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BIOL 2301 Human Anatomy & Physiology I - BIOL2301 lecture09_0215
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00:03 All right, good morning y'all. Today, our discussion is gonna be
00:07 what bones are, uh really what tissue is, what its makeup is
00:13 ultimately what the structure of bone All right. So it's not actually
00:18 , it's actually more of a physiology of lecture. And then what we're
00:23 to do on the next lecture is we're going to go into the skeletal
00:26 and we'll start naming all the bones doing the knee bones connected to the
00:30 bone, yada, yada, yada . All right. And so just
00:33 that you understand when we talk about in general, we're not just talking
00:36 bone, there's actually a whole bunch stuff that goes with skeletal. So
00:41 and ligaments and there's other connective tissues are involved, but we're ignoring those
00:47 one reasons. How's that? All . So what I want you to
00:53 today and again, I'm going to reiterate this, remember, big picture
00:57 , what am I trying to learn ? I'm trying to learn about what
00:59 is and how it's structured and what does or how it's made. And
01:02 we're going to deal with that And so you should be coming right
01:06 class. First chance you get is , all right, just sat through
01:09 hour and a half long lecture. need to reorganize my information and we
01:12 to organize my notes. So it's easier for me to study because 30
01:16 suck. 2 to 3 pages of are easy. All right. And
01:20 a pattern that you should be developing help you be successful. All
01:24 So what is a bone? It's primary organ of the skeletal system.
01:29 have about 216 bones in our So we have 16 bone organs or
01:35 bone, not 16, 216. when you look at a bone,
01:39 need to think that's an organ, doesn't seem like it, but that's
01:42 it works. All right, it the framework for the body. So
01:46 are shaped the way you are shaped your bones dictate that third, the
01:53 cavity of the bone is primarily connective . And this connective tissue was referred
01:58 as red marrow or yellow marrow. get to what that does, but
02:02 doesn't play a role in building It actually has a completely different
02:06 It's responsible for producing your blood We refer to it sometimes as osseous
02:13 . And there are two basic types organizations to this osseous tissue. We
02:17 this type of bone that we refer as compact bone. So when you
02:21 of a bone and you look at bone, what you're usually looking at
02:24 on the outside and you're looking at compact bone, it's very, very
02:28 . Sometimes it's referred to as dense compact, it is white, it's
02:33 , it's smooth and it makes up 80% of your total mass of all
02:37 bone. All right. So it's . and then on the inside of
02:44 bone at the outside is this compact . Then the inside is this spongy
02:49 . All right. And spongy bone by some other names called uh cancerous
02:53 trabecular trabecula are basically lines of, materials or, or streaks of materials
03:00 strings of materials. And so that's the name comes from. And so
03:05 this looks more like a sponge. the name, it's very poor.
03:08 looking, it's very light. So only makes up about 20% of the
03:12 mass. So when you pick up bone, when you feel its
03:16 you're primarily feeling the heft of that bone and less of the spongy
03:21 Now, in this next picture, going to be seeing two different structural
03:25 . All right. And we're not to learn those just yet, but
03:28 going to use them as examples. we can see where these different types
03:31 bones are. And of course, have to click over here to make
03:34 work. There we go. All . So over here on this
03:38 this is going to be an example a long bone over here. This
03:41 an example of a flat bone and going to see them back and
03:43 But I'm just showing you now so you can see this is not a
03:47 of that one. All right. when you look at a bone,
03:51 can see here, I'm just gonna of show you, you can see
03:54 you have this compact bone. It's on the outside. It's really clear
03:58 and then on the inside, there's spongy bone here. You can see
04:02 is the compact bone, there's compact on the inside. It's kind of
04:05 looking. So you can see relatively where these things are located.
04:10 when you look at a bone, you've ever had ribs, you guys
04:14 eating ribs. Yeah. If you like pork, there are things called
04:18 ribs. They're like awesome. The of meat on this thing is like
04:21 big and they're, you know, like being, it's like living in
04:24 Flintstones where you get the brontosaurus. . But if you eat ribs,
04:29 you noticed you get down to that little bit of meat and it's stuck
04:31 that connective tissue and you have to of grab onto it with your teeth
04:35 rip it off. Have you noticed or am I the only Neanderthal
04:40 No one's gonna say one way or other. You can say I'm a
04:44 or you can join me in the eating. Yeah. Yeah.
04:50 When you're ripping that connective tissue off your teeth, what you're doing is
04:54 dealing with the connective tissue that's attached the outer layer of the bone.
04:59 that connective tissue is called peri Peri means next to ostium to the
05:06 . And what it is is it's a layer really two layers of of
05:11 material, the inner layer, the nearest the bone is going to be
05:17 bunch of osteopro git cells, osteo per generator making. So bone making
05:25 and what their job is for the part is to build that bone on
05:30 outer side. And then on the side, the the part that's nearest
05:35 you when you're looking at that that is that fibrous layer. So
05:39 is connective tissue that we're more familiar . So when you're ripping at
05:43 that's really what you're ripping at. then you have this really, really
05:45 layer of, of cells that are nearby and then the fibers don't just
05:52 around the outside, they actually penetrate the bone and hold that connective tissue
05:57 place. These are referred to as fibers. And you can see in
06:01 little cartoon here, they're trying to you the periosteum and you can see
06:05 fibers penetrating downward. And so like you're tearing that connective tissue with your
06:10 , what you're doing is you're literally off a layer of connective tissue that
06:14 internally intact or just is adhered to surface by those perforating fibers.
06:20 this layer of connective tissue is there protect the osteopor generator cells as they're
06:25 along. So this is on the of every bone, every bone has
06:29 the outside a layer of connective tissue then on the inside, which is
06:33 going to be clear here. And picture doesn't do a good job of
06:36 either is in the areas that's inside bone is we have another layer of
06:44 tissue. It's really primarily just these . So just like we see these
06:49 here, these cells are there. really obvious when you look inside this
06:54 a microscope, the cells are on surface in that open cavity. They're
06:58 found within the spongy bone. And are the same type of cells.
07:02 osteopor generator cells and other types of cells that include the osteoblastic osteoclast,
07:08 we'll get to in a moment. right. And their job is to
07:12 sure the bone is doing its All right. So when you think
07:18 bone, bone is not a dead , it's a very alive tissue.
07:23 has cells that are constantly remodeling and . All right, during your
07:29 up until about the age of 22 24. They are building bone and
07:34 bone bigger and bigger and bigger. a point where it stops growing.
