all right so let's uh do the skeletal system um the way i broke up the skeletal system is there's the lab section and then there's a lecture section the lab section which we'll do later on during the course is the actual names of the bones the humors and it's seven parts the femur and it's 20 parts it's the skull and it's 50 parts whatever something to look forward to but the lecture portion is about classifying the muscle or the classifying the bones how bones form in the fetus how after let's say a fracture occurs how does it fuse together we'll talk about articulations it's more of the fear the physiology although we'll be talking a little bit about anatomy and some of it as i mentioned before is the lecture is also going to pertain a little bit of histology of bone also so there's going to be an overlap of what i talked about last time in uh histology okay so uh let's get started with the skeletal system this is how you're all feeling after that wonderful exam i realized that okay okay so the skeletal system we have vanishing bones sometime in your life you're going to lose 600 bones before your bone you had over 800 bones separate bones but many fused and you were born with about 450 bones and then you have more fusion going on of these bones throughout your childhood and adolescents life and when you reach about age 20 you have the full set of adults a full set of adult bones and a skeleton of 206 bones okay but you lose a lot okay so we call it banishing bones where this all comes about we're going to get into okay now skeletal system deals with bones right it consists with bones but it also is going to deal with cartilage tendons and ligaments remember what i said ligaments connect bones to bones tendons connect connect muscles to bones like tend to think of muscles being very tense right tendons right okay functions of the skeletal system it's going to support soft organs fight against gravity and keeps us upstream it's going to protect soft organs you've got a skull to protect the brain you've got a rib cage to protect the heart and lungs you've got a vertebral column to protect a very vital spinal cord so it's going to protect soft organs here it's also going to provide movement muscles will be attached here and you can actually move from one place to another it'll store calcium and other salts not just calcium sure calcium is the big one along with phosphate you need a lot of phosphate when we have to deal with atp right but sodium's in there and potassium magnesium a bunch of other inorganic stuff it's going to store fat in what we call the yellow bone marrow the red and yellow bone marrow we'll talk about that later we're also going to have hematopoiesis as i mentioned before blood cell formation that'll be located in the red bone marrow okay so let's see how we're going to classify bones we could have long bones they're going to be longer than wider these are mainly bones of your four limbs including your fingers including your toes the only thing it doesn't include is your wrist bones your ankle bones your knee bones okay short bones they're going to be as they said little stubby things cubes these will be located in your wrist and your ankles they're known as the carpals and the tarsals i think after the first exam this should start ringing bells and you can see why you need to know that chapter one stuff because it's gonna make your life easier later on we also have flat bones the flat bones like your shoulder the shoulder blade is flat believe it or not your bones and your skull are flat they're curved but they're flat when you look at it the sternum which is your chest plate is flat too the ribs you would think that well they're round well not necessarily there's a rib and if we take a cross section of it it's not like this it's more like this flattened and when you get into the bones and lab you'll feel them see that they are flattened they're then there's bones that are just they don't fit any category we call them irregular bones it's kind of sad to be an irregular bone okay now your vertebrae all the bones in your backbone they don't fit in category like that and you'll learn about those there are two bones in the skull that are not flat one looks like a bat it's called the sphenoid bone that doesn't fit in any category as well as another one that kind of looks more cube-like than anything but it's got other points to it that's called the ethmoid mole and you'll see those later on so these are the different types here's the long bones over here short bones these are flat bones and these just don't have a place for them just sad to be an irregular bone okay all right let's look at features of a long bone though it's much easier to talk about the features of a long bone as opposed to these other bones but it's not bad what i'm going to do first is define the define the parts of the long bone and then i'll uh well as i do that i'll be drawing pictures and then i'll show you the actual diagrams on the next few slides the diaphysis that's the actual shaft of the bone so we're going to take a bone like this um actually people are like oh i just started drilling now you just keep it there all right i'm going to just make it a little bit shorter but i'm going to do some other stuff with this so the diaphysis is going to be this area right here the shaft of the bone okay we also have the epiphysis that's going to be the ends of the bone and because you took the first exam you