to appreciate the anterior cranial fossa middle cranial fossa and we're gonna have a posterior cranial fossa it's gonna contain the actual brain different parts of the brain so shallow basin-like depressions in a bone whenever you hear anterior cranial fossa that's again you have to be able to recall all of these terms from this chapter next is the term groove groove groove is a furrow it's a furrow a passage again for blood vessels next then is going to be a meatus a meatus is a canal like passageway it's a canal like passageway here are external acoustic meatus sound travels through to hit the tympanic membrane next is fissure fissure is a narrow slit like opening a narrow slit like opening and then we have the term foramin foramen is going to be a round or an oval opening through a bone a round or oval opening through a bone nexon is the term notch notch is an indentation at the edge of a structure it's an indentation at the edge of a structure here we can appreciate a nice notch right inside of here right inside here next we have the term sinus when we talk sinus sinus is basically a cavity within a bone it's where the inside of the bone has been riddled out and it's lined with mucous membrane and filled with air so cavity within a bone next then we have bone textures so here we can go through we can see we have compact bone and spongy bone and then we have yellow bone marrow as well we'll go through we'll look at so we talk uh bone textures compact bone spongy bone every bone we said is going to have an outer dense layer and compact bone you can to the naked eye and an inner spongy bone layer now compact bone is the external layer while spongy bone is internal to the compact bone and spongy bone is a honeycomb of small needle like or flat pieces called trabeculae and these trabeculae in spongy bone basically they're tiny bone struts they're tiny bone struts and these tiny bone struts are going to help bone resist stress they will help bone resist stress let's actually go through and let's look at the structure of a long bone so here we can see long bone structure and we talk about long bone structure long bones will have a diaphysis a shaft to them as we can see here they will have a shaft to them a diaphysis and the shaft forms the long axis of the bone the diaphysis is constructed of a thick basically it's constructed of thick layers of compact bone that surrounds a central medullary cavity that surrounds a central medullary cavity the medullary cavity is yellow marrow cavity it's called the yellow marrow cavity and it contains fat we're talking adults it'll contain fat then we also have the epiphyses so here you can see all that fat the yellow marrow cavity next then we have the epiphyses the bone ends the epiphyses the bone ends are formed of compact bone and spongy bone the joint surface as we talked about is covered by a thin layer of articular or hyaline cartilage now internal to the compact bone in the epiphyses we have what we call metabolic tissue red bone marrow hematopoietic tissue now this hematopoietic tissue red bone marrow is found within the trabecular cavities of spongy bone and also in the diplo of flat bones in the center of flat bones this hematopoietic tissue is more active in these flat bones because they have less fat containing medullary cavity like long bones do so we'll resort to those bones if we need to take basically a sample of hematopoietic tissue here we can also appreciate the epiphyseal line the epiphyseal line is also known as the metaphysis also known as the metaphysis it's found in adults and it's located between the diaphysis and the epiphyses located between the diaphysis and the epiphyses and what it is is it's a remnant it's a remnant of the epiphyseal plate next then is the epiphyseal plate the epiphyseal plate is found in basically children all the way up to where growth is going to basically end the epiphyseal plate is a disc of hyaline cartilage that grows during childhood to lengthen bone next thing we have membranes or coverings the first covering i'd like to talk to you about here is the periosteum the periosteum is a glistening white double layered membrane it's a glistening white double layered membrane that covers the entire external surface of long bones except for the joint surfaces because there we have hyaline cartilage so here we can appreciate long bone here we've got the periosteum peeled back this periosteum has got two layers so first layer is the fibrous layer the fibrous layer is the outer layer it's an outer layer of dense irregular connective tissue the second layer is the osteogenic layer that's the inner layer the osteogenic layer the inner layer it consists of osteoblasts bone germinators and then we have perforating fibers or sharpays fibers these perforating fibers or sharpays fibers they you can see here are going to help secure the periosteum to the bone they will help secure the periosteum to the bone what they are they're tuffs of collagen they are tufts of collagen which extend from the fibrous layer of that periosteum to the bone matrix all the way to the bone matrix also appreciated here nutrient foramina the nutrient foramina you can see here are going to be tiny openings openings in the periosteum and what they do is they supply nerve fibers blood vessels lymphatic vessels as we see here to the diaphysis of the bone and then we can see here end osteom when we talk end ostium now endosteum is delicate connective tissue it's a delicate connective tissue membrane that covers the internal bone surface that covers the internal bone