07:37 around that age. Some of you growing around 15. I apologize for
07:41 . That's not your fault. That's your genetics, you know? But
07:44 are some people who grow until they're years and years ago I worked for
07:49 basketball program. I had all the players that um I would help uh
07:54 study and learn and stuff like So it's kind of a tutoring program
07:57 the athletic department and all basketball Um I was in the elevator once
08:01 four of them, they were all . One was 6 ft 11,
08:05 was 6 ft 10, 1 was ft seven. And here I am
08:08 a comfortable 5 ft nine maybe. I felt like I was in a
08:14 and all of those four freshmen were growing. One of them finished out
08:19 7 ft two played in Europe. not that it matters. All
08:25 So bone has connective tissue on the . It's a living tissue. There's
08:30 that are there that are involved in uh growth and remodeling. We're gonna
08:37 first at a long bone in a generic sense. All right. So
08:41 gonna use this model and I promise , you'll probably see a question that
08:45 with structure with a picture like So if you want to put a
08:49 star and say probably no, that's a good thing. So, and
08:53 , and I will add here and , I'll come back and say this
08:57 . I'm not gonna ask you questions you would see in a lab
09:01 Does that make sense? Right. I'm not gonna have you try to
09:05 parts of a bone unless it's really, really, really obvious.
09:10 that make sense? And the reason is that lab classes allow you to
09:14 up bones and hold on to bones if you want to, you can
09:17 them, don't do that. All . But the idea here is we're
09:22 with images like this in a lecture . So we're going to limit ourselves
09:27 what we can do in a lecture . All right. So with the
09:31 bone, long bone is longer than is wide. So you can see
09:36 you think about a bone. For most part, you probably think about
09:38 long bone, long bones have three parts to it. It has the
09:42 portion, the shaft, that shaft what we call the diaphysis,
09:48 The diaphysis has to it, an cavity you can see here that is
09:55 . So if you go take a bone and cut a cut it cross
09:59 through it, you would see that could stick your finger in there.
10:02 , kind of that hollow area is filled with marrow when you're a young
10:08 , that marrow is red marrow and eventually changes over to yellow marrow.
10:12 right, and yellow marrow is primarily predominantly fat. So that connective tissue
10:17 there is predominantly fat as you get , it switches over. All
10:23 The purpose of the diaphysis is to a weight supporting or weight bearing
10:30 It's what you use for locomotion. it is a structure to which muscles
10:35 attached at different points to provide leverage movement at the ends of the
10:43 These are called the pith thees, plural. Epiphysis is singular. So
10:48 you hear epi again, epi means . So they're just saying above or
10:52 the ends of the bone. So pith is here, here is the
10:57 pith. This particular one bone that looking at is a femur femurs look
11:02 than other bones. So it's not the same thing as your humerus or
11:04 of the others. But you will that an pith is simply the region
11:08 the end. When you look in end of a uh pith isis,
11:13 you'll see is that it's not hollow the diaphysis is instead it's filled with
11:18 bone. The spongy bone has within . Red marrow for the most
11:22 although it will be replaced by a bit by a yellow marrow. All
11:26 . And on the ends you can here, it kind of the cartoonist
11:32 of made it kind of smooth and . And the reason it's smooth and
11:36 is on the outer surface of the . This is typically where your joints
11:40 . And so this is a joint where two bones meet. And typically
11:45 a long bone, these two joints not just meeting, they're actually moving
11:49 each other. And if you didn't a protective surface on it, those
11:53 bones would grind each other down. what we have is we have a
11:58 smooth surface. This is called a uh articular cartilage. So that's what
12:04 see here is cartilage, that's cartilage it allows the two bones to smoothly
12:08 against their surface or the surfaces move each other without grinding down. Here's
12:16 weird one, it's not labeled on . And if they did, they
12:19 a poor job of it. Do see this region here? Of compact
12:25 ? Everyone see that? OK. there it is up there as
12:30 That region sits between the pith isis the diaphysis. Notice that the cartoonist
12:38 just puts lines up there because the illustrator didn't know what he was
12:43 he just drew pictures and basically found he could do that region. So
12:48 can just kind of like circle this kind of circle that is referred to
12:53 the metaphysis. It's the transition point the epiphysis and the diaphysis and the
12:58 reason I'm pointing it out is because that metaphysis is a structure called the
13:04 plate. This is your growth All right. And while you are
13:09 , very young, the epithelial plate primarily cartilage. And so as you
13:15 , this is where growth occurs. as you're growing taller and taller and
13:19 , that is car cartilage. And you're doing is you're laying down bone
13:24 you're laying down cartilage. But what up happening is is that the bone
13:27 laid down becomes faster than the cartilage down and it catches up and it
13:33 the cartilage and it ossifies. And that happens, you're left with this
13:38 remnant structure that is of compact bone that's when you stop growing. So
13:44 back to when you're 8 to 10 old and puberty hit, maybe it
13:47 12, maybe it was 14. a little bit different. But around
13:51 ages and you went away, you , you went home for the
13:54 maybe that one that uh from school summer and then you came back and
13:57 you knew was like eight inches taller you, right? Ok. So
14:01 happened was that was growth in the plates. So they start shooting up
14:07 then when you stop growing, that's that pius plate closes. It's
14:15 the cartilage is replaced by the We're going to describe this process at
14:18 end of class. So long bones structures. Diaphysis shaft epiphysis ends in
14:25 metaphysis. That's where the growth plate located. Then we have all the
14:32 bones and there's a lot of other . So the other bones are referred
14:35 as the short bones, the flat and the irregular bones, they have
14:38 slightly different structure and you can kind see it here represented through our uh
14:43 bone. So what do we We have an external surface that is
14:47 . So just like the diaphysis, has compact bone and then just like
14:52 ends, the epiphysis, it's filled this spongy bone. We call
14:56 we give this spongy bone a special . We call it diploe. All
15:00 . Why we call it diploe? don't know it's diploe. All
15:05 There is no medullary cavity. There no open space. But you can
15:09 otherwise we still have the periosteum. then inside that spongy bone, we're
15:13 have those osteopro git cells. All . So all the other bones don't
15:20 the open space is the really the thing here so far, everybody with
15:26 . All right. So structurally, are pretty simple until we get down
15:30 the nitty gritty. In terms of , we say bones have four different
15:37 . We're gonna have the flat we're gonna have the long bone,
15:40 short bone and the regular bone. then your book likes to point
15:42 oh, look, we have these bones called sesamoid bones. When you
15:45 sesamoid bone, what do you think sesames? Right. And really what
15:50 is a sesame seed. So, are bones in your bodies that are
15:54 bitsy, teeny, tiny that are worthy of giving a name. And
15:59 are shaped like little tiny seeds and all over the place. All
16:03 And when you look at the I'll even when we do the
16:06 I'll point out, look, here's couple of sesamoid bones. They don't
16:08 have names. We're just gonna ignore . They don't exist. All
16:12 But I'm pointing them out because your points them out. All right.
16:15 first flat bones, why do we them flat bones? They are,
16:20 it louder. They are flat. you go. So it's really kind
16:24 easy to look at them. You're you look at the bone, you
16:26 , is it flat if it's Yeah, it's a flat bone.
