Full transcript
0:00We're going to be classifying the bones
0:02according to their shape.
0:06We're going to understand the different
0:08functions of the bones.
0:10We're going to define the bone
0:12structures, texture, and markings.
0:16We will discuss the cells of the bone.
0:20We will be describing the chemical
0:22composition of the bone,
0:24bone growth,
0:26the fractures and process processes of
0:29repair.
0:30We going to understand some homeostatic
0:32imbalances related to the bones. And
0:36this includes the bone fractures.
0:41First starting with the skeletal
0:43cartilage. If you remember how many
0:45types of cartilage tissue did we see
0:48when we studied the tissues?
0:51We've got three different types,
0:52exactly.
0:54We've got hyaline cartilage. We've got
0:59fibrocartilage, and we've got
1:02elastic cartilage. If you remember,
1:05the cartilage
1:08is
1:09avascular.
1:12It doesn't contain any blood vessels
1:15or
1:16nerve
1:18fibers. So, no nerves, no
1:22blood vessels in the cartilage. Unlike
1:24the bones, the bone going to have
1:26blood vessels and nerves.
1:32The cartilage is going to be surrounded
1:34by a thick
1:36connective tissue membrane. We call this
1:39is my peri-
1:41chondrium. Peri- peri- means around.
1:44Chondro- means
1:46cartilage. So, the perichondrium is
1:48going to be the membrane that would be
1:51surrounding my cartilage. And this is
1:54where I have got my blood vessels
1:58that would be supplying the cartilage
2:00with the nutrients, with the oxygen for
2:02the cartilage to survive.
2:05So,
2:07cartilage itself is avascular. Like what
2:10type of tissues that we've seen was
2:12avascular? Like the epithelium.
2:15So, remember
2:17two major types of tissues that we have
2:20in the body that are avascular. Those
2:23are epithelium and the cartilage.
2:29You remember
2:31the distribution of the different types
2:34of cartilage. We've got the hyaline
2:36cartilage that was present in the nose,
2:39nasal cartilage.
2:41We've got hyaline cartilage that is
2:43present in
2:47the respiratory tract, including the
2:50larynx,
2:52the trachea rings, the rings of the
2:54trachea.
2:56We've got hyaline cartilage attaching
2:59the ribs to the sternum. Those are what
3:02we call the costal cartilages.
3:06I remember the hyaline cartilage was
3:08covering the articular surfaces
3:12of
3:13the articulating bones in the synovial
3:17joints. So, all the articulating
3:20bones
3:22that they had that had space in between,
3:25a shallow space in between them,
3:28their articular surfaces are covered
3:31with hyaline cartilage.
3:34And as we're going to discuss later on
3:35with the joints,
3:37this will allow the
3:41facilitation of the joint movement.
3:45To cover those articular surfaces with
3:47hyaline cartilage will allow
3:50the facilitation
3:52of the joint movements.
3:55The other type of cartilage that we seen
3:59was the elastic cartilage and if you
4:01remember the elastic cartilage was
4:03located in the ear pinna,
4:06external ear,
4:08and the other location was in my
4:11epiglottis.
4:13And if you remember the epiglottis is a
4:15flexible cartilage that is located above
4:18the larynx.
4:21It's located above the larynx.
4:24And
4:26it it it allows you to prevent the
4:29passage of fluid and food into your
4:31airways. So, when you swallow, what
4:34happens is the larynx is going to be
4:36moving up meeting with the with the
4:38epiglottis that kinks down.
4:41By this, I would be able to close my
4:44airways, preventing the passage of
4:47fluids and food into my airways.
4:52A third type of cartilage was my
4:55fibrocartilage and if you remember,
4:57fibrocartilage did allow you to absorb
5:01compressive shock. So, I did have the
5:03fibrocartilage
5:05in my
5:06intervertebral
5:08discs
5:11as well as in the knee.
5:16Those are the menisci of the knee. Those
5:18are capable to absorb compressive shock.
5:23Another location that we didn't mention
5:25back in the tissues
5:27was the attachment here between those
5:32two pubic bones of the coxal bone. So,
5:36this is called my
5:39pubic bone.
5:44And the pubic bone is one of the three
5:47bones that will form my coxal bone.
