Full transcript
0:05foreign
0:11okay so now that we've looked at the
0:14gross anatomy of bones with the homatid
0:16hematopoetic tissue and next what we're
0:19going to do is we're going to look at
0:20the external markings that are found on
0:23Bones so bone markings are the bumps and
0:27lumps and divots and things that stick
0:30out on bones that are essentially all of
0:33the external markings and the point of
0:35these external markings are to be able
0:38to give you sites for connections so
0:41like your tendons and your muscles and
0:42your ligaments but they also form little
0:46conduits and divots for blood vessels
0:48and nerves to run through so bone
0:50markings are really really important so
0:52there's a couple terms that we're going
0:54to talk about and there are three major
0:57types of markings that you will find on
1:00the outside of Bones on the external
1:03surface of Bones the first one is going
1:05to be projections
1:07and anytime you see a projection it's
1:09going to be a bulge this is an outward
1:12bulge of a bone so if this were going to
1:14be my epiphysis and my daphyses of my
1:17long bone and that was really bad so
1:19we're gonna try that again
1:21so rather than looking like this if I
1:23have a projection it's going to bump out
1:26that way
1:28you can also have a depression which is
1:31going to be essentially a divot or a
1:34groove-like cut out so if this was my
1:39bone
1:42it would be this guy right here where
1:43it's going to be a depression and this
1:45is where
1:46nerves and blood vessels can pass
1:48through
1:49and then a lot of your rear bones will
1:51actually have openings and these are
1:53going to be holes
1:55and these are going to allow for
1:56passageway
1:57through the bones
1:59so those are the three major types of
2:01bone marking um
2:04that you will find this comes up
2:06primarily when you're going to do lab
2:07and you're doing the naming of all the
2:09bones but here's a short cheat sheet of
2:11all of those okay so all of that was the
2:14gross anatomy of a bone
2:16so the next section is going to be the
2:19microscopic anatomy of bone so we're
2:22going to go a step deeper and then after
2:25the microscopic Anatomy
2:27of bone we're going to look at the
2:29chemical
2:30composition of bone so we're going to go
2:33even deeper so kind of going backwards
2:35down the structural hierarchy so from
2:38gross anatomy to microscopic Anatomy
2:41what this is going to focus on is the
2:44five major
2:46cell types in our bone so there are five
2:52major cell types and they're all going
2:55to be a specialized but they're all
2:57going to start with the same basic cell
2:59type so here's our five types right here
3:02and we're going to break them down
3:05so the first cell type is going to be an
3:08Osteo genic cell so again remember we've
3:12already actually talked about this Osteo
3:14means anything bone genic means
3:17production creation synthesis so this is
3:21going to be a mitotically active stem
3:24cell
3:26so this is the cell that will produce
3:29new bone cells so it is actually going
3:32to be found in quite a few places it is
3:35found in the periosteum
3:38and it's going to be found in the
3:40endosteum so these are the connective
3:42tissues that will cover the inside and
3:44the outside of Bones
3:46so it'll be from the periosteum and the
3:48endosteum of your membranes it's going
3:51to be kind of a flattened
3:53the structure of this will be a
3:55flattened kind of a squamous shape
4:00and the reason we have these osteogenic
4:02cells is that they will then
4:05differentiate which essentially means
4:07become they will become or they will
4:10turn into something else so they will
4:12differentiate into osteoblasts
4:17so your osteogenic cell will
4:20differentiate and become an osteoblast
4:24so that's going to be really really
4:25really important so with this osteogenic
4:28sum becoming osteoblast and it'll just
4:31be a small percent
4:34will stay as osteogenic in order to
4:38produce more new stem cells but in
4:41general an osteogenic cell becomes an
4:44osteoblast so these are a pro janitor
4:47cell so it's going to produce more
4:49remember they're mitotically active here
4:52and they will differentiate into
4:53osteoblast okay so this is really really
4:57important
4:58your next type of cell so we're just
5:01going to draw a little arrow because
5:02your osteogenic cell becomes an
5:04osteoblast
5:06guess what our second type of cell is
5:09an osteoblast so it's going to progress
5:12in this manner
5:13Osteo and remember blast is going to be