know that long bones must have a proximal epiphysis and a distal so efficiency gotta put it all together right at the ends of these bones there's going to be what we call articular cartilage that's going to be made up of hyaline cartilage if we have another bone over here that it's going to articulate with this bone will also have articular cartilage cartilage does not have any nerves in it cartilage doesn't have any blood vessels in here bone has both so what this is let's say your femur and your tibia your thigh bone and your shin bone the weight on here you're not going to feel so much pressure because it's riding right on top of the cartilage so the cartilages have nerve nerves it's not going to hurt all that pressure but as you use your knees over the decades this cartilage is going to start grinding down on itself and what's going to happen here is that you're going to have exposed bone there now you're going to have bone to bone on certain areas you'll be feeling the pain for that this is called osteoarthritis okay and what will happen is you'll see that as this grinds on each other it'll start wearing down on the bone and then the bone tries to adapt and make more bone but it has no place to go because you've got to let it sit there for six to eight weeks we're going to get into that for fractures so it has no place to go so the bone starts growing in weird places these are called osteophytes and you'll see that in a few slides later on these are called osteophytes or better known to laymen as spurs now it's not smooth anymore so you're not going to be able to it's more rocky you're not going to be able to bend your joint as much as what you have before your range of motion has been limited and if you know people have osteoarthritis that's what they're complaining of the pain and that they can't bend their hands as much as we did before so the articular cartilage is a protective thing to allow us to run and jog and do all the normal activities that we can be kind to your knees please okay you can't grow back your cartilage there's no really blood vessels there once it's gone it's gone now back to the diaphysis in the center here there's going to be a medullary cavity as i explained to you in histology in children it's red bone marrow and that's where all the blood cells are being made in adults it's yellow bone marrow and that's where fat is being stored amongst other places we do have red bone marrow and adults but not in the long bones they're in the skull invertebrate now we have something called an epiphyseal plate the epiphyseal plate is located in between the diaphysis and the epiphysis in this area right here right here this is the part where we're going to have the lung bone grow lengthwise there's hyaline cartilage in these epiphyseal plates and we have something called the transition zone if i draw it like this the epiphyseal plate is here there's hyaline cartilage here it goes through mitosis this cell over here will go through mitosis to make two cells going up and well one will stay there does that make sense this one and then this one will have one that goes this way and one to move up this one you see how it's growing lengthwise over the years this is what we call the epiphyseal plate at about 20 21 years old the hyaline cartilage doesn't do that anymore it stops going through mitosis we say that the epiphyseal plate fuses and when it fuses you don't have growth anymore this mitosis happens much faster during puberty and thus you get the name or the term the growth rate increases right the growth spurt you're always growing you're like here it's like eight years old nine years old 10 years old 11 12 13 14 15 and then it goes like that right you see i mean it just goes faster when it fuses we learn we now call it something called the epiphyseal line when we get into fractures you can start seeing things having problems if you have a fracture of your bone and it goes in and the fracture goes into the epiphyseal plate and you're only five years old do you see what's going to happen here how one bone is going to grow faster than the other one those are murderous to actually fix when i say murderous it is very painful and i'll explain that towards the end of the skeletal system they have to crank on this thing and stretch it every day the metaphysis is where the epiphyseal plate is located so you have the diaphysis piphasis and the metaphysis is actually here it contains the epiphyseal plate the periosteum it's that tough fibrous connective tissue that's going around on the outside keeping the bone together and i showed you that with that model i also mentioned to you that if you go to kfc you get your bone after you eat all the meat and you start picking at the bone and starting to let it fray a little bit off the side of the bone that's periosteum okay the periosteum covers everywhere on the bone except where the articular cartilage is the periosteum will also have little holes in it a hole is referred to as a foramina you'll see that word popping up quite often we get into bone bones and lab it's called a nutrient foramina it's going to allow the blood vessels coming from outside going in to the bone itself the endosteum is going to line the medullary cavity and that'll contain osteoclasts chewing away at the bone and putting it into the calcium into the bloodstream okay so proximal emphasis distal epiphysis there's your diaphysis you see the mendulari cavity in this case