5:50The two pubic bones on here are attached
5:53together by fibrocartilage
5:56and this fibrocartilage
5:59attaching the two bones will form a
6:01joint that we call the pubic symphysis
6:04or the symphysis pubis.
6:08So, the joint on here between the two
6:10pubic bones
6:12attached by fibrocartilage
6:14going to be my pubic symphysis.
6:22Moving on to the bones of the skeleton,
6:24we classify the bones into two main
6:26groups
6:28by location.
6:31First, I have the axial skeleton and
6:33this includes
6:35the skull
6:37the vertebrae of the vertebral column
6:41and the thoracic cage.
6:45This is my
6:47axial skeleton.
6:49Appendicular skeleton is going to be
6:51formed by
6:54the bones of both the upper
6:57and lower limbs.
7:01So, again again, we
7:04subdivided
7:05the skeleton into two main groups. We
7:09have the axial skeleton and the
7:12appendicular skeleton.
7:17We classify the bones by shape into
7:21four main groups.
7:23First type
7:26according to the shape is going to be
7:29long bones.
7:31And by definition, long bones are longer
7:35than
7:36they are wide.
7:39So, the length of the bone is greater
7:42than the width of the bone.
7:48Yeah, shoulder blades are part of the
7:50appendicular skeleton.
7:52Shoulder blades
7:54See on here. Shoulder blades are part of
7:57my
7:58appendicular skeleton.
8:01So, if we're looking closer, the bones
8:04of the appendicular skeleton going to
8:06include the clavicle,
8:08the scapula or the shoulder blade, the
8:11humerus,
8:13the bone of the arm,
8:14the two bones of the forearms, those are
8:17my radius and ulna.
8:21The carpal bones, metacarpal bones, and
8:24the phalanges.
8:28Compared to
8:30the lower limb, which is also going to
8:32be part of the appendicular skeleton,
8:34you've got the coxal bone,
8:41the femur, the joint, the bone of the
8:44thigh,
8:48the patella
8:50or the kneecap on here.
8:55The bones of the leg, this includes the
9:00tibia
9:01and
9:02fibula.
9:08And
9:10the tarsal bones,
9:11metatarsal bones, and phalanges.
9:16All those are part of my appendicular
9:18skeleton. The axial skeleton is going to
9:20be
9:22the bones of the skull, including the
9:26facial and cranial bones,
9:30the vertebrae, vertebral column, which
9:32is going to be formed of cervical
9:34vertebrae,
9:36thoracic vertebrae,
9:38lumbar,
9:40the sacrum or the sacrum and the coccyx.
9:46As well as the bones of the thoracic
9:49cage.
9:51This includes the
9:54middle bone of the chest down here. This
9:56is going to be my sternum.
9:58And the ribs that are attached or not to
10:02the sternum.
10:04All right, because we've got some ribs
10:06are attached to the sternum and others
10:08which are not.
10:11So, this is the classification here of
10:13the skeleton again, axial and
10:15appendicular skeletons.
10:18Again, according to the shape, we
10:19classify the bones into four main
10:21groups. First is going to be long bones.
10:25And again, long bones are going to be
10:27longer than they are wide.
10:31Can you excuse me for
10:33for just
10:365 minutes. I have to
10:40go grab something.
10:44All right, I would be back in 5 minutes.
10:47I'm sorry for this.
13:29Mhm.
15:24Mhm.
15:59All right, welcome back. I'm sorry for
16:01this.
16:03All right, so what we're discussing here
16:06is a classification of the bone
16:07according to the shape. Again, we stated
16:10that
16:12the first shape of bones is going to be
16:14the long bones and the bones here are
16:17longer than they are wide.
16:20Second
16:21type of bone according to the shape is
16:23going to be
16:25short bones and short bones by
16:28definition, they are cube-shaped bone or
16:31they are cuboidal. Like
16:34they look like a cube.
16:37Like the carpal bones, for example.
16:42Those are cube-shaped bones.
16:44The tarsal bones.
16:47They are cube-shaped bones.
16:53The patella
16:56here is a cube-shaped bone.
16:58So, those are classified as short
17:03bones.
17:07Examples of long bones you see on here,
17:10like the humerus, for example.
17:13The radius, the ulna.
17:18Femur.
17:19tibia,
17:20fibula. What do you think about the
17:23phalanges?