5:15anything that is a
5:18immature form of a cell so these are
5:21actually going to be a bone forming cell
5:25so we are producing bone with the cell
5:28and they are going to produce bone
5:31because they are going to secrete The
5:33extracellular Matrix that is so
5:35important in connective tissue so this
5:37osteoblast is going to secrete Matrix
5:40it is also going to be highly highly
5:44actively mitotic so you're going to be
5:46producing a lot of these guys remember
5:48mitotic means it goes through mitosis
5:51which means it has a nucleus which means
5:54it has cell division and it can create
5:56more of itself so osteoblasts are highly
5:59actively mitotic and these are actually
6:02a really really important because they
6:04will secrete
6:07The Matrix that will surround a cell
6:09that is going to be called the osteoid
6:12this is really really really important
6:15right here so with our osteoblast they
6:17are going to secrete The Matrix called
6:20the osteoid and what they're also going
6:22to do with this
6:24is they're going to be mainly
6:25responsible for bone growth
6:27so because they produce the osteoid and
6:30because they are actively mitotic and
6:33osteoblast is responsible for the actual
6:36growth of our bones so that's really
6:39really important when we get to why our
6:42bones do this
6:44so here's an example of a the flat
6:47squamous cell and then our osteoblast
6:50okay so what's interesting is that our
6:53up here I'm going to add one more note
6:55to this
6:56our osteoblasts are going to essentially
6:59be this cell that looks like this and
7:02they're going to secrete this Matrix
7:04outside
7:05and as they secrete this Matrix they
7:07will essentially surround themselves
7:10with it so what will happen with an
7:12osteoblast is an osteoblast will become
7:17an osteocyte
7:21and the reason it will become an
7:23osteocyte is because it will be
7:26completely surrounded
7:29by matrix so essentially this little
7:33cell can produce Matrix and it will
7:37essentially secrete it all the way
7:39around it until the Matrix is covering
7:41the entire outside and hardens and then
7:44that osteoblast can't do anything else
7:46so when it surrounded by a matrix
7:49completely it will then become an
7:51osteocyte that's important because what
7:54is our next type of cell
7:57the next type of cell we're going to
7:59have
8:00is going to be an Osteo site so our
8:04three types of cells so far turn into
8:06the next one
8:08so an osteocyte as a reminder Osteo site
8:12means cell so this is going to be
8:14considered the mature
8:17bone
8:18cell
8:20so when you're talking about a mature
8:21bone cell it's going to be an osteocyte
8:24these are no longer dividing so there is
8:27no more mitosis happening
8:31no division the cell is just what it is
8:33no more reproduction and it's really
8:35going to be responsible for monitoring
8:37and maintaining the Bone's shape it's
8:40going to do a lot of things so it's
8:42going to be really important for just
8:44being the mature structure of a bone
8:47okay unfortunately bone type four and
8:49five do not uh build on a topic on top
8:53of each other
8:54but
8:55we do have two more types of cells so
8:58the next type of cell is going to be
8:59called a bone
9:01lining cell
9:04and a bone lining cell is essentially
9:06going to be just found on the surface of
9:08the bone
9:10it's lining the bone so it's in the name
9:12so bone lining cell is going to be on
9:15the surface and it's going to be where
9:18there is not
9:20remodeling occurring so this is a term
9:23we'll talk about when we get to the
9:24latter half of this chapter
9:26where we're modeling
9:29let me just rephrase that where bone
9:31remodeling is not occurring
9:36this is where you will actually find
9:38these bone lining cells
9:42so this is a flat cell it's going to
9:44help maintain the Matrix and it will
9:47actually line the internal and it will
9:49line external so when it lines the
9:52internal
9:54it will be called a periosteal cell
9:57because that's the periosteum remember
10:01sorry when it lines the external
10:05because the periosteum is the connective
10:07tissue around the outside of the bone
10:08the periosteal cell is found in the
10:11periosteum it will also line the
10:14internal so instead of the periosteal
10:17cell these will be the endosteal cell
10:20because remember the endosteum lines the
10:24inside so if you're trying to remember
10:25about which one is which look at the
10:27name Perry means upon Endo means in
10:32so this is the fourth type of cell that