yellow bone marrow you also see periosteum around here but let's take this big chunk here and zoom it up sorry man okay here's the periosteum you could also see the nutrient foramina where the blood vessels are going to go through those holes there's the yellow bone marrow and as i showed you in histology you can also see some of the compact bone the endosteum which is not oh it is labeled there is the lining of the medullary cavity where the yellow bone marrow is in this picture bone marrow red bone marrows in children and adults obviously adults have it too you're still making red blood cells this is where the site of hematopoiesis where blood formation takes place in adults we have yellow bone marrow though and that's going to store triglycerides and energy right it's all your fat now from out of polices where does it take place in the embryo and fetus it takes place in the liver and in the spleen and even before that like the first two weeks of gestation after fertilization it actually occurs in the yolk sac but we lose the yolk sac pretty uh pretty early in the embryo in the embryo but then we go into liver and spleen that makes the red blood cells and white blood cells and platelets in children the red bone marrow is mainly in the well it's in the long bones mainly in the legs typically the femur and the tibia femur is the thigh bone and tibia is the uh chin bone in adults the red bone marrow its primary source is going to be the trunk and the head so the chest plate the ribs the skull the vertebrae that's where the main place is but let's say you're losing a lot of blood maybe god forbid you have cancer and your body is as soon as it's making a red blood cell it's going away because the cancer is just taking it all away or you have leukemia and it's it's not making enough white blood cells that are functioning so then the bone marrow in an adult let's say a 40 year old the bone marrow says look we need to make more red blood cells we need to make more blood cells so it goes up to the brain and says hey brain you know we're in the skull right now and you're our buddy right inside of here but your body has these conversations okay and it says look we used to make blood over in the legs when we were a child the factories are still there is it possible that we can actually turn them back on because we need to make more red blood cells the brain says that's a wonderful idea they have this conversation and what happens here is that the bones in or the other bloke the um the marrow in the legs starts kicking on an adult it's more active during that time and when it does because it's more active these people tend to get leg pain because it's not usually something that the legs are doing in adulthood okay if they need more red blood cells than what the legs are doing then it says well we really did it when we were an embryo in our mother's womb god rest her soul but we used to make it in the liver and spleen factories are still there and then that would kick on over there okay now i don't want people to think but i have leg pain does that mean no that doesn't you got to put everything together that doesn't mean you have cancer i'm just saying if one has cancer it would make sense why their leg why they would have leg pain okay god i want everyone to have a basket become get a complex here okay but does that make sense about primary secondary tertiary sources okay and in the adult all the red area skeleton is where the primary source is okay all right now bone structure and bone histology for the most part this is going to be review for you for histology this is where it's kind of bridging together for that first that second exam for you the bone structure as many as muos made up of many tissues it's not just hard stuff all right there's cartilage or connective tissue in there there's cartilage in there there's vascular tissue lymphatics adipose tissue nervous tissue there's other things in there than that hard bony stuff it's mostly bony hard stuff but there is other stuff in there now we look at this we got two forms of bone in your bone there's compact bone which is going to be a solid thing and those are where those tree stumps were if you're looking at a microscope but then you've got the spongy bone that's over here also the spongy bone is that loofah i was telling you about that you ladies have in that in the bathtub okay you know what i'm talking about so we have you could also call cancer stone trabecular bone it's all the same stuff okay all those interwoven stuff those little spongy areas those lines going through there have a special name they call it trabeculae okay the spongy bone is going to be surrounding it'll be underneath or deep to the to the end right it's going to have the medullary cavity which has the bone marrow and then the lining of that is going to be endosteum and then i guess outside of that is going to be spongy bone and then compact bone okay so you'll see spongy bone kind of underlying the endosteum here but it's going to all be in the ends of the bones also the epiphyses you're not going to find any compact bone in the epiphyses and we'll explain that later on when we talk about ossification so if you take a cross-section of the bone itself and i kind of drew that for you yesterday there's the bone marrow which is in the medullary cavity the lining of the medullary cavity is going to be endosteum then you've got spongy bone here compact bone and then this thin