17:25I asked you, what is the type
17:30according to the shape of the phalanges?
17:33Is this a long bone or a short bone?
17:36What do you think?
17:38It's a long bone. Long bone is longer
17:40than it is wide.
17:42It's longer than it is wide, so it's
17:43still a long bone by definition.
17:45It's not a cube-shaped bone. So,
17:48when we classify the bone whether it's
17:51short or long, we don't
17:53check the length of the bone.
17:56All right. We're looking at something
17:58very specific, which is whether the bone
18:01is longer than it is wide. It's a long
18:03bone, or it's a cube-shaped bone, it's
18:05going to be a short bone.
18:11Flat bones, those are going to be thin,
18:14flat, and slightly curved, and this
18:17includes
18:18the cranial bones, for example. Those
18:21are
18:22flat, slightly curved bones.
18:25Ribs
18:27are going to be considered flat bones.
18:33The
18:34coxal bone on here
18:37going to be considered a flat bone. It's
18:39flat, curved bone.
18:43Sternum,
18:46the scapula,
18:48or the shoulder blade,
18:51all those are going to be
18:53considered flat bones.
18:58So, again and again, if I'm dealing with
19:01a bone that is
19:04thin,
19:05flat,
19:07and slightly curved,
19:11like, for example,
19:12here is the cranial bone.
19:17This is going to be
19:19classified as a flat
19:22bone.
19:28What if I'm dealing with something that
19:30is not longer than it is wide? It's not
19:35cube-shaped bone, so it can't be
19:36considered short,
19:39and it's not
19:41flat bone. It's not thin, flat, and
19:44slightly curved to be considered flat
19:46bone. It has a complicated shape, like,
19:48for example, the vertebrae. As we're
19:51going to discuss, the vertebrae have a
19:54vertebral body, like what you see on
19:56here.
19:58And
20:00on the sides, they have transverse
20:03processes.
20:06And posterior to the vertebral body, I
20:08have
20:09a space called the vertebral
20:13cavity,
20:14on here.
20:16And they have another process
20:19protruding posteriorly. This is going to
20:22be my spinous process. So, you see, I'm
20:25not cube-shaped bone, I'm not a flat
20:27bone, I'm not a long bone. I have a
20:29complicated
20:31shape.
20:32So, we classify those bones as irregular
20:39bones.
20:40So, again, again, according to the shape
20:42of the bone, we classify the bones into
20:44four main groups. Those are
20:47long bones,
20:50short bones,
20:54flat bones,
20:56and irregular bones if they have a
20:59complicated structure, like what you see
21:01on here in the vertebrae. I have
21:03transverse process and spinous process.
21:07I have superior articulating facet,
21:10inferior articulating facet, vertebral
21:13body. I have a hole in here, vertebral
21:16foramen, and so on. So, I have a
21:17complicated structure. I don't have a a
21:20simple structure like the other types
21:23of bones.
21:28Six major functions of the of the
21:31skeleton. First is going to be to
21:33provide support
21:37for the body and for the soft organs.
21:41So, for example, the spinal cord is
21:43going to be uh running down from the
21:45brain.
21:48And it's going to be allowing the nerves
21:52to be
21:54delivering the signals to the effector
21:58organs. So, it needs to be running from
22:04up to down in order
22:08for it to conduct its function. So,
22:10it can be
22:12running like this without having any
22:15kind of support. So, this spinal cord is
22:17going to be supported by the presence of
22:21the vertebrae. That would be surrounding
22:25it.
22:26Like this.
22:31So, I've got in here support.
22:36Another function is going to be
22:38protection.
22:40Like here also, the vertebrae which are
22:43protecting
22:45the spinal cord.
22:47Like the cranial bones which going to be
22:49surrounding the brain to protect the
22:52brain.
22:53Like the thoracic cage which going to be
22:56protecting the heart and lungs. Like the
23:00pelvic
23:02bones which are going to be protecting
23:04the pelvic organs like the urinary
23:06bladder, the uterus, the rectum. All
23:09those are pelvic organs that are
23:11protected by the pelvic bones.
23:18Also, it allows the movement to take
23:21place.
23:24As we going to be discussing in much
23:26more details how the
23:32muscles going to be conducting their
23:35actions.