16:29 as simple as that. All They will be slightly curved because nothing
16:35 this world is simple, right? is just flat and easy. They're
16:39 have a slight curve to them. gonna, their job because of their
16:44 is to protect underlying soft tissue. , the example of a flat bone
16:49 be those bones that make up the vault. All right. Do you
16:53 where your cranium is? That's All right, good. So,
16:57 vault is the roof the floor would what you can't see. But all
17:02 bones that make up the top of skull are flat bones. That would
17:06 an example. All right, there's ones, the scapula. All
17:10 So the scapula is the bone back . The sternum is one that sits
17:14 the middle and those all make sense you look at them. But a
17:17 of people think about the ribs and , oh, the ribs are long
17:20 because they're longer than they are And it's like no, if you
17:23 at them and hold them to the , you will see that they're
17:27 they have a long curve to but they are flat bone and the
17:30 way to see them is again, out to your favorite barbecue joint,
17:33 order a thing of ribs, eat meat off the bone and then look
17:36 the bone and you're gonna see that is a flat bone. It's easier
17:41 you look at a cow bone, is much, much bigger than a
17:43 bone. All right, as I , sesamoid bones, these are
17:50 They're really kind of a subgroup of short bones. Typically they're small,
17:54 and oval shaped, they're put in where they can provide extra leverage.
18:00 , the most, the only sesamoid that I know of that we learn
18:04 has a name and I'm sure every of them does have name. This
18:08 biology, right? Everything is gonna named at some point. Right.
18:12 the one that we are familiar with your patella or kneecap, right?
18:16 , you're all familiar with your And if you look at it it's
18:18 , oh, yeah, that's kind flat and round. It's about this
18:21 , right? Oh, ok. that's a sesamoid bone. It's this
18:25 shaped thing that sits in the muscle allows me to lift my leg up
18:29 the muscles of my thigh pull on and wrap around to lift up my
18:34 leg. The long bone, we've seen a picture of they're all typically
18:40 than they are wide. They have cylindrical shape to them. So notice
18:44 distinction here is they're not flat, cylindrical for the most part. All
18:50 , is the most common bone When we go through the system you'll
18:53 seeing. Oh, yeah, here's long bone. Here's another long
18:55 Here's another long bone. And the thing is they are predominantly found as
19:01 of your appendices. All right. your appendices are your arms and your
19:07 . So, with very few most of the bones in the upper
19:12 lower limbs are long bones. Even fingers are long bones. The only
19:17 ones are the ones in your Short bones roughly have the same length
19:24 they are wide. These are the that are found in your wrist.
19:28 these are your carpals and your tarsal . Again, if you don't know
19:31 these bones are, don't worry about gonna get to them all. All
19:34 . So, uh again, the bones fall into this category. Um
19:40 , um So if you kind of at a bone and go,
19:42 that's roughly the same width and same , that's probably a short bone and
19:48 last group. Um And it, , it's a category into itself just
19:53 when you look at these bones, don't fall into the other three
19:55 It's like, ok, this is long, this has a weird shape
19:59 it. It's not square, it's um flat, it's just weird.
20:04 it falls into the irregular category. right. And so these are gonna
20:09 like your vertebrae, the bones of skull and the hip bones. And
20:12 would think, well, aren't the bones really a flat bone? And
20:15 like, no, it's actually a of three bones. It gives a
20:18 , we weird shape and that's Yeah. Um Not really.
20:26 Usually you just kind of classified as type, right? So the question
20:31 apart from the seso, do anyone fall into other categories? And the
20:35 is no, it's, this is the only one. All right.
20:40 what I want to do is I to point out some features here that
20:43 not going to test you on. . So that doesn't mean turn off
20:48 brain. It's to alert you that something that you need to know,
20:52 I'm not gonna ask specific questions All right. So all your bones
20:57 unique features to them. All And it's part of the way that
21:00 identify bones and you use those bones to understand how movement works. All
21:05 , they have what we refer to being markings to them. All
21:09 And when I say a marking, is the purpose of marking?
21:13 they provide the characteristic for that bone do its job. And there are
21:17 types of bone markings. And so way that I would test you on
21:21 is not ask you what is a , what is a fossa or a
21:24 of groove? All right. I want you to understand what is
21:28 depression? All right. So these all examples of depressions. They're basically
21:35 where bone meets bone, blood vessels nerves are going to be traveling or
21:38 two bones are going to articulate. they have unique names based upon the
21:44 of shape that they have. So don't think the important part today is
21:48 what those unique names and shapes It's just when you come across
21:52 you should say, oh, if see fossa here, a fossa is
21:56 type of depression. And what is depression doing? Now again, this
22:01 more important than the laboratory when you're there looking at a bone and you
22:05 see that depression, right? But you're looking at a picture like
22:10 it's really hard to see that isn't it? So I'm not going
22:14 sit there and go name that right? Or name that structure.
22:18 right. So the idea here is are things on bones that are depressions
22:23 when depressions are there, that means some sort of interaction between the two
22:28 or a bone in another structure like blood vessel or a nerve. That's
22:32 key thing. There are other types bone markings like openings. These are
22:39 in the bone. Why would you a hole in your bone? Seems
22:43 a weird thing to have. sometimes something has to move from one
22:48 of the bone to the other. about your eyes. What are your
22:53 connected to in terms of tissue? where does it send its signals to
22:59 brain? All right. But you a skull that sits between your brain
23:04 where your eyes are. And so needs to be a way for that
23:08 nerve to get to your brain or your eye depending on which way you're
23:13 . So holes allow for the passage something between the two points on the
23:18 . All right. So we have like meats. I know you look
23:23 it and you're like me, I say me, but it's a
23:27 Uh here's the rule, you can anything the way you want to in
23:32 class. All right, because even don't know, I mean, I'm
23:37 to me don't know the names of properly and just to prove this,
23:42 go to a conference every year for MP professors where we talk about all
23:45 of fun stuff. One of uh, authors of the textbooks,
23:50 of the most popular textbooks gives a to teach you how to say things
23:55 he teaches it like a jeopardy It's like, how do you pronounce
23:59 word? And then he'll pronounce it four different ways. And you'll have
24:02 different professor sitting there raising their hand how they pronounce it. Then he'll
24:05 you the proper way to pronounce It's the most embarrassing class you'll ever
24:08 . But it's a lot of fun we are laughing at each other because
24:11 a bunch of idiots. But there is, he ate us. All
24:14 . We have like things like a . And you can see here this
24:17 a temporal meatus. This is where auditory canal is, is how sound
24:21 your ear gets into the inner For example, you have other structures
24:27 a Foramen, a plural for Foramen Foramina. Foramen means whole, literally
24:33 hole. We're gonna learn here a bit about the Foramen Magnus. What
24:38 you think Foramen Magnus is if, Foramen is whole what do you think
24:43 means? Magnus? Come on Do you see how well we name
24:51 ? It is called the big All right. Good to know the
24:58 hole. Great. All right. these are again, again, a
25:02 and there is an example of the, the orbital fissure right
25:05 that's through which the optic nerve But again, I'm not gonna ask
25:09 to identify these just when you see words, that's what they mean.
25:13 right. And finally, we have , projections by, by their definition
25:18 something that points outward. These are that are gonna have different shapes and
25:22 where muscles or tendons or ligaments are attach to that bone. In other
25:28 , it's a point of attachment and all sorts of different types of points
25:32 attachment. I mean, you can here, I mean, we've got
25:35 , five here and then we have five there. All right. And
25:39 gonna see these names over and over . Condyle, you're gonna see a
25:42 . We have a structure called an . What does epi mean above and
25:49 condyle. So it's just telling you is it? It's above the
25:52 that little bump right there on your . That's an Epicondyle. Why?
