Full transcript
0:00greetings class today we're going to
0:01start with chapter six which is the
0:03bones and skeletal tissue so if you're
0:06looking for it this powerpoint should be
0:08in your module six just in case you
0:09aren't able to find it so the important
0:12things to take away from this chapter
0:14six are the overall structure of bone
0:17the tiny components that actually make
0:19up the bone and the purpose of bone why
0:21do we have bones so let's go ahead and
0:24start with the three basic types of a
0:27structural tissue called cartilage now
0:30cartilage can actually be a component
0:32for bone building but there are three
0:35separate types of it and we're going to
0:37go through these three separate types
0:38it's very important to remember where
0:41these can be found throughout the body
0:43so the first type that we'll talk about
0:45will be the hyaline cartilage i'm going
0:48to pin out right here so we have hyaline
0:50cartilage this is the most abundant type
0:53of cartilage
0:54so
0:55if it's not elastic it's not fibro it's
0:57going to be high aligned this is going
0:59to be the one that provides a lot of
1:01support flexibility resilience
1:04and these are going to give
1:06our bodies a lot of support
1:09so next up we have elastic cartilage so
1:12this is typically only found in a couple
1:14places of course it is composed of
1:16elastic fibers so think of the ear and
1:20the epiglottis so e for elastic e for
1:24ear e for epiglottis
1:27and then lastly we have fibrocartilage
1:29this is typically found in places that
1:31have a very high amount of stress
1:33applied to them on a daily basis so
1:36think of the knee
1:38the intervertebral discs right those are
1:40the places that are going to be the most
1:42weight bearing so they're going to have
1:44that fibrocartilage
1:48all right let's take a look all right so
1:50you see here
1:52um cartilage of the ear going to be in
1:54green for elastic right so elastic
1:57cartilage is green
1:59and then here you would find the
2:00epiglottis it's not mentioned on this
2:02picture but it is here we go right here
2:04a little tiny flap
2:06that covers the trachea which is the
2:08windpipe whenever we're swallowing
2:10something down the esophagus so that
2:12we're not inhaling those food or drink
2:14particles down into our lungs
2:17um for fibrocartilage this is going to
2:19be our
2:20red all right
2:23so look here so the knee right so think
2:25of maybe the places that have to be
2:27replaced a lot as we get older right so
2:29the knee or things that are kind of
2:31wearing down right so the knee is going
2:32to bear a lot of our weight
2:35we also have a lot in something called
2:38the pubic symphysis if you see right
2:40here and this is where the two pubic
2:41bones the os coxae they bind together
2:44and it's very good to be flexible
2:46especially in women who are
2:48going to have children and of course
2:50then the cartilage in the intervertebral
2:52discs
2:54all right and then everywhere else is
2:56where you're going to find this hyaline
2:58cartilage everything else in blue okay
3:00so whenever you're taking tests it's
3:03always good to remember which things are
3:05not like the others so if you can
3:07remember that you know elastic cartilage
3:09is found in things that start with e
3:11epiglottis and ear the pretty much only
3:14two places that we'll talk about
3:16think of fibrocartilage think of places
3:18that are going to carry a lot of weight
3:21all right and then everything else is
3:22going to be highline
3:24all right so for cartilage it actually
3:27grows in one of two ways there is
3:29something called a positional growth
3:32so with this type of cartilage growth
3:35the new matrix is laid down on the top
3:39of the cartilage
3:40all right but for interstitial growth
3:43this new matrix is made within the
3:46cartilage all right so coming from
3:48within think of interstitial
3:52and then epositional is just the other
3:54one right this is on the surface of that
3:56cartilage
3:57all right let's look at the functions of
4:00bones so there are very seven important
4:02functions that our bones perform for us
4:04on a daily basis they provide support
4:07right
4:07for our body they help us to stand up
4:09straight for our body they also provide
4:11protection for our organs right so think
4:14of our brain
4:16the bone that protects our brain or the
4:18bones would be the skull right so we
4:20have a spinal cord and also our other
4:22vital organs that are surrounded by bony
4:24protection
4:26they help with movement
4:28there are also storage facilities for
4:31mineral and growth factors so things
4:33like calcium and phosphorus and other
4:35growth factors
4:38all right they also help with blood cell