23:38If I'm drawing here is the shoulder
23:39blade
23:41or the scapula.
23:44You can see it's on here.
23:53And this is going to be the humerus, the
23:55bone of the arm.
24:08And those are the two bones of the
24:10forearm.
24:12radius
24:18and the ulna
24:29I'm drawing now the biceps brachii. We
24:33going to
24:34mention that
24:36the biceps is attached to the scapula at
24:40two points.
24:43Those are the two points to which the
24:45biceps brachii is going to be attached
24:48to.
24:51in the scapula
24:54And it's going to go down to be inserted
24:57in this point on the radius.
25:02What is a muscle contraction? A muscle
25:04contraction is a shortening in the
25:07length of the muscle. So, I have two
25:09attachment of the muscle. If this is my
25:11muscle like this,
25:13it needs to be attached to two points.
25:16One is what we call the origin
25:19of the muscle, and the other point is
25:21going to be the insertion of the muscle.
25:27The muscle contraction is simply the
25:30shortening in the length of the muscle.
25:34And the shortening of the length of the
25:35muscle here is what allows the muscle to
25:38drag
25:40one point to move towards
25:43the other point.
25:45So, in the example here of the biceps
25:48brachii,
25:49what will I be pulling on? I will be
25:51pulling on the radius on here.
25:56So, when I contract my biceps, I'm
25:58pulling the radius
26:00to move towards my scapula.
26:03So, what will I end up with? I would end
26:05up with flexion of the forearm. So, the
26:10forearm is going to be
26:12flexing like this.
26:27Reducing the angle of the joint.
26:29So, try to imagine that I don't have the
26:32radius. Would the biceps be able to
26:35perform its action?
26:37Would it have something to pull on if I
26:39don't have the radius?
26:41If I don't have the radius, would this
26:43biceps be effective? No.
26:47So, without having bones, the muscles
26:50would have no levers
26:53for them to allow the movement. So,
26:59I can't perform movement if I don't have
27:02muscles, but also I don't
27:04I can't perform the movement if I don't
27:07have bones on which the muscles going to
27:09be pulling on.
27:12All right, so I can't perform an action
27:15with
27:16without the muscle being attached to the
27:19bone.
27:21All right, so here skeleton is going to
27:24be performing an important role in terms
27:28of body movement.
27:31Another function for the for the bones
27:34would be storage.
27:36The bones is la are like a bank for
27:41minerals.
27:44And the most important minerals for us
27:47that we store in the bones are going to
27:49be the calcium and the phosphorus.
27:54Why is it so important to have stores of
27:59calcium in the bone?
28:02Because calcium
28:05is essential for vital activities, like
28:09for example,
28:10the blood coagulation.
28:19Like the electrical
28:25conduction
28:30in the cardiac muscle cells.
28:42Normal
28:46electrical
28:47signals
28:51that are traveling
28:52in my nervous system.
28:56So, all those are going to be essential
28:59functions for the calcium.
29:03A disturbance in my blood calcium level,
29:05if I have a decline
29:09in my blood calcium,
29:13what's going to happen as a result?
29:17If I don't have
29:19normal calcium levels, I will fail to
29:22contract my heart.
29:25I will fail to perform a normal
29:28conduction of the electrical
29:30signals in my nervous system.
29:33I will fail to coagulate the blood to
29:36form a blood clot.
29:39So, those are essential and vital
29:42activities that I need in to have normal
29:45blood calcium
29:47levels in order to perform.
29:50So, if I don't have this normal blood
29:52calcium level,
29:55I will end up having
29:57many, many, many problems.
30:00So, what happens
30:02if I don't have enough intake of
30:04calcium?
30:05I would expect to have a drop in my
30:07blood calcium levels, but you don't want
30:10to do this.
30:12So, what your body will do instead is
30:15it will go to your bones
30:20and will ask specific cells
30:24inside your bones, that we're going to
30:26mention in a second,
30:28to break down
30:30the protein of the bone and release the
30:33calcium from your bones to your blood
30:36for you to increase the blood calcium
30:38level back to normal and to be able to
30:41carry on all those activities at a
30:46normal pace.
30:51So, here one of the most important
30:54functions of the skeleton is to act as a
30:58storage site for important minerals like
31:01calcium and phosphorus.