25:58 it sits above the condyle. What the condyle? It's a point of
26:03 ? Great. All right, we crests, we have heads tubercles and
26:08 . We have epicondyle there. That's epicondyle processes, spines, protuberance,
26:14 lines, many of these look look words that mean to project some of
26:19 . It's like, like pro I would have no idea what it
26:21 . I'd have to look at it a while. But when you see
26:23 terms, what you need to think is something is attached here, something
26:28 a ligament or a muscle is attached this point and it's gonna promote some
26:33 of movement. That's the key So bones have characteristics, different types
26:41 it helps describe what this bone is for. Yeah. All right.
26:48 marrow versus yellow marrow, someone has the head off. So this is
26:54 what you're looking at when you're looking an epiphysis, they've cut off the
26:58 and you're now looking into it and can see here all the spongy
27:02 you can see the spongy bone. right. Yeah. OK. And
27:04 can see right here, this would an adult. You can see that
27:07 have some yellow marrow and then everywhere , it's nice and bloody red,
27:11 red marrow. It's just showing you is the stuff found? It's right
27:15 in that dip Loy, it's right in that uh hard to reach spot
27:19 the epicondyle. So marrow is a connective tissue. Its function when you're
27:25 with red is that it's hematopoietic, is a really, really fun word
27:28 try to spell on an exam. right. Especially if you try to
27:32 the British spelling where you throw an and an E together and jam them
27:35 . All right, hematopoietic means blood or blood derived. It's basically where
27:42 blood cells are being made. So a blood factory. All right.
27:46 your red blood cells and your white cells are formed in the red
27:51 All right. Now, where do find this? Well, when you're
27:54 kid, if stuff is everywhere. right, because you're in a constant
27:57 of growth and you're constantly producing blood as you're growing. But as you
28:02 , you don't need to do this so much. And so that red
28:05 gets replaced by the yellow marrow and red marrow um basically becomes isolated in
28:11 very specific locations. And these are be primarily in the diplo of the
28:15 bones. If you've ever known someone ever gone and donated marrow, you
28:20 to go give them a high five buy them ice cream or something because
28:24 get to that marrow, you have go through some horrendous surgery.
28:29 let's say you have to drill through . That's exactly right. So imagine
28:33 have to drill through and get to epicondyle then just to suck a little
28:37 of red marrow out of that. that's why I say buy them ice
28:41 because ice cream makes everything better. ? Hard places to reach young
28:49 easy peasy. You just cut them . You can get marrow pretty much
28:52 you want the yellow marrow. On other hand, this makes me sad
28:56 primarily adipocyte. So that means in my bones, I got nothing but
29:01 . So, except for where the marrow is located. So just another
29:06 to look forward to is your body starts replacing all the good tissues with
29:10 . Great, thanks. All Now, let's say you're in desperate
29:16 of, of blood. Well, body will ramp up uh red blood
29:21 production and it will start replacing that marrow with red marrow for short periods
29:26 time. So far, everybody with , this is pretty straightforward stuff,
29:31 it? I hope. Ok. right. Now, what we're doing
29:35 we're gonna start shifting gears. We're ask the question, what are the
29:38 that exist inside? Bone? Bone living tissue, right? It is
29:44 type of connective tissue. So it's lot of fibers. We're going to
29:47 with the fibers in a moment. that means we said in connective
29:50 we have cells plus fibers. And what kind of cells exist there?
29:54 , the cells are all listed We have the osteopro git cell or
29:59 cell. It's the stem cell that rise to the osteocyte and the
30:04 And then we have another type of that is uh not related to this
30:10 of cells but it resides in the . It's called an osteoclast. All
30:14 . Now, I'm gonna just teach some real basic nomenclature here. Um
30:19 so that you understand, I've already it once when we talk about the
30:22 tissue, but it may have gone your head. Is that when you
30:26 a cell that has an end of name as blast blast, that is
30:31 immature cell? All right, it a cell that is doing something that
30:36 fully differentiated into its mature form All right. So an osteogenic cell
30:43 so genic at the end of a means it's gonna be a stem
30:47 Stem cells are are the least They can differentiate in all sorts of
30:52 things. Here, it says osteogenic I have not uh differentiated into the
30:57 form of the bone cell. an osteogenic cell gives rise to an
31:04 and then the osteoblast does something and when it matures, it becomes an
31:10 C ic yte at the end means mature form of the cell. So
31:15 we talk about connective tissue, you fibroblast fibrocyte, that kind of gives
31:18 a sense. Chondroblast chondrocyte, osteocyte. Do you see how we're
31:26 those words, immature and mature immature mature? So, in your bones
31:34 in that uh uh periosteum right on edge is you have the osteopor geneal
31:42 , these osteogenic cells, those two mean the same thing the osteogenic or
31:47 cell is the mitotic stem cell, it is the pool of cells from
31:52 we're going to derive new bone And we will need to do that
31:57 the bone is growing. All So here we can see this is
32:02 outside of the bone as it's being . This isn't quite bone yet.
32:07 you can see it is bone. what we've done is we've made these
32:11 cells that are gonna differentiate and become and the osteoblasts are gonna be responsible
32:20 laying down bone. They make the blasts, make bone osteogenic cells make
32:29 . Yes, ma'am. No. the osteoclast do not write this
32:37 I'm not gonna ask you this. are derived as a, as a
32:42 of macrophage. So their origins are different origin. So they're, it's
32:48 here we have my osteogenic family and over here we have the osteoclasts.
32:53 that's why I say I don't want talk about their origins. Just know
32:56 they're not related. All right, gonna have a different role. All
33:00 . And you notice I tried to them all on one page here and
33:03 one's missing osteoclast, right? osteogenic cells give rise to osteoblasts.
33:10 start laying down bone and when they down bone, they typically lay down
33:15 in all directions. The cartoon here showing you that they're laying down bone
33:19 this direction, but this is at end of the, or the,
33:22 the outer edge of the, of um bone itself, right? So
33:27 laying out layers in this direction. so they're kind of pushing the bone
33:32 from themselves. But typically, what happen is that as the osteoblast is
33:37 down bone in all directions, it trap itself in the matrix of the
33:41 that's laying down. All right. it's like painting, think about,
33:45 heard painting yourself in the corner. like painting on the floor and you're
33:49 in all directions. And the next you know, you're stuck, you
33:51 go anywhere. And that's what happens the Osteoblast. It, it lays
33:55 matrix in all directions and gets trapped when it gets trapped, that's when
34:00 differentiates and becomes an osteocyte. And purpose of an osteocyte is not to
34:06 sit there and eventually die. Its is to detect the stresses in the
34:12 that it created. All right. I've laid down a matrix as an
34:17 . Now, I'm watching for stress the bone. Now, when do
34:21 put stress on our bones when you're ? Right. So every time I
34:26 a step, I'm putting stress on bones. All right now. Is
34:31 a bad stress right now? What you think? No. All
34:34 But let's say I go because I'm at a bunch of guys here and
34:38 know how guys think they go to gym with a bunch of their friends
34:41 they haven't been working out in a time and they're like, look at
34:43 , I can go ahead and bench . Would you detect a stress in
34:49 bones? Right. Yeah. Every you move an object, move your
34:53 , you're stressing the bones. And they're doing is they're detecting to see
34:57 those stresses are going to cause damage the bone. And when it
35:02 it detects that stress and then it the other cells where it needs to
35:07 bone. So it strengthens the bone upon the usage of your bones.