4:40formation this fancy word here is called
4:43hematopoiesis so this occurs in red bone
4:46marrow and it helps to produce all the
4:48cells that are found within the blood so
4:50our white blood cells our red blood
4:52cells and our platelets we also have fat
4:55storage
4:57so this is going to be found more in
4:59those hollow cavities
5:01think more of a yellow marrow
5:03all right and then lastly they actually
5:05produce hormones as well
5:08there is something called osteocalcin
5:11so anytime you see this beginning of
5:13osteo this refers to bone
5:17all right so osteo
5:18so osteocalcin is released by bones to
5:21regulate insulin
5:23glucose
5:24and also help with our metabolism so
5:27really really important functions
5:30so something to remember there are 206
5:33bones in the human skeleton
5:36and they are divided into two main
5:38groups so the middle group is the axial
5:41skeleton
5:43this consists of the skull
5:45the vertebral column and the ribcage
5:48and then the appendicular skeleton so
5:51think of our limbs right so think of
5:53things that are going on the side think
5:55of appendages right appendages
5:58appendicular so let me show you a
6:00picture
6:01if we have it here here we go
6:04so right here in the middle think of
6:06things on the axis how they're turning
6:08on the axis right so right here in the
6:10middle
6:12our axial skeleton our skull
6:15um our vertebral column our ribcage and
6:18then our appendages the appendicular
6:20skeleton so our arms
6:23and legs right
6:27okay so you want to look at that
6:29all right so now we move on to the
6:31different classifications of bones based
6:34on their shape so there are four main
6:36shapes that we classify bones on there
6:38are long bones and of course just like
6:41they sound they are longer than they are
6:43wide so think of your humerus which is a
6:46long bone your femur still think of the
6:48arm and leg bones
6:50next up we have short bones these are
6:53usually more of a cube shaped bone found
6:55in our wrists and ankles they also can
6:57consist of sesamoid bones
7:00so sesamoid bones for instance we have a
7:02patella which is our knee bone if you
7:04want to reach down right here um while
7:06you're listening to this and go ahead
7:08and try to wiggle your knee that little
7:10bone right on the front is the patella
7:13and we also have sesamoid bones within
7:15our thumb
7:17all right flat bones these are thin
7:19usually kind of curved a little bit so
7:21think of your sternum so what the
7:23sternum is also known as the breastplate
7:26right your scapula these are going to be
7:28your shoulder bones your ribs and most
7:31skull bones
7:32and then lastly we have the irregular
7:34bones these are going to have really
7:36special shape so they're really easy to
7:38pick out
7:38so let's take a look back at our little
7:40skeleton
7:42first up we have our long bone this is
7:44called the humerus
7:46we will go over these next week for our
7:49next chapter for chapter seven i do
7:52recommend trying to get down a few of
7:55the bones starting now because it can
7:57get to be a lot right because we do
7:59have hundreds of bones
8:01all right so long bone
8:04uh b we have our irregular bone very
8:06special shape so this is a vertebral or
8:09vertebrae so this is found in the spine
8:12um for c we have a flat bone this is the
8:15sternum
8:18this will be found right here where the
8:19ribs connect and then lastly we have a
8:22short bone so for this one we have a
8:24talus which is one of the bones of the
8:26foot
8:30all right so now let's get a little bit
8:32smaller so let's go ahead and talk about
8:34the two other types of bones so for our
8:37gross anatomy the larger types we can
8:39actually see with the naked eye so we
8:41have compact bone and we have spongy
8:44bone so compact bone is going to be the
8:46hard dense bone and this is usually
8:49going to be the outer layer of every
8:52bone that's going to appear smooth and
8:54solid
8:56within that compact bone we then have
8:58spongy bone and so with the spongy bone
9:02there are a lot of kind of i like to
9:04think of them as maybe railroad tracks
9:06kind of little spikes these are called
9:08trabeculae
9:10and then within the trabeculae you have
9:12a red and yellow bone marrow typically
9:14red marrow is going to be hematopoietic
9:17which means it produces blood cells and
9:20yellow bone marrow is going to be meant
9:22for fat storage
9:24all right let's take a look so we have
9:26our compact bone this is going to the
9:28bone right here in that more of a dense
9:30kind of shiny white right
9:32and then we have spongy bone so think of
9:35a sponge you know right here it looks
9:38porous
9:40it doesn't look like it has a very