31:05Also,
31:09bones are going to be the site for
31:12hematopoiesis
31:14or the blood cell formation.
31:17And this is going to be taking place in
31:19the bone marrow cavities.
31:24We have two types of bone marrow.
31:28We have the red bone marrow.
31:37And we have the yellow
31:41bone marrow.
31:47Red bone marrow is going to be
31:50distributed
31:52in your flat bones.
31:56It's going to be present in the flat
31:58bones.
32:00And
32:02the proximal
32:05bulging sides of your long bones.
32:13Compared to the yellow bone marrow, it's
32:15going to be present
32:17in the shaft
32:20of your
32:21long bones.
32:24The red bone marrow is going to be
32:26responsible for the blood cell
32:28formation.
32:30This is where
32:32you're going to be
32:33forming
32:36the red blood cells,
32:39white blood cells,
32:42and platelets.
32:44Those are
32:46the blood form elements that circulate
32:49within your blood.
32:53Compared to the yellow bone marrow,
32:54yellow bone marrow is just fat, like the
32:57adipose tissue. It's a stored
33:00fat,
33:02stored energy in the form of
33:03triglycerides
33:06inside your
33:09medullary cavity of the shaft of your
33:12long bones. So, you see on here two
33:15functions
33:16of your bones. First function is going
33:19to be blood cell formation, and again,
33:22this going to be
33:24taken care of
33:26by the red bone marrow,
33:30compared to
33:36Triglycerides are going to be
33:39the storage the storage form of
33:42energy,
33:43and those are going to be located in the
33:46shaft
33:49of long bones,
33:55and this going to be
33:58the yellow
34:01bone marrow.
34:08As we going to see, the bones going to
34:10have
34:12bulges,
34:14depressions,
34:17holes,
34:21and those are going to be either sites
34:25for attachment for muscles, ligaments,
34:27and tendons. So, for example, as we
34:30going to be
34:32studying
34:34in the next chapter.
34:38This is how the tibia going to look
34:40like.
34:55You will see you have
34:58two
35:00concave surfaces.
35:02Those are sites for articulation. They
35:05are joint surfaces.
35:09To which the
35:13convex
35:15parts here of the femur going to be
35:18articulating with.
35:22So, we're looking here at the knee
35:23joint.
35:25So, you have two convex
35:30parts in the femur
35:33and two concave parts
35:35on the tibia.
35:37Again, here we're looking at
35:40the knee joint.
35:51So, those depressed surfaces are
35:56sites for
35:59articulation. They are joint surfaces.
36:03How about those
36:06elevations?
36:07We call those are
36:10forming my intercondylar
36:17eminence.
36:20And the intercondylar eminence here is
36:22that
36:23site of attachment
36:26of two ligaments
36:29that would be attaching the femur to the
36:32tibia. Those are my anterior cruciate
36:34ligament.
36:40And my posterior cruciate ligament.
36:43ACL and PCL. Of course, many of you did
36:46hear about those ligaments.
36:48Did Did anybody hear about those
36:50ligaments before?
36:53ACL, PCL?
36:55Anterior cruciate ligament, posterior
36:57cruciate ligament.
36:59Yeah, those are the ligaments that would
37:00be forming a cross like this.
37:03That's why they are called they are
37:05called cruciate.
37:07One is anterior, one is posterior, and
37:10they are attaching the femur to the
37:12tibia. So, those
37:15eminences
37:17on the bones, they are simply point of
37:20attachment
37:22for the ligaments.
37:24Also, if you see on here, you're going
37:26to see a bulging site
37:29on the anterior surface of the tibia.
37:32This going to be
37:34my tibial
37:36tuberosity.
37:44And the tibial tuberosity
37:46is going to serve as a site of
37:47attachment
37:49for the tendon of a muscle that is
37:52traveling down from the thigh,
37:54which is my quadriceps
38:00femoris.
38:02So, the quadriceps femoris is the large
38:05muscle located in your thigh. It gets
38:08inserted down in here
38:11by the patellar ligament into the tibial
38:14tuberosity. I have this elevation,
38:18this eminence, this bulging part in the
38:21bone because I have a I serve as a site
38:26for attachment.
38:29It might be a conduit for
38:31blood vessels and nerves as we're going
38:33to see for example when we study the
38:35mandible.