35:14 every time you get up and walk , every time you move, every
35:17 you exercise, every time you do things, you're actually causing your bones
35:21 strengthen themselves. It's a good All right. So the osteocytes maintains
35:27 bone. It's not capable of making bone. It has to tell the
35:32 cells either to make new osteoblasts so can lay down new bones or what
35:36 gonna do. It's gonna to communicate the osteoclasts of the osteoblasts to tell
35:40 what it needs to do in order make stronger bone. All right.
35:45 , osteocytes maintain the bone osteoblasts build bone. So what does that
35:52 Osteoclast must do if I'm building the and maintaining the bone osteoclast, must
35:58 the bone, break down the Yeah. So, and it kind
36:01 tells you again, going back to origin. I said, well,
36:04 don't want you guys to know if destroy things, you know, and
36:08 things. What is an osteoclast It's behaving like a macrophage, but
36:11 focusing specifically on bone, it breaks the bone. So when you have
36:16 that you don't need osteoclasts, break bone down and make those materials available
36:23 recycling to rebuild your bone. All . So here's an example you can
36:33 here, here's the bone. What trying to show you is like,
36:36 , I'm releasing enzymes. It's breaking down because this piece of bone right
36:40 is unnecessary for structural support. is this really done on the surface
36:47 on the outside of a bone where where there's compact bone? Not so
36:51 ? All right, really? You're to see this on the inside where
36:54 have that spongy bone where you have I'm going to use that horrible
36:58 the trabecula, right? Those strings bone. And what you're doing is
37:04 can imagine those strings of bone are along stress lines and when those stress
37:10 are necessary or the those those trabecular unnecessary, I'm gonna just break it
37:14 because I'm not gonna waste the, the materials there. I'm gonna put
37:18 where, where there is gonna be . All right. So I break
37:23 bone that I don't need and then build bone that I do need.
37:27 with this process of breaking down bone called resorption. And this is kind
37:32 what it looks like. And this not the best picture. I just
37:36 something on the internet, but this of shows you the cycle that your
37:39 is going through. So you can , I built a bone. I'm
37:43 just start down here. I built through a process of formation. So
37:47 got Inky Binky and Clyde, you probably are too young to remember
37:53 Those were the names of the inky, blinky, pinky and then
37:59 . Yeah, I'm old. All , they built bone. This is
38:04 formation. And when do I do ? Well, when I have calcium
38:07 my body, my body doesn't want get rid of the calcium. I'll
38:10 building bone on those stress lines to and strengthen the bone. And then
38:14 happens is, oh I need calcium this bone is, and this bone
38:18 unnecessary. Then what will happen is I will bring in an osteoclast
38:22 then the osteoclast will break down the through this process of reabsorption. And
38:28 the hope is is that I didn't that bone, right? In
38:32 you didn't. But let's say, I'm, I'm now exercising in a
38:35 that this piece of bone no longer the stresses that are being applied to
38:40 . And keep in mind there is little tiny string inside your larger
38:44 Then what will happen is, is , oh, then I'll bring in
38:46 osteoblasts and they'll rebuild the bone. again, they're gonna do it in
38:50 a way where they might get trapped it. It's not literally Pacman Ghost
38:56 around on the surface of the Ok. So we have this process
39:01 is renewing bone all the time. breaking bone down and we're building bone
39:06 , breaking bone down, building a up all the time. And in
39:09 , I love the cyber. You need to memorize it, but it's
39:13 . We recycle 5 to 7% of bone mass every week. That means
39:18 20 weeks, you've recycled a hun of your bone by mass. That
39:23 mean you rebuilt all your bones, is by mass. So that is
39:27 lot of work 20 weeks. That you are rebuilding your entire skeleton 2.5
39:33 a year. It is a very organ system if you think about it
39:40 those lines. All right, spongy is where we're gonna see most of
39:45 work compact bone less. So because the way that it's structured so
39:51 everybody with me. So what we've so far, basic shapes of
39:57 how we make bone and break the cells that are involved in
40:01 And so we're going to shift gears and we're gonna dive down into the
40:05 structure itself All right. And this not always the easy thing to
40:11 All right. So we're gonna, gonna kind of keep pulling in and
40:14 back out, pulling in and moving out over and over again. So
40:18 you think about bone, bone has major components to it has an organic
40:23 and an inorganic component. And if some of you who've taken organic
40:27 you, you, you already are triggered by that word. And
40:30 just really simple here. Inorganic is calcium salts. So what you can
40:36 is I'm gonna start off with a of collagen fibers and some other ground
40:40 . So, so far that sounds normal connective tissue that we've learned
40:44 right? And so this collagen is be arranged in these long strings.
40:50 this is what we refer to as and in that osteoid, what we're
40:54 do is we're gonna add these calcium . All right. It's called uh
41:01 appetite is how you pronounce that. what you're gonna do is you're gonna
41:04 those salts on there. And so would be normally a real Bindy,
41:08 to manipulate? Matrix becomes a very dense and hard matrix. So
41:13 where, where we get the mixing the, the organic and the
41:18 Now, of course, the cells are organic. So they're gonna be
41:21 uh stuck within the matrix. And you can see here, what we've
41:25 is we're taking these, these molecules we're making this this stronger structure,
41:32 dense fiber, this hard structure. then we're going to organize that in
41:37 really unique ways. All right. so what you're not seeing here is
41:41 this, this these two things are , we're going to deal with that
41:44 just a moment. But what this is it provides a degree of rigidity
41:50 this, this structure and this inflexibility uh cartilage doesn't have. All right
41:58 , I'm just gonna use uh the in my nose so I can do
42:02 just fine, right? You can me at the end of my
42:05 I can wiggle it right up here where I have bone. When you
42:10 I broke my nose. That's what saying. You broke this, look
42:13 , I have no movement up right? So hard, immovable down
42:24 , soft movable. It hurts when smash this part, but you don't
42:28 anything. Get up here and smash . That's not a lot of fun
42:34 far, so good with this. right. So what we're gonna do
42:38 we're gonna back out a little All right, we're gonna see what
42:42 uh this material becomes this osteoid. the osteoid, these fibers which are
42:49 produced by these osteoblasts are gonna be in these structures called osteons. All
42:56 . Now, what we're looking at , this is the compact portion of
43:03 long bone. In the diaphysis. , um you see here, there's
43:08 peri uh periosteum. You see that here, that would be where the
43:16 is located. So this is the cavity. And what we're looking at
43:20 we're looking at a series of these which are the organization of these
43:26 And if you pull one of these , this is what they've done
43:29 we've pulled it out so that you see what it is is a series
43:32 concentric rings. And if you look it under a microscope, this is
43:36 you would see of this structure right . You can see that it's a
43:41 of concentric rings and the black dots where you have osteocytes stuck in these
43:47 tiny pits, it kind of looks a bull's eye. So in the
43:52 is an open space that open space blood vessels and nerves in it.