10:34you need to know and then the fifth type
10:36of cell is a very interesting type of
10:38cell
10:39and this is going to be the osteoclast
10:43so an osteoclast is going to be located
10:46at places along your bone
10:49where you're going to have something
10:51called bone resorption
10:54and so it will be located at areas where
10:57you will have this bone resorption and
11:00that is essentially again going to be a
11:01process we're going to talk about in a
11:03little bit when we talk about bone
11:04remodeling but bone resorption and bone
11:07remodeling are going to be dealing with
11:09healing and producing new and fixing and
11:13growing new bone all of those pieces so
11:15an osteoclast is going to be involved
11:17with that so it's going to be wherever
11:20there is
11:21resorption occurring
11:24so that's really important for these
11:26guys they're essentially going to
11:29be responsible for breaking down any
11:32bone
11:34and then resorbing so think about it
11:36kind of as like a resorption
11:38they're going to reabsorb absorb any
11:42broken down bone
11:46so they're pretty much going to be kind
11:47of a macrophage
11:49that will then clean up bone so that's
11:52the five types of bone cells you can see
11:55the comparison with the last three there
11:57here's an image of an osteoclast I will
11:59not be showing that on an exam so you
12:01don't really need in those
12:02okay so that was the five types of bone
12:05cells but we have two types of bone so
12:07when we're looking at our compact bone
12:11this is the microscopic Anatomy
12:14of our compact bone
12:19so as we're looking at this we're taking
12:22our big long bone and breaking it up
12:25into slices that we can see underneath
12:29the microscope so it is going to consist
12:32of these three parts that we're going to
12:34break down so the biggest part the
12:37overall arching part is going to be the
12:40ostian
12:41you may also see it as a Haversham
12:44system
12:46that's an older name but you still may
12:48come across that so essentially a
12:51haverston system
12:53is going to be made up of something
12:55called an osteon and this is going to be
12:58the structural unit
13:02of compact bone
13:05so compact bone is going to be made up
13:07this is the Lego building block of our
13:09compact bone it's going to be called an
13:11osteon essentially what an osteon is is
13:14it's an elongated
13:17cylinder
13:20that is going to be parallel to the axis
13:24of the bone
13:26so that means if this is my long it
13:30might be epiphyses and my diaphyses
13:32because remember it's a long bone
13:33there's going to be this long slender
13:37cylinder inside that is running along
13:40the same axis of my body it does not go
13:45perpendicular it runs in the same
13:48direction so this long elongated
13:50cylinder
13:51what's cool about this cylinder it was
13:54actually going to be a group of hollow
13:56tubes put together
13:58so if you've ever done a camping cup
14:02where you have put a bunch of these
14:03tubes together essentially here is my
14:06one long tube
14:07and he is going to look like this inside
14:09this other tube it's going to be a straw
14:12inside this straw it's going to be a
14:15toothpick so it's a group of hollow
14:18tubes that are all put together but
14:20they're all going to be essentially
14:22stacked inside of each other
14:26So within each of these group of hollow
14:28tubes these guys are going to be called
14:30La melee so looking at right here to go
14:33back to our osteon it's the structural
14:35unit of bone and it's an elongated
14:37cylinder so what we're now going to talk
14:40about is that it will consist of several
14:42Ling Rings called lamellae so
14:45essentially all of these tubes right
14:47here are called
14:49r lamellae so when you put these
14:52different cylinders together it's going
14:55to be a ring and inside these Rings
14:57these La melee are going to have a
15:00structure that's very cool
15:02they will contain collagen fibers
15:06and these collagen fibers
15:09run in different directions
15:14so they're not all going to be north
15:16south and they're not all going to be
15:18East West so if I have my Hollow tube
15:21right here these collagen fibers
15:24are going to run this way
15:27whereas my next tube has collagen fibers
15:30that are going to run this way you'll
15:32notice they don't run in the same
15:33direction
15:34and then my next one is going to have
15:36collagen fibers that run in the opposite
15:40Direction so they all will have these
15:43lamellae which are going to be these