9:42regular shape within it
9:44and this is going to be the spongy bone
9:46made up of those little tiny spikes
9:48called trabeculae
9:55all right so the structure of a typical
9:57long bone we'll go through that
9:59so let's go down through our picture to
10:01make it kind of easier for us to
10:03recognize things so here's our humerus
10:05this is the the long bone of the arm so
10:09the shaft of a long bone if you see from
10:11here
10:13to here
10:15this is our diathesis think of maybe
10:17diameter diaphysis is going to be the
10:20long portion or the shaft
10:24of that long bone
10:28okay
10:29um next up there are two epiphyses so we
10:32have a proximal epiphysis so these are
10:35going to be closer
10:38so if it's proximal that means it's
10:39going to be closer to the head
10:41if it's distal it's further away from
10:44the head but these are going to be think
10:46of the end pieces that are more rounded
10:48more irregularly shaped
10:52and then within kind of right here
10:54between the diaphysis and the epiphysis
10:58we have the epiphyseal line or
11:00epiphyseal plate depending on how old
11:02the person is we can also call this the
11:05growth plate
11:09so this is the most active during
11:11puberty and then it closes up about 18
11:14to 21 when most people stop growing
11:18all right if you look within the outer
11:19portion of this bone of course is that
11:21compact bone with our spongy bone if you
11:24notice right here within these epiphyses
11:27and in the diathesis
11:28and then if you look right here in the
11:30middle you'll see a little canal this is
11:32called the medullary cavity
11:36right so you're going to have maybe some
11:38fat storage
11:40some blood cell production and then you
11:42see the bone is supplied by blood
11:45vessels so this is how the bone gets its
11:47oxygen and nutrients
11:49and then you see a little bit of yellow
11:51bone marrow right here
11:56all right so
11:58after we have the different portions of
11:59the bone we also have different
12:01membranes so think of a membrane as
12:03maybe a thin
12:04kind of shear sheet that overlies or is
12:09kind of covering the inside of the bone
12:11so the periosteum
12:14is going to be on the bone surface
12:20and the endosteum is going to be inside
12:24the bone
12:25right here in dostium
12:27it's going to cover the internal bone
12:30surface
12:33all right so let's take a look so
12:35periosteum
12:38and it's actually peeled back for us
12:40right here so you can kind of get a
12:42better look at it
12:44and then the endosteum so think of more
12:45of this as lining
12:48that medullary cavity so peri peri means
12:51around right or to cover why in or in do
12:55means internal or inside of something so
12:58kind of an easier way to remember these
13:01different names um right here we have an
13:03artery taking blood into the bone
13:07all right
13:11all right so we talked about red marrow
13:12so usually this is found in many more
13:15places in newborns
13:18so if something is a red bone marrow
13:20remember this is this is a blood cell
13:23producing something called hematopoiesis
13:26or it can be known as hematopoietic
13:28tissue
13:30so this is found within the trabecular
13:32cavities of spongy bone and the diplo of
13:34flat bones so sometimes the sternum so
13:37in newborns these medullary cavities and
13:40all the spongy bone contain red marrow
13:43but as we age there aren't that many
13:45places that actually contain red marrow
13:49um typically those places are now going
13:51to be located in the heads of the femur
13:54and the femur is the thigh bone
13:56and the humerus so the humerus is the
13:58upper arm bone
14:00all right and these are going to be the
14:01long bones so in case you get a question
14:04like this where are the
14:06the most common places for red bone
14:08marrow to be found in adults it would be
14:11in our long bones so our head of femur
14:13and our
14:14humerus
14:16all right so there are many different
14:18different types of bone markings that we
14:20have that we call them all different
14:22types of names
14:24so let's go over a few but then i'll
14:26leave this table for you guys to go and
14:29go ahead and look over on your own
14:30because i do not want to make it too
14:32long for you all
14:33so let's look at a few so here is
14:36something called a trochanter
14:38if you look right here
14:41um this little little pieces right here
14:46so these are kind of large blunt kind of
14:48a really weird shape
14:50um
14:51and we have them on the femur and that's
14:54really important for different
14:55connections or different attachments of
14:58muscles
14:59so let's look for another good one we
15:01have a tubercle
15:03this is kind of a rounded projection