layer out here is the periosteum okay questions on that okay so you saw this before this is what it looks like histologically we'll show that a little bit better later on but they look like tree stumps cut tree stumps and those concentric rings that you see the bulls eyes so to say is what we call lamellae yeah the other thing i forgot to mention but the center bullseye over here is called the haversian canal okay where we have perversion blood vessels there's a couple other names they could call it too osteonic canals and central canal all right a lot of different names for the same thing running the theme in amp okay here's what spongy bone looks like histologically which you won't have to worry about in histology but here you have the bone trabeculae and then in between here you're going to find fat tissue adipose tissue okay now specialized cells of the bone which we mentioned before not the first one though something called osteoporogenator cells these are basically the stem cells these osteoporosis cells are going to make all these cells here it's our stem cell and two percent of bone consists of these living cells so your bone is not just hard it's living too okay so the osteoporogenator cells will make the osteoblasts and then indirectly the osteoblasts will become osteocytes once they go into a lacuna so directly it makes an osteoblast indirectly makes an osteocyte does that make sense if you don't have the osteoblast you can't have the osteocyte they also will make the osteoclasts the little pac-man that we talked about even before the osteoporogenator cell was ever developed it came from another thing called mesenchyme mesenchyme is a very high and a very undifferentiated cell stem cell that makes all the connective tissue it makes the blood cells it makes the uh the cartilage cells it makes the fibroblasts for the connective tissue proper it makes the osteoprogenator cells also so these are the bone stem cells undivided cells that will turn into osteoclasts or osteoblasts and then indirectly the osteoblast becomes the osteocyte okay osteoblasts as i mentioned to you before if i wanted to paint this floor over here i'm going to get someone who could just put down the bulk of paint on the floor all right doesn't mess it'll be messy it's just going to take the paint and it's going to put it all over the floor i'm going to paint the whole floor no big thing paint it all over and then they can't paint themselves or paint anymore because they paint themselves in a little corner and i can't go anywhere now they have this little hole they live in called the lacuna and now they're known as an osteocyte meanwhile that paint or calcium needs to go into the bloodstream at certain times from muscle contraction for nerve stimulation for whichever so the osteoclasts are going to come in here osteoclasts are going to chomp away and put the calcium back into the blood but the osteoblast is going to lay down the bulk of the bone this is called osteoid okay osteoid is bone matrix without the organic substance that gets laid down later the organic substance we're talking about is collagen that's in there the inorganic minerals magnesium calcium and stuff is added much later there's something called hydroxyapatite hydroxyapatite is actually the hard stuff the cement of the bone hydroxyapatite is made up of calcium and phosphate crystals and that's the bulk of the bone itself osteocytes as i said before they were once osteoblasts that painted themselves on a little corner and now they have no place to go now they're going to be able to get all the nutrients from the aversion canals that contain the herbergian blood vessels and pass those nutrients from one osteocyte to another in the lacuna by way of those little rivers called canaliculi and it will pass those nutrients throughout the rest of the bone so the osteoblasts are our builders okay they're going to put calcium into the bone then we have osteoclasts like little pac-man they're giant multinucleated cells that have a lot of lysosomes in it lysosomes are going to digest things so it's going to digest the bone to put it into the bloodstream at least the calcium into the bloodstream when it does that we say that it resorbs bone little fancy word okay and it shapes the bone we're gonna see also if this is gonna be your bone over here and you break the bone osteoclass i'm sorry osteoblasts are going to fill this all in with calcium like glue and if we leave it like that the bone is not going to look right it'll have a bump over here and have a bump over here so osteoclasts class are going to shape the bone little pac-man it's gonna chew away at this and put it into the bloodstream so that this little bump here is not so noticeable but you don't break bones all the time so obviously class do other things more important just to put the calcium into the bloodstream so we can use it for other things as i said nerve conduction muscle contraction so it's going to release the calcium into the bloodstream so if we increase osteoclast activity calcium will go up in the blood if we decrease osteoclast activity we're going to decrease the calcium in the blood okay pretty straightforward if the osteoclast activity is too excessive your bones become brittle does that make sense estrogen when someone has a lot of estrogen just during your child bearing age and a woman the estrogen keeps the osteoclasts toned down don't get too active it's like a parental thing