15:44collagen fibers that are going to run in
15:47different directions and the reason you
15:49have this is because the ability to have
15:51these run in different directions are
15:54going to withstand the ability to twist
15:56this tube so it's really really
15:58important
16:00so you can kind of see that I have drawn
16:02this guy right here so you can see how
16:05that is structured with all of the
16:08different lines going in different
16:09directions okay so that's a single
16:13osteon
16:14if you take that osteon
16:17what you'll actually notice is that if
16:20you take that osteon and you turn it on
16:24its side and you look at it so this is
16:25looking at it on the side but if you do
16:27it straight on what you'll also see is
16:31that it will look like
16:34we'll just do it right here this
16:37so it here's one tube
16:40here's my second tube
16:42here's my third tube so if we take these
16:45guys right here one tube second tube
16:48third tube you are essentially if you
16:50look at it straight on you're going to
16:51see kind of like the hollows of a trunk
16:54or the hollows of a ring so that's
16:56really really cool so this next section
16:59as we're talking about the canals and
17:01coniculi these are going to run through
17:03the core of this osteon so when we're
17:07actually looking at our canals
17:09what we're doing with our these guys are
17:12going to be tubes that are going to
17:14allow things to run through our bone so
17:17there's two types of canals you will
17:19have a central canal
17:23which is going to run through the center
17:28of the osteon
17:32so if I'm looking at it in this
17:34direction
17:36this guy right here is going to be my
17:39central canal
17:40to the middle ring of the trunk
17:45another type of canal you're going to
17:47have is called a Perforating canal
17:51and a Perforating Canal is going to be
17:54at a right
17:56angle
17:58and if it's at a right angle it'll be
18:01the right angle to the axis of the bone
18:05so these Perforating canals are going to
18:08do like this
18:10and go through the axis of the bone
18:16so those are the two different types of
18:18canals you will have
18:21and the goal for both of these is to be
18:23able to have blood fibers and nerve
18:25fibers be able to connect inside and
18:28outside of these bones so Central and
18:31Perforating Haversham is an old name
18:33volkman's is also an old name but this
18:36will run through and this will be at
18:39right angles to the central canal
18:41okay so that's that when you also look
18:44at this on the
18:46um straight down as the cross section
18:48you're going to have a couple other
18:50things so here is my
18:52lovely little
18:56Canal here is my one cylinder of La
19:00melee here is my second cylinder of La
19:03melee here is my third well let me redo
19:07that one
19:08here is my third cylinder of my lamella
19:12so when we're looking at these lamellae
19:15in between there are these little tiny
19:18Hollow sections between each La melee
19:23layer so these are going to be lacunae
19:28so these lacunae are Hollow Junctions
19:35that are going to be found between your
19:39La melee layers
19:41and what's important about these is
19:42they're going to be filled with
19:44osteosites so remember osteocytes are
19:48the mature bone cell that is not
19:50actively dividing
19:52but it is maintaining the structure of
19:54the cell so whenever you have these
19:57lovely little sections right here you
20:00will have your
20:02lacunae right there
20:04okay that's where you will have your
20:06Osteo sites
20:09so the other section that you're going
20:10to have is you're going to have tiny
20:13little canals tiny little tiny tiny tiny
20:18branching little canals these are not
20:20the same as the Perforating canals these
20:22are going to be tiny tiny tiny little
20:24canals so little that they're actually
20:26not going to be called a full Canal they
20:28are called a coniculi which is kind of
20:30like a baby canal and so these are going
20:33to be hair like canals
20:37that are going to connect
20:40lacunae
20:43to each other
20:44so they will connect the lacunae and
20:48they will connect it to
20:51the central canal
20:55so these are not a full Canal they are a
20:58tiny little hair like canal and what's
21:00important about this coniculi is that as
21:02these osteoblasts are again secrete bone
21:05matrix and essentially create a
21:09osteocyte because that's what happens
21:11The Matrix will harden all the way
21:13around the cell and you're going to get
21:15them stuck into this layer that will be