surface and osteum it covers the trabeculae of spongy bone and lines the canals so that is the structure of our long bones next then let's move to short flat and irregular bones and their structure when we talk short flat and irregular bones and their structure i want you to know they have no shaft they have no epiphyses they do not have any type of a shaft nor epiphyses they do have very active marrows they have active merrell soul that marrow is going to be used for biopsies so for example we'll go to the sternum or even the hip bones the coxal bones and here you could see basically looks like a sandwich they refer to it as a diplo where you have a layer of compact bone compact bone and then the center spongy bone and we zoom in on the spongy bone here you can appreciate the trabeculae tiny bone struts next let's look at the microscopic anatomy of bones when we talk microscopic anatomy of bones we're going to be looking at then basically bone cells we talk bone cells osteoblast osteocytes and osteoclasts and we've talked about what each of them do osteoblasts bone-forming cells osteocytes are the mature bone cells they're found in the lacunae and they use those kind of liculide to basically pass receive nutrients and so forth and then you have osteoclasts third type bone dissolving cells they'll break down bone bone dissolving macrophages and we also have osteogenic cells stem cells osteoporo progenitor cells so here when we go through we talk about now uh compact bone compact bone looks dense but contains passageways for nerves and vessels compact bone i want you to know is it is adapted to support weight and withstand tension stress so here when we look at compact bone under the microscope here we can appreciate one osteon and the one osteon has been broken down into you can see a whole bunch of lamellae and then the central canals we've talked about so let's move from here to here here you can appreciate the same thing same thing here same thing here so we'll remove one osteon and here you can appreciate all the various lamellae so we go through we talk osteons osteons are known as the haversian system aversion system what they are they're the structural units of compact bone they are the structural units of compact bone now here in relation to these osteons we can appreciate the lamellae so like we said before the lamellae are like little plates they're hollow tubes you can think of hollow tubes of bone matrix found surrounding the central canal found surrounding the central canal the central canal then also known as the haversian canal it runs through the core of each osteon and it's going to contain as you can see blood vessels and nerve fibers then we have our perforating or volkman's canals these perforating or volkman's canals we said are found lying at right angles to the long axis of the bone and what they do is they connect the blood and the nerve supply of the periosteum to those in the central canals and the medullary cavity also appreciated here the lacunae the little hollow spaces found at the junctions of the lamellae and we have said they are occupied by osteocytes here you can see the little osteocytes are very nicely right inside of there then you have your canaliculi so cantaliculi we described as being uh in the lab you'll see there as well here we can see they're going to be described as being little hair-like canals which connect lacunae to each other and to the central canal which connect lacunae to each other and then to the central canal now we talk lamellae we have two types of lamellae so let's move out to here and here we can appreciate the two types of lamellae we have first what we call interstitial lamellae interstitial lamellae now interstitial lamellae are going to be the lamellae that fill the gaps in between the osteons so that's what we've been looking at are basically these interstitial lamellae and you also have your circumferential lamellae the circumferential lamellae you can see right outside of here these are deep to the peri deep to the periosteum so right here's the periosteum just deep to the periosteum and they're going to be superficial to the endosteum and they're spanning the entire diaphysis they resist long bone twisting they resist long bone twisting next then we have spongy bone so when we talk spongy bone spongy bone we've gone through we've talked about we've seen everything in relation to spongy bone so make sure you review that and you've got everything down in relation to spongy bone let's talk then the chemical composition of bone so let's look at bone from a chemical perspective now there's a balance of two let's talk about the chemical composition of bones when we talk about the chemical composition of bones we're going to see we have a balance of two major components that's going to keep bone strong and durable and that composition of the two main components is going to be we'll see organic components and inorganic components when we talk about the organic components the organic components will include cells and the cells we've seen all three types and we also have osteoid osteoid is the organic part of the matrix and this includes the ground substance and the collagen fibers then the inorganic components will include the hydroxyapatites mostly which are your mineral salts largely calcium phosphates and then ten percent calcium carbonate and the other five percent is going to be inorganic minerals so here we could see a patient with normal height and here we have a patient with dwarfism dwarfism and we'll talk more about that when we get to endocrine