15:08i don't see one on here all right
15:10we have condyles they're spines and then
15:13processes anything that's a process is
15:15going to be a bony prominent so that
15:17also sticks out so for example on this
15:20vertebrae right here we have a spiny
15:22process
15:26okay
15:27so some other things that are important
15:28we have condyles
15:31these are rounded they're called
15:33articular projections because they do
15:35articulate with other
15:38bones a foramen is a hole kind of a
15:42round or more oval-ish
15:45opening and allows different blood
15:47vessels nerves different things to pass
15:49through all right so let me kind of get
15:50through out of that one
15:52all right so let's go through the five
15:55bone cell types so i would make sure
15:57that i remember these maybe make a
15:58little flash card or just kind of do
16:00some word association so first off we
16:03have osteogenic
16:04cells so these are going to be the stem
16:07cells of the bone these are actively
16:09dividing so they are called mitotic so
16:12if you remember from the earlier
16:14chapters we talked about mitosis right
16:17which is the way that cells divide so
16:19these are mitotic all right so
16:21osteogenic
16:23so maybe think of genesis being created
16:26those things like that all right
16:27remember that osteo refers to bone
16:31osteoblasts our bone building
16:34so these are also mitotic so when i
16:37think of osteoblasts i think of b for
16:40building
16:42all right
16:43um osteocytes are mature bone cells
16:48typically not actively dividing we have
16:51our bone lining cells these help to
16:53maintain the matrix which helps with the
16:55nutrients for the bone um and then we
16:58have osteoclasts so um this refers to
17:01something called bone resorption
17:04so bones are being broken down i like to
17:07think of the c an osteoclast for chewing
17:10so think of bones being chewed up so
17:13they are actually chewed up with
17:14different acids enzymes things like that
17:17so that the calcium can get out of the
17:18bone and typically back into the
17:20bloodstream all right so osteoclasts
17:24c for chewing these chew up bone and
17:26osteoblast b for building these build up
17:30the bone
17:32all right let's take a a few a little
17:34look at the different pictures all right
17:36so first off we have our osteo
17:39progenitor cell this is that stem cell
17:42so some of them can actually become
17:44osteoblasts
17:46which are the bone
17:47building cells responsible for bone
17:50growth of course
17:51all right so we have a couple other
17:54cells so osteoblast and osteocytes so
17:57remember osteocytes
18:00osteo means bone and cyting cell so just
18:02your typical bone cell a mature bone
18:05cell these are from a bone cell lineage
18:09on the other hand osteoclasts remember
18:12those are the chewing these chew up bone
18:15these are from white blood cell lineage
18:18and if you remember anything about white
18:20blood cells you know they are part of
18:23our immune system
18:25and some of those cells especially
18:27macrophages they go in and just engulf
18:30and digest things so kind of similar to
18:33this osteoclast
18:36all right so the next step let's talk
18:37about our compact bone a little bit more
18:40there are quite a few just details so
18:43what i suggest if you're trying to go
18:45ahead and look at these different types
18:47of compact bone to go ahead just sit
18:50down and draw it out and then label the
18:52different portions so what i would
18:54suggest so let me show you a picture
18:58of a osteon a pretty good picture here
19:01we go
19:02so these little circles right here
19:05these are going to be the osteons of the
19:08bone and there are a few different parts
19:11to it okay
19:12so let me show you a better picture
19:21so i can scroll back up here all right
19:24here we go
19:26so
19:26the major components of that compact
19:29bone would be the osteon which is the
19:32structural unit of compact bone we also
19:35have canals and canaliculi then there
19:37are also interstitial and
19:39circumferential lamellae and we'll talk
19:42about all those new words
19:45so the osteons they were known as the
19:47haverzian system but now they are
19:49osteons
19:51it's a cylinder consists of several
19:53rings of bone metrics and these are
19:55called a lamellae so i'm going to show a
19:57little picture
19:58so when they say um
20:01several rings here are several rings and
20:04these rings are called lamale
20:08okay so each ring
20:10these are called lamale while the osteon
20:14is this ring as a whole
20:17okay so just to differentiate between
20:19the two so lamale are the rings
20:27all right so if we look at a osteon from
20:30the side you see we have our lamellae a