43:57 then you have a series of rings work their way outward like. So
44:01 you can see being drawn here. osteons which are made up of the
44:08 are the weight bearing structures of of compact bone specifically. All
44:15 And you can see their arrangement. line is trying to show you you
44:18 one moving this way and then the one on the inside, middle of
44:21 way and then the next one on inside moves this way and the next
44:23 will move that way. And so . And what you've now done is
44:26 created a cross weave of structure, means not only does it have compression
44:32 , but it has torsion strength as . Anyone see the movie The Blind
44:37 ? Because I know you're all way young to have seen the original.
44:40 you see anyone see it? You guys need to get out
44:43 All right. It's a story about Orr, Michael Orr was a monster
44:49 a man. Even in high he ended up being a professional left
44:54 and the whole point of blindside is he protects the quarterback blindside. They
44:58 up the movie from a game uh, between the Redskins and what's
45:04 longer you in the Redskins? You old this is, right?
45:07 but back then it was the Redskins it was, um, the New
45:11 Giants, Lawrence Taylor was a linebacker the New York Giants and the quarterback
45:17 the Redskins was Joe Theismann. His name is Joe Theisman, but they
45:21 him, named him Theisman because All right, if you want to
45:26 into Heisman, Joe Theismann is rolling Lawrence Taylor was a phenomenal linebacker.
45:32 mean, he was mean and strong just awesome. And what he does
45:37 he's chasing down on the blind side Joe Theismann. Joe Theismann's,
45:41 uh, rolling out and he um, Joe Theismann by the
45:47 plants Theismann's ankle down on the grass then does whatever every good linebacker should
45:53 . He rolls over like a But because that foot was planted,
45:58 had no place to go. And he did was he broke Theismann's leg
46:03 the most horrific way possible. And watched this live. It was
46:08 He basically took the leg and twisted and it broke as if you were
46:13 something like so. So think about . If you're to take a handful
46:17 spaghetti and twisting it and breaking that's what he did to Joe Theismann's
46:21 . All right, your leg is supposed to do. That shows you
46:23 strong Lawrence Taylor was. Lawrence Taylor got up and pointed to the sideline
46:28 said, come over here, I this, I heard it and it
46:32 horrific and that was the end of Theismann's career. That's what this
46:38 All right. It just shows you get enough strength, horrible things
46:42 happen. All right. So osteons a res uh that resistance to torsion
46:51 because you have so many of See, it's not just one,
46:54 got hundreds of these that are making the compact bone. Now, each
46:59 these osteons have structure to them that have to learn the nomenclature for.
47:04 right. So we're going to focus just one of these even though there
47:09 hundreds of them. OK. So you can see, we're now looking
47:13 one of these osteons. All So I pointed out we have this
47:17 space in the center. So there could see that hollow space. This
47:21 called the central canal, central canal where you're going to find the blood
47:25 and the nerves of bone. So do we need blood vessels in
47:30 Well, we've got a bunch of cells in the bone. We have
47:33 these osteocytes. All right, the you can see in the little cartoon
47:38 like the little tiny bugs everywhere. what they are is they are living
47:42 that are stuck in these little tiny called lacuna. When I see
47:47 I think lagoon or lake, it lake. All right. So this
47:51 a watery environment. You can see osteocytes stuck in it. And what
47:55 doing is it's sending out extensions out these little tiny canals called conic.
48:01 that's what they're doing is trying to you. And so this osteon or
48:04 , this osteocyte is talking to that which is talking to this osteocyte and
48:08 on and so on and so So all these cells are talking to
48:11 other and they're sending nutrients to each via these connections and through the connections
48:18 these canicule that are too small to see in this picture. All
48:22 So the blood is releasing the nutrients that all these cells can stay
48:28 And the earth is sitting there just the strength of this osteon and it's
48:32 ability to do so. All Now, the osteoid, the material
48:38 makes up this structure has a All right, we call it collectively
48:43 circumferential or sorry. Concentric. It's circumferential. Concentric, lamelle, lamelle
48:49 sheet. So it's just a concentric sheet. And so you can think
48:54 got a central canal, then lamella, Concentra, concentric,
48:59 so on and so forth outward and the boundaries of each of these
49:02 that's where the osteocytes are gonna be . So this is a good way
49:06 kind of see it. This is you if you looked under a normal
49:10 . That's what you would see. can see the little black dots represent
49:13 lacuna containing the osteocytes. And here is a scanning electron micrograph. You
49:18 see how their pits and you can that would be where those cells are
49:22 residing. Now, if you take bunch of these osteons, you can
49:29 we have a bunch of them, ? So if we have a bunch
49:31 these osteons, we're basically wrapping them . It's like taking a bunch
49:35 of straws or a bunch of pencils you're wrapping them with rubber bands.
49:39 so the thing that you're wrapping them have special names and it's still the
49:42 material. It's still osteoid, but osteoid on the outside is being laid
49:47 by the osteoblasts that are on the , which is just underneath that periosteum
49:55 part of the periosteum. And so we refer to that layer on the
50:00 . So you can see here, have these sheets that are being formed
50:04 those osteoblasts, those are called circumferential . All right, there's one on
50:11 outside and there's gonna be one on inside. The one on the outside
50:16 external, the one on the inside internal, so pretty straightforward. So
50:21 is how we're kind of creating that outside. And this, what we
50:26 is a smooth on the inside, that we're gonna see that we're gonna
50:30 this spongy structure as well. But you have a round structure and you
50:36 it next to another round structure, is the next round, another round
50:39 . Are you going to have space between those things? Yeah. So
50:43 need to fill that up. And we have a name for that as
50:45 . That's interstitial lamellae. And you're gonna have osteoblasts that lay down
50:50 material, which is osteoid and it's laying it in between. And so
50:54 just filling up the material. we can do it one of two
50:59 , we can actually tear down one these osteons and then rebuild a new
51:03 . And so whatever is left in that would be interstitial or if there
51:07 a gap, then osteoblasts would fill gap up. So either of those
51:11 ways is how we're going to get lamella. But this is how your
51:15 is structured. You're basically you have and you're wrapping the osteons in more
51:21 . See how the two names can . Kind of confusing Osteoid is the
51:25 osteon is the structure. So, I confused you all at this
51:33 There's one other canal you need to familiar with. I can't get a
51:36 vessel in the central canal unless it its way through. And so that's
51:40 we call a perforating canal. just to remind you that this is
51:46 . Have you ever been kicked in shins? Whether by sibling or a
51:50 does it hurt? Yeah. It only hurts if there's a nerve
51:56 . So just think whenever I bruise shin, whenever my bone hurts,
52:00 hurts because there are nerves and there nerves because this is a living
52:05 All right. So that's why you the nerves that are traveling.