all right we like you over there you're doing your job just don't get too active when they go through menopause at 50 51 years old the estrogen goes down and the osteoclast activity becomes excessive what's that disease that they're more prone to getting osteoporosis and that can lead to fractures okay so osteoclasts are the sculptures osteoblasts put the clay on here just put piles of clay on here bulk it up osteoclasts is going to chisel away and turn into a michelangelo okay if you think of that one so when you compare it throughout your entire life now look at the legend over here because i don't want to get mixed up ob is osteoblast oc is osteoclast not osteocyte okay in a child you have more osteoblast activity than you do osteoclast activity you're building bone as an adult it should be about equal when we get older even us guys when we're like seven years old or so the osteoblasts activity is a lot less than the osteoclasts and the osteoclasts become excessive and that's why we see osteoporosis and much later in life so this is what your bone is made out of and i'm not going to ask you about the percentages i want you to see the the concept here that a third of your bone is organic mostly collagen so you have this organic stuff in it it's not just cement the biggest part though is here which is calcium and also here which is phosphate when you put calcium and phosphate together it's called hydroxyapatite which makes up more than 50 percent of bone there's other stuff in there like magnesium and sodium and carbonate and so forth but these are the big ones okay so why do we have collagen in there well this is the way bone is you have collagen which is organic stuff you have hard stuff which is going to be hydroxyapatite calcium minerals and then you've got the collagen in here if we remove the mineral remove the calcium then what's left in there is collagen right collagen is going to be able to bend and you can do am i doing a sales picture saying so much all right tell you what i'm thinking about right if you take your phone from kfc or wherever and you put it in vinegar acetic acid the acetic acid will actually combine with the react with the calcium and pull the calcium out of the bone you leave it in there in a bowl of acetic acid vinegar just regular vinegar for about two to three days take the bone out keep it submerged make sure because sometimes it floats so put a spoon on or whatever keep it submerged and then take it out about two or three days you'll be able to do this bend it all the way around you'll see a lot of foam on top the acetic acid precipitates with the uh with the calcium so that's what that foam is on there but it's safe to do even for kids okay so that's what happens you can also do that with an egg right there's calcium on the hard shell you put that egg in vinegar acetic acid keep it because it'll float so keep it submerged in the vinegar about two to three days take it out and you know when you crack open an egg the shell breaks of course but then you got that film that happens underneath it's called corian okay that'll stay intact but all that calcium came off and you've got what we call a rubber egg it's not really rubber it's that corion that's underneath and that's what happens there so that's what happens if we remove the collagen yes we remove no i'm sorry if we remove the calcium if we remove the collagen then your bones are like glass it shatters so you need the two it's going to give it sturdiness but it's going to give a little bit it's basically if you take a glass bowl over here and drop it on the floor it's going to shatter but you take a plastic bowl over here and make it fall it won't you see and it gives it some flexibility but yet it's still firm so does that make sense does that tell you the significance why we have the two in there all right let's talk about diseases then because what if is there a disease where the minerals is removed is there a disease where the collagen is removed yes rickets who here's heard of rickets okay we don't see it as much because we're in third world countries yes but first of all countries no because we have a good balanced diet in you know uh in the schools and stuff but it's soft bones due to calcium salts that are decreased in the body so they either have a lack of calcium in a diet in their diet or vitamin d which is needed for calcium absorption in your diet it's common it's a common disease in a third world country in children in adults it does but what adults don't have rickets they call it something else they call it a neater word it's called osteomalacia which means bone softening okay and that's for people who have like you know adults who have a decrease in calcium in their diet so what happens with them in toddlers and older children how the weight is distributed it's either their their legs start bending like you saw with the bone with the chicken bone right so what happens is the bones in their legs they'll either become knock knees or they're going to be bold lit because of all that weight it starts bending the bones because it can't hold it up straight they'll get bone pain dental problems too because your teeth are sorry your jaw is holding your teeth but they soften the jaws soften so the teeth start coming out the holes get bigger because they just mold to that and it's soft the muscle weakness hypocase calcimia hypocalcemia is a decrease of calcium in the blood for that obvious reason okay