20:33little bit easier to pick out right the
20:35different rings that are right here we
20:37also have different collagen fibers to
20:39provide support
20:42and then the things that are going to be
20:44within that central canal
20:46we're going to have an artery with
20:48capillaries and arteries always take
20:51blood away from the heart to the
20:53different tissues of our bodies
20:55we have a vein so think of this blue
20:57structure right here so veins take blood
21:00back to the heart to get re-oxygenated
21:03and then capillaries are exchange
21:05vessels so they help with the exchange
21:07of oxygen and nutrients and then we have
21:10a nerve
21:11so typically
21:13um an artery a vein and a nerve
21:15typically always travel together we call
21:17them the van
21:20so vein artery and nerve and typically
21:22if they travel together they have the
21:24same name or a similar name
21:26not always but a lot of times
21:28all right okay so there's also that
21:31central canal that runs through the core
21:34of that osteon
21:36let me draw my little
21:37osteon again
21:39so these are my lamellae right here
21:42would be the central canal
21:45all right that's going to have the vein
21:47artery and nerves
21:49next up we have these perforating used
21:52to be known as volkman's canals these
21:54canals are lined with endosteum that
21:56occur at right angles to the central
21:59canal so these help with connecting
22:01blood vessels and the nerves of the
22:03periosteum the medullary cavity and the
22:06central canal all together
22:10all right so within these different
22:12canals they have different cavities
22:15little tiny small cavities called
22:17lacunae
22:19and these lacunae contain osteocytes so
22:22those bone cells
22:25radiating out of the lacunae or
22:27something called canaliculi these are
22:29little canals that connect those
22:31individual lacunae and they help with
22:33exchange of nutrients and information
22:39okay
22:40so let's take a look of the structure of
22:42the bone as a whole so these little
22:45circles remember these are our osteons
22:49right the whole thing is the osteon
22:51the little circles are the lamellae
22:54the middle portion right here is the
22:56central canal that has the vein artery
22:59and nerve
23:01and then coming in at a right angle we
23:03have our perforating canal or volkman's
23:06canal and you see how
23:08we have the vein artery and nerve
23:11going down the center and then we have
23:13that right angle and that helps to just
23:16help with the the increased exchange of
23:19oxygen oxygen nutrients and wastes
23:23okay
23:24all right so let's take a little bit
23:25closer look so this is our osteon again
23:28let's look at figure b
23:30so right here you see we have our
23:33central canal kind of just cut off a
23:35little a little slice we have our
23:37canoliculi
23:41okay so kind of hard to see the little
23:43lines that are attaching the osteocytes
23:46in their little beds kind of think of
23:47them like sleeping in there in little
23:49beds called lacunae so the lacunae are
23:52these larger orange portions right here
23:56and the canaliculi are the little lines
23:58that are coming out to interconnect them
24:01okay
24:02all right so i know that's kind of a lot
24:04of stuff but like i said i would
24:05recommend maybe just sitting down if you
24:07like to look at pictures and that helps
24:09you or if you like to draw your own
24:11pictures and actually start to draw out
24:13the different parts of the osteons
24:16all right so let's go on now to spongy
24:19bone we talked about compact bone let's
24:21talk about spongy bone so this actually
24:23allows bones to resist stress
24:27they don't have osteons but they do have
24:29capillaries to help supply nutrients and
24:32they have a lot of those trabeculae
24:34those little train tracks that help to
24:37strengthen that spongy bone so let's
24:39take a look at it so a lot of spongy
24:42bone is found sandwiched between compact
24:45bones so if you kind of take this little
24:46cross section of our skull
24:48we have our compact bone on the outside
24:52and the spongy bone in the middle to
24:54help resist stress so it does look very
24:57unorganized not very neat but it does
24:59have a specific structure and function
25:02in mind to go ahead and provide strength
25:04and flexibility for our bones
25:08so let's look at some of the chemical
25:09composition of bones there are bones
25:12there the bones are made up of organic
25:15components and inorganic components
25:17the organic components are responsible
25:20for bone
25:21resiliency and flexibility
25:25so it's mainly composed of collagen
25:28which is type 1 in bone type 2 and
25:30cartilage and something called