52:08 and just in case, I know su I'm sure I told you
52:10 red means vein blue means artery or , backwards, artery means red.
52:15 means artery blue means vein yellow is , always, always nerves.
52:23 So osteon is what makes up the bone, osteons are made up of
52:28 . There's different nomenclature to that this uh concentric lamella, um the
52:35 , the canicule and then on the circumferential, on the inside circumferential.
52:40 one's internal, that would be external would be on the outside.
52:45 who makes the asteroid? What type cell blasts good when you get spongy
52:52 . It's very similar, but it's exactly the same. See,
52:58 the uh trabecula have that same There's no central canal and you don't
53:03 a central canal because it's not so away from the surface. So,
53:08 you'll still have these lacuna, you have uh osteocytes that are trapped in
53:13 lacuna. You can still see the lamellae, but really any sort of
53:18 work their way through the little So the little linings that you see
53:21 , those are the canicule, there's blood vessels necessary because materials move in
53:26 out through the little tiny holes of canicule and they perforate into where the
53:33 are. And you can see out on the surface of the trabecula,
53:36 do you have? Well, those the osteopor cells, plus the
53:40 plus their neighbors, the osteoclasts. what we're gonna do is we're gonna
53:44 and break down bone along these For the most part, this is
53:48 it's pre predominantly taking place. So we talk about endosteum, that's what
53:53 talking about is just the materials surrounding trabecula. And when you talk about
53:58 you're inside that medullary cavity inside the bone, you're gonna see these
54:03 right? We saw them over here if you're in the epiphysis or if
54:09 in that diploe, this is what's on. It's open lattice work like
54:16 looks like sponge and they're being built stress lines. And so the osteocytes
54:23 detecting the stressors in that bone. me just standing here, I'm creating
54:31 . The weight of my body going is stress so far with me,
54:37 moving pretty good, aren't we ready get down to the last little
54:42 How do we make bone? All . So we know what's being
54:46 How does this go about doing You began life as one cell.
54:50 did your bone come from? There's different mechanisms that are in play
54:56 All right. So the first type called intramembranous. All right, without
55:01 anything else, what do you think means inside a membrane? Well,
55:07 membrane? Well, I've not taken . So I won't know. But
55:12 you have this material called mezzanine and mezzanine gives rise to the skeleton plus
55:19 whole bunch of other stuff. All . But that's where it's coming
55:22 So, what we're gonna do is gonna use that mezzanine as a place
55:27 we're going to build stuff. And the second type is called endochondral.
55:31 means inside Conro is cartilage. All . So Endo cartilage inside the
55:42 So what we're gonna do is we're create a cartilage framework and we're gonna
55:45 that as our model and we're gonna our bone on top of it.
55:49 the idea. OK. So right , it just kind of shows you
55:53 there's two types. Now, most the bones like your long bones and
55:57 , we're gonna use endochondral, but flat bones are gonna come from the
56:00 and we're gonna look at that one . All right. So what this
56:03 is trying to show you here is , look here we are inside of
56:05 membrane. All right. This is mezzanine. All right. And
56:10 it's just kind of a generic uh stage connective tissue that's non distinguishable.
56:17 right. And you can see what I have up here. The little
56:19 stuff represents a bunch of fibers, cells, you can see these are
56:23 non differentiated mesenchymal cells. And what happen is is that one of these
56:28 cells may differentiate into that osteogenic cell then the osteogenic cells begin dividing and
56:33 start producing osteoblasts and what osteoblasts do make bone? And so that's what
56:41 start seeing is you start seeing them down bone in all directions because that's
56:47 what osteoblasts do. I'm just gonna putting it everywhere, right? And
56:51 I'm, I'm basically pushing matrix in directions. And what ends up happening
56:56 you can see I'm starting to put matrix and some of those cells are
56:59 stuck on the inside and when they stuck on the inside, what do
57:01 do they differentiate into osteosis sites and kind of sit there and go
57:06 Is the matrix doing what it's supposed do? And then over time,
57:11 matrix grows and becomes this material called bone. And while woven bone looks
57:17 lot like spongy bone, it doesn't the same strength and blood vessels start
57:22 in and start delivering nutrients and materials that bone as it's growing and then
57:28 that woven bone is growing, it's starting to push the mezzanine away
57:33 where that bone is. And as mezzanine is getting pushed away, it's
57:38 of getting jammed up against itself. so it's getting tighter and tighter and
57:42 on the outside. So the fibers getting tight and the mesenchymal cells are
57:48 tighter together. And now what you're is you're creating that periosteum. All
57:54 . So the periosteum is being formed the inside bone is growing. And
58:00 what happens is, is you end getting with uh on the outer
58:04 That's where you're gonna get those osteocytes sorry, should start with the osteopor
58:09 genic cells, the osteopro genes they'll differentiating, start producing osteoblasts and then
58:15 osteoblasts start lying down compact bone. so does that look like our flat
58:23 we have on the outside periosteum? have that layer of living cells of
58:29 Gits and osteoblasts. Then we have layer of compact, then we have
58:34 the spongy bone. See there are bone and then you go on the
58:38 side, you see the opposites, there's a compact bone, there's the
58:42 osteopro cells and periosteum and then those uh tissues, uh the the fibers
58:48 cells that's gonna form that, that . So that's intramembrane. I start
58:55 a membrane and I grow inside that and I push outward and that's where
59:01 get that flat bone kind of makes . Four simple steps. You guys
59:09 up watching Disney, right? Disney . You remember oso secret agent?
59:16 see III I, I'll find I mean, come on, see
59:22 is it. It's always three simple here. It's four simple steps.
59:29 ? That's all it is. All . But that's not all our
59:33 We've got a bunch of other weird . The other use endochondral ossification and
59:41 early on during life, what ends forming in these membranes are cartilage
59:49 right? And so you can see early on between eight and 12
59:52 you have cartilage like bones that are formed and that's what that first row
59:58 those first s uh set of pictures . And then what ends up happening
60:03 is that, that hyaline cartilage starts replaced. Some of those areas begin
60:09 go through this calcification process. All . And so they basically are dying
60:15 . The cartilage is itself, is away and it's going to be replaced
60:18 bone and it's going to form what called a per osteal collar. And
60:22 you look at the name, what periosteal mean? Ok. Peri around
60:26 . So it's around a bone around . And so here you can see
60:31 my diaphysis. I'm gonna start getting on the outside, that's going to
60:36 the inside of, of materials to , stay alive. So the cartilage
60:41 uh nutrients to keep those cells alive I'm basically depriving them. So they
60:45 dying off and that allows more osteogenic to, to replace there. And
60:50 blood vessels start penetrating in and then re removing all the dead cartilage cells
60:55 I'm replacing them with osteogenic cells. you can see I'm gonna start doing
60:59 to what I did before, which I'm gonna create this uh woven bone
61:03 the outside and then on the outside I have that perio osteo collar.
61:07 also where I have my periosteum. gonna start laying down compact bone.