no minimum muscle weakness because like i said calcium is needed for muscle contraction you'll learn about that later all right fractures you get especially something called green stick fat fractures which we'll talk about when we get into fractures so here's where you got knock knees going on here and by the way i'm not going to ask you to tell me these names over here don't worry about that i just want you to understand what you would get with something if you have ricketts and why you have knock knees over here or both legs over here okay now what happens if we remove the collagen so that your bones become glass that's called osteogenesis imperfecta so you get brittle bones due to a decrease in collagen in the bones sometimes called brittle bone disease it's a genetic disorder that makes defective or just no collagen now there's eight different types you don't have to worry about just understand the concept of the disease when you have no minerals in there i'm sorry no collagen in there okay collagen is all over your body it's not just in the bones so other things are affected and one thing that we classically see in people with osteogenic imperfecta is that there's sclera the whites in their eyes are grayish in color because there's collagen that's in there too right connective tissue that'll be in there so that gets distorted and it creates this this grayish color that's why i look at people i know you have i know what you have i know i just help and because i know all these things to look for it's just not that i want to it's just the way we're trained and you will too when you get into a medical field you just tend to look at people and say i want to go up there and say i know you got but i do do that i mean you know i've had people come up with students actually about three years ago someone one of the students came up and said can you guess what i have i said you know this is you know because not that i encourage that but i'm you know they said they don't want to challenge me that's fine um i you know i was looking and said i don't know you know but i looked at his eyes and they're like a grayish color so i said how many bones have you broken in your in your in your lifetime because you know what i have because i went right to the question you know what i'm saying um but yet they have a lot of fractures loose joints dental problems poor muscle tone hearing loss we've got bones in here too that get affected okay respiratory problems because the lungs don't develop properly again collagen is found everywhere there's a movie with samuel jackson yeah and um bruce willis right yeah unbreakable yeah and it was this guy that broke all his bones he had osteogenic and perfected his he had glass bones yeah mr gla yeah something like that he was a superhero and it was actually a pretty good movie i don't know why he didn't do so well but um watch it after this course is over all right but anyway that's what that is and you see this i don't know if you can see the lights but you have this gray sclera there now don't get me wrong some people are just born with greatness in the in this clear i don't want people to say oh i know what you got what do you mean i haven't braided all my life you know so um but if they're breaking bones if they have let's say you know two fractures a year and they have this you know i'm putting things together here that's something to catch on early instead of catching on when you're 20 years old to see what you have right so that's osteogenic imperfecta and this kid has it too if you actually not that you would i don't think anyone here look you know i would say stalking him but i mean looked up wikipedia and stuff he has osteogenic and perfect you can see how many fractures he's had in his lifetime he's had numerous okay i guess if you get really close up to his eyes you'll see the slayer of this like grayish and color right he's using that what's that show the uh middle malcolm in the middle something like that yeah or something like that right all right so anyway that's osteogenic uh osteogenesis is imperfected a lot all right now bone growth regulation it's stimulated by hormones okay we have growth hormone that comes from our pituitary gland so we've got to make sure that pituitary gland is functioning well otherwise it's going to affect the growth sex hormones testosterone and estrogen as you know in puberty that's going to affect the growth spurt also thyroid hormones if someone has something wrong with the thyroid at a young age it's going to affect the growth these are all hormones that are doing this now calcium control the body can't make its own calcium so we always have to have a good supply of calcium coming in but it's a lot stored in the bone but we can't just use the bone and it goes away it goes out your pee and whatnot so you always got to replenish it so this too is hormonally controlled this a hormone called the parathyroid hormone don't get mixed up with the thyroid hormone they're two totally different things the only reason why it's called a parathyroid hormone is because the prefix para means next to so these are little p like structures glands that are located next to the thyroid they're called a parathyroid gland and they secrete parathyroid hormone parathyroid hormone or pth gets released when calcium levels in the blood are low then the parathyroid hormone is going to get released and target a few places so this hormone is going to target