21:17happening so it's a very cool process of
21:21how your osteocytes are produced and
21:24then you have two more things you have
21:26something called an interstitial
21:28um and a circumferential lamella so
21:30lamellae is the layers
21:32so everything that we've drawn so far
21:34has looked like this
21:37layer one
21:39Layer Two
21:40layer three
21:42so these are my three tubes
21:44that are put inside each other
21:46so when we're looking at this
21:48interstitial lamellae
21:51these are all going to be the ones that
21:53are around and make up my osteon but our
21:55osteon are not only one osteon per bone
22:01remember these are the building block
22:02these are the Legos so there's a lot of
22:04osteons put together so I'll have one
22:06osteon there
22:08I'll have one osteon there and then I'll
22:10make a third
22:12osteon
22:14that is here so what you're actually
22:16going to have is this thing called an
22:18interstitial La melee which is going to
22:20fill the gaps between osteons so it will
22:23look like
22:25here's my Austin I'm going to get bigger
22:26oh wait
22:28there's my osteon
22:30now we're going to do this
22:32and we're going to do this and now we're
22:35going to do this and we're going to
22:37connect
22:39so these interstitial lamellae are going
22:42to be this guy right here where they are
22:45not fully around the osteon but they are
22:47essentially creating and connecting the
22:49osteons
22:51and then you also have a different
22:52osteon called a circumferential osteon
22:56and a circumferential osteon so if this
22:58is our microscopic anatomy of our bone
23:00so in order to do this picture we took
23:03our long bone like this and we chopped
23:06it right here and then we looked
23:08straight down
23:10so that's how we got
23:12to this but now if we take our epiphysis
23:16and we do this
23:18as circumferential osteon
23:22is actually going to be where you are
23:24going to have the layers
23:26around the whole thing
23:30so it'll be the width of the actual
23:34um
23:35entire diaphysis so if we come down here
23:39and look these guys real quick this is
23:41the easiest way to describe it
23:43here is the osteon right here
23:47so this is going to be one osteon you'll
23:50notice here is my La melee so here is my
23:54layer one layer two layer three so you
23:59can see that right now with your La
24:01melee but then what you can see is right
24:04here I'm just going to highlight it here
24:05is my osteon here's my osteon you can
24:09see right here
24:11in between all of these guys is where I
24:14will have my circle my inferential
24:17interstitial lamellae but what we're
24:19talking about right now is going to be
24:21our circumferential lamellae which is
24:24these guys so they are going around the
24:27entire width of the diaphysis ship
24:31um shaft so they're going all the way
24:33around the outside so that's what is
24:36happening with the microscopic anatomy
24:38of your compact bone
24:43so
24:44now we're going to switch gears and just
24:46do quickly the microscopic anatomy of
24:49spongy bone
24:51so you'll notice it's not super super
24:53complex and we've already talked a lot
24:55about it so the microscopic anatomy of
24:59spongy bone so as you study for this
25:02class make sure what you're doing is
25:04identifying if the question is asking
25:06about spongy or compact because those
25:08are very different ask about if it's
25:11asking about connective tissue or
25:13skeletal bone look and see are we asking
25:16about gross anatomy microscopic Anatomy
25:20or chemical composition because that's
25:22going to be small medium and large
25:24perspective so the big thing here is
25:26just read the questions to make sure you
25:29understand the specific details that the
25:31question is asking so right now this is
25:34the microscopic anatomy of spongy bone
25:38this is going to look poorly organized
25:40but it's actually going to be not so
25:43spongy bone will have the structure that
25:45we've already talked about which are
25:46going to be the trabeculae
25:49and the trabeculae are going to allow
25:51for the bone to have a very high
25:55strength
25:57and to be strong
25:59so that's really really important within
26:02the US the spongy bone there is no
26:05osteon so this entire process we just
26:07talked about does not exist in a spongy
26:10bone it is only going to be the
26:11trabeculae
26:13so you'll notice right here here's our
26:15layer of
26:17spongy
26:19with our top layer and our bottom layer
26:22of compact and here are our trabeculae
26:27no osteon here