38:37This is how the mandible going to look
38:39like.
39:01We'll see
39:03that the mandible has
39:06foramen on the outside. We call this is
39:09the mental foramen.
39:11And a foramen on the inside
39:15of the mandible. This is called the
39:17mandibular foramen. As also serve as
39:20conduit
39:21for nerves to travel, blood vessels to
39:24travel to give the nervous supply
39:27and the blood supply to the bone.
39:32All right. So
39:34So if for example you are performing a
39:36tooth extraction
39:41we'll see that the dentist is going to
39:43be
39:44going all the way
39:47to this point
39:50to give you an injection
39:52that contains the anesthetic for you to
39:55not feel
39:58pain when he is extracting your tooth.
40:02All right. So
40:04here
40:05are serving for conduit for blood
40:09vessels and nerves.
40:14Looking at the texture of the bone.
40:17We have two bone textures. We have the
40:20compact bone, which is
40:24the dense
40:26type of bone.
40:28If we're looking here at the flat bone,
40:30it's a very good example to show you the
40:32difference between compact bone
40:36and the other type of texture, which is
40:38the spongy bone.
40:42So, on here, this is spongy bone.
40:47And
40:49up in here, this is
40:51compact bone.
40:53This compact bone, you see the
40:54difference in terms of texture between
40:57compact bone and spongy bone.
41:00So, compact bone is going to be
41:02dense.
41:03It's going to be usually the outer layer
41:07compared to the spongy bone. It's going
41:09to have a honey comb
41:11shape
41:13of trabeculae that are attached to one
41:17another.
41:19So, I have spaces between the bones. So,
41:22you see on here, this is how they look
41:25like.
41:26Compact bone
41:29and the spongy bone.
41:33Those are the two bone textures that we
41:36are looking at in here. So, in the flat
41:39bones, in the flat bones, what we can
41:42see
41:43we can see
41:46two layers of compact bone.
41:51And in between, you've got spongy bone.
41:55So, this
41:57irregular
42:01trabeculae
42:03on the inside. So, the outer layers,
42:06whether
42:07on the outside or the inside of the
42:09bone, those are compact bone. and in
42:13between we've got spongy bone.
42:19All right, so our first question for the
42:23in-class activities for today,
42:26which one is not a function of the bone?
42:30What do you think?
42:33Do I allow blood cell formation?
42:37Yes or no?
42:38Yes, like what type of bone marrow is
42:41going to be responsible for blood cell
42:44formation? It's my
42:46red bone marrow.
42:49Mineral storage?
42:51Definitely. What am I storing? I'm
42:53storing
42:54calcium and phosphorus. Do I allow
42:57support? Definitely. Do I allow
42:59movement? Of course. I am acting as a
43:03lever for the skeletal muscles to act
43:07on. So, all of
43:09them are functions for
43:13the bone. So, the good answer here is
43:15going to be E.
43:22Moving on to structures of long bone.
43:27The long bone, if you remember by
43:29definition, it's longer than it is wide.
43:35Any long bone going to have
43:40two bulging ends
43:43that are connected to one another
43:46by a
43:48shaft.
44:08I have Z
44:12bulging ends here of the bone.
44:19Those are what we call Z
44:22epiphysis.
44:24Z epiphysis.
44:26So, I have a proximal epiphysis
44:30and the distal
44:33epiphysis. The shaft connecting them
44:35together, this is what we call the
44:38diaphysis.
44:42So, again again, any long bone is going
44:44to be formed of
44:45proximal epiphysis, distal epiphysis,
44:49and connecting them together we've got
44:51the diaphysis.
44:54If we're looking at the internal
44:56structure of the epiphysis, we've got
44:59spongy bone on the inside.
45:06And to the outside of it we have
45:09a layer of compact bone.
45:18And to the outside of the compact bone,
45:21you've got
45:22the
45:23hyaline cartilage covering the articular
45:26surface. So, again again, we're looking
45:28here at
45:30structure of the epiphysis, we've got
45:33internal structure of the epiphysis is
45:37formed of spongy bone.
45:39To the outside of it we've got a layer
45:41of compact bone covered with hyaline
45:44cartilage covering the articular
45:46surface.
45:49Looking closer to the structure of the
45:52shaft or the diaphysis, we can see that
45:56the shaft is going to only be formed of
45:59compact bone.