the bone and say mr osteoclast do your thing to get the calcium in the blood so they increase osteoclast activity they will also target the intestines to say hey look you're eating a lot of food and i know there's food in there that has calcium well don't make any of it go out your poop we need to absorb quite a bit more than what we usually need it'll also target your kidneys the kidneys are going to excrete excessive calcium but the pth is going to say don't let that calcium escape the kidneys reabsorb it back into your bloodstream so the pth purifier hormone targets osteoclasts in the bone intestines and also the kidneys that put everything try and get the calcium back into the bloodstream then we have calcitonin calcitonin is a hormone that comes from the thyroid gland and when calcium levels are very high in the blood calcitonin comes out of the thyroid and tells the bone to say take that calcium in the blood and mr osteoblasts put it back into the bone so calcitonin is going to tone down calcium hey there's a nice mnemonic right parathyroid gland a parathyroid hormone is going to increase calcium in the blood calcitonin is going to decrease calcium in the blood does that make sense okay and like i just said these are targeted organs they go to bone kidney intestines and these are the things that it does that i just explained to you okay pth does this in the bone does this the intestines does this in the kidney this is stuff i just explained but there it is in words calcitonin goes to the same spots but do the opposite effect skin skin is also important in terms of calcium regulation specifically vitamin d vitamin d synthesis is going to part of it's going to be needed in the synthesis process by the skin ultraviolet light from the sun is going to stimulate the skin to start making vitamin d you only need about 45 minutes of sunlight each week for this to occur i go to my doctor in february you want to do a vitamin d level on i say don't do it first off it's three hundred dollars secondly i know it's low i'm not wearing tank tops in february does that make sense all right so you expect it to be low all right so you just know in the winter months you should be taking more calcium in the winter months not in florida but up here you see i mean all right so it makes sense the vitamin d is needed to help absorb calcium in your diet so it's going to target the intestines to make sure we can really absorb things from the calcium from our diet the kidneys are going to also help control calcium they're going to make something called trial calcitriol is basically well physiologically it's the same thing as pth it works the same way it's just not coming from the parathyroid gland but it works the same way it's the most active form of vitamin d it's also found in fortified milk and it's activated by the kidney the skin and liver as i showed you skin is needed for vitamin d synthesis also so the skin the liver and the kidney are all working together to make this active form of vitamin d called calcitriol which is going to help increase calcium into the bloodstream just the way pth would parathyroid learning work okay if you have something called hypercalcemia that's an increase of calcium in the bloodstream and this is going to have side effects you have too much calcium in your bloodstream the kidneys are going to be overwhelmed with all this calcium and it's going to get started getting clogged with calcium and forming calcium stones so you're going to have kidney stones you'll have brittle bones because the osteoclasts are working overtime you'll have confusion you're going to need calcium needed for one neuron going to another neuron you'll have stomach ulcers and muscle weakness so my little mnemonic on this is stones bones moans and groans right stones and bones you know groans he's like ah moans like all right hypocalcemia a decrease of calcium in the blood and that's going to affect uh nerve transmission you'll understand how calcium works when we get there which will get tingling sensation muscle spasms we'll get into those later all right so compact bone you got the virgin system we saw in histology it's also known as an osteon it's the functional unit of of a compact bone those cylinders that we saw and i'll show you pictures of that the virgin canal is in the center of each one of those virgin systems it's the bullseye so to say it's also known as a central canal it's also known as an osteonic canal they're the ones that go the length of the bone but then we also have canals that make like h's and i'll show you a picture of that where they connect the haversian canals they're called volkman canals we have haversian blood vessels in the perversion canals we've got volcan blood vessels and the bulkman canals and then we got the lamellae which are those concentric rings the lacuna is where the osteocytes are they were once osteoblasts that painted themselves into a lacuna and now they're known as osteocytes the canaliculi are those little rivers that come out of the lacuna that allow the nutrients to go from the osteo i'm sorry the osteonic canals or the virgin canals of the blood vessels that carry the nutrients into each lacuna which has an osteocyte so now you're looking at this that little monolith model i showed you there's the medullary cavity you'll see the endosteum on the side there but you'll see the spongy bone this is one aversion system but they're all over here concentric rings