26:29okay so now the last part we're going to
26:31talk about is going to be the chemical
26:33composition of bone so this is the
26:36smallest
26:38um level we're going to talk about when
26:39it comes to the skeletal system chemical
26:41composition of bone
26:45and there's a few important features
26:46here
26:48so chemical composition of bone is going
26:51to be made up of both organic
26:54and
26:57inorganic components so flash back all
27:00the way to chapter two and try and
27:01remember what the organic and the
27:04inorganic components are so when we're
27:06talking about organic components we're
27:08going to start with that
27:11all organic components that make up the
27:15types of bone are going to be first off
27:19all five cell types
27:21because all five cell types have a
27:24plasma membrane have a nucleus
27:28have a mitochondria
27:30have normal operating functional
27:33cellular functions those are going to
27:36require carbon which by definition makes
27:38it organic so all five cell types which
27:42are osteogenic osteoblast osteocytes
27:45osteoclasts and the bone lining cell and
27:48then the osteoid itself so that is going
27:50to be the all five cell types and
27:53the osteoid
27:55the osteoid is going to be made up of
27:57Matrix because this is going to be
28:00highly highly highly make made up of
28:03one-third
28:05of the bone matrix so Matrix is secreted
28:09by the actual cell remember it's a
28:12connective tissue so it has to have that
28:14it has to have the ground substance
28:17to be considered the Matrix and it's got
28:20to have fibers
28:24so flashback to chapter 4 on connective
28:27tissue in order what makes up a
28:29connective tissue so ground substance
28:31and fibers are made up of Matrix and
28:34your osteon will make about a third of
28:36the Matrix so it's really really
28:37important
28:38those are the two primary things about
28:42our chemical
28:44components that are organic in nature so
28:48the reason we have these organic
28:51is because the function of these guys is
28:53they're going to have resilience
28:56and this resilience is going to allow
28:59for
29:00the bone to have its structure
29:04it's also going to allow for the bone to
29:06have its flexibility
29:07so while it is super super strong it
29:11does have the ability to slightly Flex
29:13it is not just a hard structure that
29:16does not have that ability so it has a
29:18slight flexibility to it it's also going
29:20to resist twisting
29:23and these two primary components of the
29:26cell types and the osteon are going to
29:28give the organic components that has
29:31this function for these particular
29:33reasons okay we're going to switch in
29:35that do organic components but you'll
29:38have inorganic so as a reminder
29:40inorganic means that there is not carbon
29:45there is not a carbon molecule in
29:48inorganic components so some of the
29:50inorganic components are going to be
29:52mineral salts
29:54so salts are going to be a large
29:57composition of your bone these are going
29:59to be calcium
30:01phosphate
30:04is it two plus I just can't write it
30:10and phosphate these are salts that are
30:14very very very important in fact they're
30:16so important that they are 65 percent of
30:19bone mass are going to be this calcium
30:21salt so that's really really important
30:23and what this allows for
30:26is this allow for the bone to be super
30:29super hard
30:31so this will allow for the bone to be
30:33able to maintain its structural
30:34integrity and be hard so we're getting
30:37ready to approach Halloween
30:39um as we're approaching Halloween
30:42skeletons are a big decoration the
30:45reason skeletons actually exist is
30:48because the inorganic compounds the
30:51inorganic salts actually are responsible
30:55for the hardness and this is why
30:59the bone will actually last after death
31:03because the rest of your body is made up
31:06of carbon tissues so it's an organic
31:10tissue which will fade and Decay but
31:13your bone is primarily 65 percent in
31:16Organics it's made up of mineral salts
31:19and because it's inorganic it does not
31:22Decay as fast so after death after a
31:25little bit of time all of the organic
31:27components have
31:30um decayed but the inorganic components
31:32or the skeleton is still there so that's
31:35kind of what's happening in that world
31:37and why this is happening so you can see
31:39that here it lasts long after death and
31:42it will cause because of that mineral
31:44composition so that's really cool how
31:46that process all works