46:04And to the inside of the compact bone, I
46:06have a cavity. This is what we call the
46:09medullary
46:10medullary cavity.
46:14The outside is going to be covered with
46:17a membrane. We called it the peri-
46:23osteum.
46:27And to the inside, we've got another
46:29membrane lining the medullary cavity.
46:32This is on the inside, so we're going to
46:34call this is my endo-
46:37osteum. Endo- inside, osteum- bone. So,
46:42endosteum is a membrane that is lining
46:44the medullary cavity inside the shaft of
46:48the long bone.
46:50So, again again, what is the structure
46:52of a long bone? We see a proximal
46:55epiphysis,
46:58a
47:00distal epiphysis.
47:02Both are connected together by the shaft
47:06or the diaphysis.
47:12The proximal and distal epiphyses, they
47:14have spongy bone covered with compact
47:18bone.
47:19And most likely those are going to be
47:21articular surfaces, so the articular
47:24part of them are going to be covered
47:27with hyaline cartilage as you see on
47:30here.
47:35On the other hand, my diaphysis, the
47:39diaphysis is going to be formed only by
47:43compact bone. I don't have spongy bone.
47:47And to the inside of the compact bone,
47:49we have the medullary cavity.
47:53And this is where I keep
47:56the yellow bone marrow as you see on
47:58here. As we mentioned earlier,
48:00the yellow bone marrow is going to be
48:03present in the shaft
48:06of the long bone. So, what you see on
48:09here,
48:10inside the medullary cavity, is simply
48:14the yellow bone marrow.
48:20Questions? Questions?
48:31All right. So, looking here at the
48:33membranes that are
48:35going to be present related to the
48:37bones, membranes of the bones, we've got
48:39the membrane on the outside of the bone.
48:42This is called the periosteum.
48:46Peri peri means around.
48:48Periosteum.
48:50And it's going to have a
48:52large number of blood vessels.
48:55Huge number of blood vessels.
48:59And to the inside of the internal
49:03surfaces, covering the internal surfaces
49:05of the bone, we've got
49:08another membrane. We call this is my
49:11endosteum. So, again and again, two
49:14membranes related to the bone, we've got
49:17inside the internal surfaces, we've got
49:21endosteum
49:22covering the outside, we've got the
49:25peri-
49:26osteum.
49:30Moving on to the different types of
49:35osseous
49:36cells or
49:38the bone cells.
49:41First type of bone cells that we are
49:43looking at, it's going to be
49:46the
49:47cell responsible for the formation
49:51of the bone.
49:55So, let's first
49:56think what is the actual bone structure.
50:02It's protein, so it's formed of amino
50:04acids attached to one another. I have
50:07polypeptide chains.
50:09And those polypeptide chains, what is so
50:12special about them is that they are
50:15attached to calcium. So, the calcium
50:21is attaching itself to those polypeptide
50:24chains, to those protein chains.
50:27Which actually will make those proteins
50:30hard. So, think of it
50:33this way.
50:34Your bone
50:36is like
50:38a boiled egg.
50:40The egg is formed of what? It has the
50:43egg white, which is the protein.
50:48So,
50:50it's like those polypeptide chains on
50:52here.
50:55And the egg shell,
50:58this is the calcium.
51:01The boiled egg without its shell, it's
51:05solid, but it's soft.
51:10But with the egg shell on top of it, it
51:13becomes harder.
51:15This is the same exact concept. So, my
51:18bone is actually protein that is
51:20calcified. Without the calcium,
51:24it's going to become softer.
51:30All right, so
51:33what actually going to be forming the
51:34bone is
51:38forming this specific protein
51:43that is responsible
51:46to get attached to the kills.
51:51So when I say bone formation, what I'm
51:53saying here is that those cells have the
51:56ability to produce this type of proteins
52:00that has the ability to become
52:01calcified.
52:08So I've got a cell on here that's going
52:10to be responsible for the production
52:13of this protein.
52:17We call this is my
52:21osteo-
52:24blast.
52:29This is a cell of the bone that is
52:32capable to produce this protein and this
52:35protein on here without the calcium is
52:37called my osteoid.
52:45But where is the osteoblasts are coming
52:48from?
52:49Osteoblasts are coming from
52:52a stem cell.