are in there this is similar to the model i showed you here's the version blood vessels going through the virgin canal and then you got ones that go like an h these are the volcan canals that have the volkmann blood vessels that connect the hebergian blood vessels bone is very vascular which is why it'll actually heal faster much faster than cartilage six to eight weeks usually this is a close-up of the lacuna right so this is a habergian canal there's a lacuna and you can see all those kind of liquid light coming out spongy or cancellous foam makes bone lighter right they're more like those loofahs i was telling you about so it contains these are consists of these trabeculae which you've seen with the bone i just passed around there's no blood vessels in here the canaliculi connect to the open cavities rather than aversion canals do that's how it gets its nutrients through these canaliculi in spongy bone so spongy bone looks like this if this is your skull you got two compact bones on either side sandwiching the spongy bone in there and all those lines in there are what we call trabeculae this is just a close-up of it spongy bone is in the ends of the bones now looking at the trabeculae it looks like it's haphazard but it's not they actually are in an organized fashion dealing with all the mechanical stresses that the body goes through where there's more pressure more stress then as they grow because they keep on changing like the way you put a plant on the uh on the windowsill they will tend to lean towards the sunlight then you trick them and say okay you want to play games i'm going to turn you around you're going to face that way somehow it bends right towards the sunlight again right same thing with here the trabeculae if there's going to be more pressure it's going to create more it's going to follow that that's those stress lines where there's more pressure to make it more sturdier and this can change it could realign itself and it could change the way your femur is your thigh bone it's not straight in a person when you're looking let's say you're in a skeleton here they're going this way so what's happening here is that the stress is not going to be perpendicular here with with the bone itself it's going to go perpendicular to the floor not to the bone so you can see it's not going this way it kind of bends this way another way i could actually show you this is if you're a runner and you've been running for let's say i don't know three years you're jogging and doing you're a big hero you're training for the olympics you're putting more stress on your leg bones are you not every time you land on your foot bam bam bam bam bam so the spongy bone is going to get more it'll go towards where the stress is so you don't break your bones over there does that make sense it just does that then you decide you want to take anatomy and physiology with me you're not running as much you're sitting down a lot more so now the stress on your bones has been altered not much stress is on your legs so the spongy bone is going to start changing the trabeculae is going to start changing form to where the stresses are your butt bones will be actually a little bit more stronger because it's holding up your whole body you see what i'm saying so it changes it doesn't change overnight it changes a matter of you know weeks and months and it adapts to that so you have this bone remodeling it's always replacing old bone with new bone because it's dealing with these mechanics new mechanical stresses that your body's doing every day your bone is not the same it was five years ago it's different and it's doing this because it's doing all new uh stresses five percent of bone is remodeled each year on a normal basis there are two types of people that are these are two examples like there's probably a lot more but there's two examples that aren't going to do this people who don't have the stresses on their bones bedridden people they're just lying there in the bed their bones are not going to be strong there's no stresses on it does that make sense what about astronauts they're up in space there's no gravity up there there's no stresses on the bone they are at risk of getting osteoporosis so while they're up there if they're up there for a month they have to i'm just guessing i i know they have to do this i just don't know how long but they have to go maybe i don't know four hours a day into an area that has gravity and they have to sit there and read a book or do whatever work they have to do so that their bones have some kind of pressure on them so that when they come back to earth they don't you know even though they have a 30 year old body but their bones are like you know 100 years old they have osteoporosis okay so bones will always remodel itself due to these mechanical stresses that are put on them every day hint hint you do need to know that whenever i say hint there's got to be a question on the test i can almost guarantee that okay so the stress is unusual they get deformed for instance let's say for some reason my legs get amputated so now i start walking on my hands now my hand since the way i'm walking my bones are going to start growing in a weird way because it has to deal with new stresses does that make sense so it starts growing in a different way to start getting deformed but it's to deal with the new stresses now my hands have to hold up my body not like my legs anymore so it starts doing that okay