61:11 you can see here which is forming is the diaphysis and then up here
61:16 the epiphysis, blood vessels are gonna penetrating into that cartilage region and I'm
61:21 start laying down ossification centers again, like what I saw before cartilage is
61:26 to disappear. I'm going to replace with bone and so very early
61:30 what are you made up of predominantly with some bone? I already mentioned
61:36 you, what can kids do, can fall out of trees, they
61:40 bounce downstairs. Why? Because they're , they're made of cartilage, but
61:45 slowly being replaced by bone. And , you can see here, I've
61:48 this region of lots of cartilage even I have regions that are being replaced
61:53 bone. And so here you are little bit older as a child.
61:57 can see there's my pi plate which cartilage. I've got the epiphysis is
62:04 . It's spongy bone on the I've got my um compact bone and
62:08 I have the articular cartilage on the . But what I've done is I'm
62:13 growing in two different directions. I'm up and down and I'm chasing after
62:19 cartilage and the cartilage is laying itself and it's growing towards the epithet.
62:25 I'm just going to use the top an example. So cartilage is growing
62:28 way, pushing the epithet up and got bone chasing it. And so
62:32 is what is allowing the bone to longer. All right, I'm also
62:38 outward. I'm making the bone bigger wider because as I get bigger,
62:44 gonna need something wider to support that . I don't think about how small
62:48 child is. I mean a Some are just, what is that
62:52 year old or four year old? bones are about this big around.
62:56 you want to walk around with bones big around? You know you want
62:59 bones. So you need to grow as well as long and then you
63:05 through puberty and eventually the bone catches and it replaces the cartilage. And
63:10 where you get that epiphyseal plate where basically says there is no more cartilage
63:15 that's when you stop growing. So see it on both ends. So
63:22 did that happen? Well, some than others. So we're gonna just
63:30 these two things very, very All right. So if I'm growing
63:36 the axis of a long bone, is called interstitial bone growth. Interstitial
63:43 inside the bone, right? So am I growing? I've got the
63:47 plate, I got bone here and got bone here. So I am
63:50 in this area. That's why it's . What's happening is um is you're
63:56 see a little bit better right You have up on the top near
64:01 epithelial plate. You have uh an . Well, let me see
64:04 yeah. So you have basically cartilage is already in place. But what
64:08 doing is you are growing cartilage this . So what you're doing is you're
64:13 if this is the uh pith, pushing the pith isis up, you
64:18 this resting cartilage and then you're pushing laying down more and more layers of
64:23 just underneath that. So that's what zone represents. And then as you're
64:29 away from the source of, of , what ends up happening is those
64:35 die. And so they become hypertrophic then they die off and they calcify
64:41 then the bone comes along and no, no, this isn't strong
64:44 . And so it replaces it. so it lays new bone at the
64:48 . So if I'm growing this I'm leaving, I'm adding more and
64:52 bone as I grow upward like does this make sense? The thing
64:57 , is that this process of So here you can see there's the
65:03 , there's the actively dividing. This the bone chasing it. Eventually,
65:08 rate at which the bone is being down becomes faster than the rate at
65:13 the cartilage lays itself down. All . So it's like chasing somebody,
65:19 ? If you're chasing after somebody and faster than them, you're going to
65:22 them. And that's what the bone . The bone is faster than the
65:25 during this period of time and when catches it completely replaces the cartilage.
65:30 there's no cartilage left. It's just and that's why you end up with
65:33 epipens plate. That's all bone. when you stop growing. So that's
65:42 your bones get longer. I tell went from this size, not really
65:46 that size to this size. In of width, we have something similar
65:54 the outside. This is called appositional bone growth on the outside. What
66:01 doing is I am laying down new of bone. So here's my
66:07 here's my osteoblasts. And what I'm is my osteoblasts are laying down new
66:13 . So it's going like this right the outside. So the bones getting
66:19 and thicker and thicker on the outside getting wider and wider and wider and
66:25 . But on the inside, I want all that thick bone because thick
66:30 makes me heavy and heavy means I to do more work. And if
66:34 have to do more work, I to have stronger bones and you see
66:37 becomes a cycle. So what I'm do is I'm going to try to
66:40 the optimum thickness of bone and so the inside at the endosteum, I
66:45 osteoclast breaking down bone. All Now, I am remodeling and going
66:50 the way as, as that's going . So on the outside, I'm
66:52 down more and more bone on the . I'm laying, I'm tearing down
66:56 . So I'm in theory, I'm to be staying the same width,
67:00 that's not what happens. The rate which I lay down bone on the
67:04 is faster than the rate at which break down bone. And so what
67:08 up happening is my bone. If think from the medullary cavity to that
67:12 looks like this over time, it thicker. All right. So when
67:19 young over here, the compact bone not very thick relative to the entire
67:30 . But you can see here, speaking, I have more bone and
67:34 I'm able to support my bigger structure I'm an adult because of that differential
67:40 of growth and breaking down. So bone in a nutshell. So,
67:47 were the things that we covered Well, I'll answer your question
67:51 It's, it's, in theory, supposed to be as close if you
67:55 went and did ratios, you'd see , that the thickness of the bone
68:00 greater. But, but in, what you also notice is that the
68:05 cavity in young people is actually That's the idea. All right.
68:09 I just want to just double So remember you should be asking this
68:13 every day after class. What did learn today? What did you learn
68:15 ? You learned bone shapes, what you learned structure characteristics, cells?
68:25 else? I can barely hear So did we le we learned about
68:29 growth. We learned about the osteoid the osteon, right? And those
68:36 . So I this is not this is not a secret. How
68:41 questions are on the test? How many classes do we have between
68:46 test? 650? Divided by six what come on guys, you should
68:53 able to do that math, Like that eight, it's eight point
68:57 , right? So between eight and . So you're probably gonna get 8
69:02 9 questions from this class, if had to learn different things like the
69:07 , do you think you're gonna question the shape? Yeah. Do you
69:10 you're gonna get a question about the ? Do you think you're gonna get
69:13 question about growth? Yeah. Do see how this is not as difficult
69:20 you might make it out to be you know what you're learning, if
69:23 put it out in front of yourself say, what is the big
69:26 You can work your way down to important details that you need to
69:30 All right, that's all there is it. Just gonna ask you and
69:35 you guys can go, how many types of shapes of bones? Are
69:40 ? One more? Four? I why you think three? Because the
69:44 easy ones, there's the long the flat bone, the short bone
69:48 then there's the, the not sesamoid is the weird one, the
69:54 , but that's it. I this, that's, that's the extent
69:58 difficulty in this class is once you information, everything falls into place.
70:03 right. Don't allow the big words scare you. Take the step
70:08 Ask yourself, what did I learn ? Look at the slides and
70:11 oh yeah, these three slides go , these four slides go together,
70:14 two slides go together and you'll see there are about 6 to 9 maybe
70:20 a big day, 10 ideas that had to walk out with and guess
70:24 , you're gonna be asked a question each one of those ideas. And
70:30 you start doing this in other you'll notice the exact same thing.
70:35 you have a really, really bad , which happens, you guys have
70:40 great
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