25:31proteoglycans and this is a protein with
25:34a sugar attached
25:37inorganic compound components make up
25:39the majority of bone
25:41a lot of these are made up of something
25:42called hydroxyapatites which are mineral
25:45salts
25:46and this is what allows the bone to have
25:49a nice hard um
25:51be nice and hard and firm and resist
25:54compression all right so organic
25:56compounds help with flexibility
25:58inorganic components help with strength
26:03alright so now let's get to bone
26:04development and this is a process that
26:07is very important to remember
26:09so bone development or production of new
26:12bone is something called ossification
26:16or
26:17osteogenesis
26:20so something to remember is that the
26:21formation of the skeleton or bones
26:24starts in month two of fetal development
26:27you might see it also written as eight
26:29weeks so i do recommend knowing it both
26:31ways i know it seems simple but
26:33sometimes
26:34information is presented in ways you
26:36have not seen before and it can be a
26:38little bit confusing so it begins at
26:40month two of fetal development um
26:42postnatal bone growth does continue on
26:46um until early adulthood and then of
26:48course bone remodeling and repair are
26:51lifelong there are
26:53a couple bones that are pretty much
26:55never fully remodeled and that's going
26:57to be the femur because it is so long
26:58and thick
27:00all right so let's talk about the
27:02different types of bone formation so
27:05remember week eight
27:07we start getting that bonus skeleton
27:10formed from cartilage typically
27:13so we're either going to have
27:14endochondral
27:16ossification or we're going to have
27:19intramembranous
27:20ossification
27:22so endochondral so con or chondro so
27:26that
27:27that prefix
27:30con or chondro
27:34little o right here this is going to
27:36represent cartilage
27:43all right so this is how bone is formed
27:45by being by replacing hyaline cartilage
27:49remember hyaline cartilage is that most
27:52abundant cartilage that we have within
27:54our bodies
27:56so this is actually going to form most
27:58of the skeleton then we have
28:00intramembranous ossification so this is
28:03where bone develops just like it sounds
28:06from a membrane a fibrous membrane
28:10so not a lot of bones are formed from
28:12intramembranous ossification these are
28:15typically going to be the bones that are
28:16above the um above the neck and the
28:20clavicles and then for endochondral
28:22ossification those are going to be most
28:24of the other bones that we find within
28:25the body
28:26all right so our endochondral so all the
28:28bones that are inferior to the base of
28:30the skull except the clavicles
28:33remember we said this begins about month
28:35two
28:36of development it uses that hyaline
28:39cartilage as a model and then is
28:42replaced with bone
28:46so let's now look at the five step
28:48process to endochondral ossification in
28:51a long bone so this is something that
28:52you might see pop up on your test and
28:54quizzes
28:55so first off a bony color forms around
28:59the diaphysis remember that
29:03of the hyaline cartilage model so
29:06everything in blue right here this is
29:08our hyaline cartilage and now you see
29:11the diaphysis or the shaft of this soon
29:13to be long bone you have this kind of
29:15bony collar forming on the outside
29:18alright so step two
29:20the cartilage starts to calcify it
29:22starts to harden in the center of the
29:24diaphysis
29:25and then develops little cavities
29:29okay
29:30um step three the periosteal bud invades
29:33the internal cavities and the spongy
29:35bone starts to form
29:38step four the diaphysis elongates and a
29:41medullary cavity force remember the
29:43medullary cavity is that middle
29:47that middle portion
29:49all right then step five the epiphyses
29:51ossifies they get bones in the epiphyses
29:54that were not there before when
29:56ossification is complete hyaline
29:58cartilage remains only in the epiphyseal
30:00plates and articular cartilage and so
30:04articular
30:06these are typically going to articulate
30:08within their bone and this is what's
30:10going to start um it's going to connect
30:12to the joint eventually
30:16all right so let's talk about
30:18intramembranous ossification it does
30:20have a different process remember these
30:23are going to be the bones of the skull
30:25and of course the clavicles
30:30okay so let's look at these four steps
30:33so step one the ossification centers
30:37develop the fibrous connective tissue
30:39membranes
30:42step two
30:43osteoid is secreted and it also
30:45calcifies so it starts to get hard
30:48then we have excuse me the osteoblasts
30:51continue to secrete osteoid which
30:53calcifies in a few days all right number
30:56four sorry number three immature spongy
30:59bone and periosteum form and then step
31:02four you get compact bone replaces the
31:04immature spongy bone just deep to the
31:07periosteum and the red marrow starts to
31:11develop
31:15alright so let's look at the different
31:17growth in the length of long bones if
31:20you guys want to go ahead and review
31:21this so we have the resting zones the
31:24proliferation zones hypertrophic zone
31:27calcification zone and ossification
31:30zones so knowing where they're found and
31:33that's kind of what's happening right if
31:34something is resting it doesn't really
31:36divide so that's more of the inactive
31:38phases
31:39um proliferation means to grow or to
31:42produce more of right so these are
31:43rapidly dividing so the proliferation
31:46zone is actually the zone that causes
31:49lengthening of the bone
31:51we have the hypertrophic
31:54so hyper means above or more than enough
31:58and then trophic is referring to growth
32:01so these are going to be those older
32:02chondrocytes or those cartilage cells
32:04right that are close to the diathesis
32:07causing kind of a little bump the
32:08calcification zone just like it sounds
32:11the matrix starts to calcify and harden
32:15and then we have the ostification and
32:17osteogenic zones where that collagen is
32:19replaced with bone by those
32:22[Music]
32:23osteoclasts
32:25right here's our picture of the
32:27different zones
32:28let me continue on so i'm not keeping
32:30you guys here too long
32:32so um our growth plate is something
32:35called the epiphyseal plate
32:37and this is typically like i said mostly
32:39open
32:40near
32:41near puberty when it is most active and
32:44this starts to close so for females the
32:48epiphyseal plate starts to just become
32:50inactive or close around 18 and then for
32:53males about 21 years of age there are
32:56also different hormonal controls of bone
32:59growth
33:00growth hormone which we'll cover more
33:04in the second part of anatomy and
33:05physiology
33:06this has its greatest effect on muscle
33:09and skeletons i'm skeletal tissue
33:12we have thyroid hormone testosterone and
33:16estrogens
33:20okay
33:22there are also a few different types of
33:25hormones that we're going to talk about
33:26we'll talk about in a second parathyroid
33:29hormone and something called calcitonin
33:33all right so first let's look up a bone
33:35remodeling and what that actually means
33:37and then we'll apply our different
33:39hormones to them so for a spongy bone
33:42it's pretty much replaced every three to
33:43four weeks so much more often while
33:46compact bone is replaced about every 10
33:49years depending what kind of bone it is
33:50like i said if it's a femur it might not
33:53ever get fully replaced
33:55so bone remodeling occurs with two
33:59different steps it's going to have bone
34:01deposition
34:02and bone resorption so bones being
34:05broken down
34:06so the osteoclast remember those are
34:09bone chewing c for chewing
34:12this is how these cells actually break
34:14down the matrix of bone by secreting
34:17lysosomal enzymes
34:19and something called protons or
34:22hydrogen ions that digest the matrix and
34:25then osteoblasts
34:27remember b for building these are
34:30actually going to actually create more
34:32bone all right so the way that bone
34:35remodeling is controlled is through a
34:37process called negative feedback
34:40that controls the different levels of
34:42blood calcium levels
34:45so calcium is very important it helps
34:48with
34:49muscle function
34:51heart contractions blood coagulation
34:54nerve transmission just so many things
34:55that we need calcium form
34:57a way that we can actually get calcium
34:59to be more fully absorbed in our bodies
35:02is to take it with vitamin d so if you
35:04ever go to the store and you always see
35:06milk plus vitamin d that's because a
35:09vitamin d helps with calcium absorption
35:13bones can also be remodeled in response
35:16to mechanical stress
35:19all right so let's look at some of the
35:20main hormones that help with bone
35:23remodeling we have parathyroid hormone
35:26or pth these come from the parathyroid
35:30glands in the neck these are typically
35:32going to be two on its each side of the
35:34thyroid to the posterior
35:36so what these do they stimulate
35:38osteoclasts
35:40to resorb bone
35:44so these osteoclasts start to trip the
35:46bone and by chewing up the bone they
35:49help to release calcium and that calcium
35:51is able to go into the blood and raise
35:54the calcium levels
35:56all right so once the the optimal level
35:59of calcium has been reached in the blood
36:02then pth stops being produced
36:05all right but on the other hand we have
36:07something called calcitonin and this has
36:10a pretty much the opposite effect of pth
36:13this is produced by c cells of the
36:16thyroid
36:17um in response to high levels of calcium
36:21in the blood so what this does it takes
36:23the calcium out the blood and helps to
36:25build the bone up more by depositing
36:28that calcium into the bone or into our
36:30calcium pools
36:32all right and this picture just shows
36:34that
36:35that um that negative feedback
36:40all right
36:42so let me kind of skip through there are
36:43going to be more things that you should
36:45look at maybe some bone um bone anatomy
36:48and fractures
36:50okay
36:51so let's look at how bones actually heal
36:53it's a four-step process so four stages
36:56so first we get a hematoma which is kind
36:58of a blood bump or think of maybe a
37:00blood tumor
37:02then we get our fibro catalarginous
37:05callus
37:07so fibrocartilage something to remember
37:10is that most scar tissue is called
37:14fibrocartilage we then get a bony callus
37:17and then we have full bone remodeling
37:20all right so now we're going towards the
37:23end of our lecture and we're going to
37:24talk about some of the more clinical
37:26aspects
37:27of bone and the different bone diseases
37:30so there's something called osteomalacia
37:33where bones are poorly mineralized
37:36and this results in soft and weak bones
37:39there's something called ricket so
37:41typically osteomalacia of children
37:44and this is typically coming from a
37:46vitamin d deficiency or insufficient
37:49dietary calcium
37:52all right so
37:53next we have osteoporosis which is
37:55something that you all may have heard
37:57about a little bit more
37:59than the other conditions we just talked
38:01about
38:02it's a group of diseases in which bone
38:04resorption exceeds deposit so that means
38:07the bone is kind of chewed up
38:10more than it is kind of built up by
38:12those osteoblasts
38:15and what happens is that the bone gets
38:17even more spongy so this first picture
38:21is the picture of a normal bone the last
38:23picture is a bone affected by
38:26osteoporosis you see there's much more
38:29holes much more of a spongy appearance
38:32they are not as strong they break much
38:35more easily
38:36all right so one of the main diseases
38:38that are responsible for hip fractures
38:41especially in the elderly
38:44all right so some risk factors for
38:46osteoporosis
38:48they're most often going to be
38:50post-menopausal women
38:53all right so estrogen um plays a
38:56important part in bone density but of
38:59course after menopause that amount of
39:02estrogen drops drastically which can
39:05result in osteoporosis
39:09all right so other risk factors of
39:11course besides just you know naturally
39:14getting older
39:16insufficient exercise so we have to do
39:19weight bearing exercises to make sure
39:21that our bones are nice and thick so as
39:24we age even though we're naturally going
39:26to lose the amount of bone because we
39:28have built up our bones to a certain
39:30degree as we age it's not going to have
39:33such a a serious side effect as
39:36osteoporosis or if you do it won't be as
39:38bad
39:40all right a diet pouring calcium and
39:43protein
39:44uh smoking is always a huge risk factor
39:47for many diseases it could be
39:49genetically linked
39:51let's say if your grandma or an aunt or
39:53even your mother had it it could be
39:55hormone related or taking a lot of
39:58alcohol or other medications
40:01all right lastly how do we treat
40:03osteoporosis so of course with calcium
40:06and it's always going to be calcium plus
40:08vitamin d because that vitamin d is
40:10going to go ahead and reabsorb that
40:12calcium that's coming in through our
40:14food and taking it out to our bones
40:16doing a lot of weight bearing exercises
40:19so going for a walk you know it's a
40:21little bit of weight bearing right maybe
40:23lifting some light weights
40:24um hormone replacement therapy which is
40:27very very common
40:28also known as hrt so once a woman hits
40:31menopause going ahead and getting hrt to
40:34reduce a lot of the side effects of
40:35menopause
40:37it does slow down bone loss but hrt
40:41it has its own side effects such as
40:43causing breast cancer
40:45heart attacks maybe strokes it increases
40:47clots it also causes softening of the
40:51jaw which can cause a lot of jaw
40:53fractures
40:54all right so we have come to the end of
40:56the chapter
40:58chapter six chapter um like i said this
41:01is not comprehensive of the entire
41:03chapter but it is a pretty good review
41:05let me know if you have any questions
41:07have a great day