52:57We call the stem cell
52:59osteogenic
53:04cell.
53:07But this is not highly accurate. So
53:10genesis genesis means to create.
53:14And osteo means bone.
53:17So this is a
53:19cell that would be creating the bone,
53:22but actually it's not the one that
53:24creates the bone. The one that creates
53:26the bone is
53:27the osteoblast.
53:30So a more accurate name for here for
53:33this cell it's going to be osteo-
53:37pro-
53:39genitor.
53:45Osteo bone pro
53:48before proceeds
53:51genitor
53:54the one responsible for the genesis. So,
53:58this is the one responsible for the bone
54:00formation.
54:01What is the genesis?
54:02This is the one that comes before
54:08the genitor.
54:11Or in other words, the stem cell
54:15that will be differentiated into the
54:18bone producing cells.
54:22All right? But for
54:25abbreviation for us
54:29to use the more
54:32simple
54:33name we use
54:36osteogenic cell. This is the most common
54:41name that we going to be using to
54:43describe the cell.
54:45But actually it's not the cell that
54:48produces the bone tissue. It's the cell
54:51that produces the cells that produces
54:54the bone tissue.
54:56It's osteoprogenitor.
54:59It's not the osteogenitor
55:03or osteogenic.
55:05All right? So, osteoprogenitor is the
55:08cell that will differentiate
55:11to form the osteogenic
55:14cell.
55:16Is this clear? Is this clear?
55:27All right, so
55:29those are going to be forming the bones,
55:33the layers of bone. But who going to
55:35actually sit in this bone
55:39is the
55:42mature bone cell. We call this cell is
55:44my
55:45osteal
55:49site.
55:50This cell, the mature cell of the bone,
55:53osteocyte.
55:56The mature bone cells
55:59are the osteocytes.
56:04Another type of bone cells that we're
56:07looking at are the bone-eating cells.
56:16Those are multinucleated
56:18cells. They have a brush border. They
56:20can produce enzymes. And those enzymes
56:23are going to be doing what? Remember
56:25what is the structure of the bone
56:26tissue? It's formed of proteins.
56:31And attached to the protein, you've got
56:33calcium.
56:38Remember when we discussed the lysosomes
56:41in chapter three, we mentioned that one
56:44of the functions of the lysosomes would
56:45be to
56:47break down the bone.
56:49And those are the the actual cells that
56:52contain the hydrolytic enzymes in their
56:55lysosomes to break down, to digest this
56:59protein.
57:00And when I digest this protein, what's
57:03going to happen? I will simply be able
57:05to
57:06move the attached calcium from the bone
57:10to my blood.
57:13We call those cells are my osteo
57:18clasts.
57:21So, again again,
57:23how many bone cells are we looking at
57:26today? We're looking at four different
57:28types.
57:30We've got the osteogenic cell, which is
57:33the stem cell
57:36for the bone production.
57:39We've got the cell responsible for the
57:42formation of the protein that will
57:43become calcified. This is my
57:46osteoblast.
57:49We've got the mature bone cells that
57:51will sit within the bone.
57:54This is my osteocyte.
57:57Site is a cell, so the bone cells, the
57:59mature bone cell is a osteocyte.
58:03And
58:04the last type of bone cells, those are
58:07the cells responsible to break down the
58:10bone matrix.
58:12Those are my osteoclasts.
58:15Osteoclasts.
58:20Looking closer at the structure
58:23of the
58:26compact bone that we've seen
58:29back in chapter four when we studied
58:32the tissues.
58:34If you remember
58:36when we studied
58:37the osseous tissue or the bone tissue,
58:40seen a central canal.
58:43And this central canal was surrounded by
58:48layers
58:50of bone tissue.
58:53And we called those layers are
58:56my
58:58lamellae.
59:03So, the lamellae here are the
59:05weight-bearing
59:09part of the bone. This is the part that
59:11is formed by the calcified protein that
59:15we are discussing in here.
59:22They are forming a column-like
59:25matrix tubes.
59:30Again, those are surrounding a canal. We
59:33call this is the central canal. And
59:37the central canal
59:39is the one that would be carrying the
59:41blood vessels and nerves.
59:48Those lamellae going to have tiny little
59:52spaces
59:55where we going to keep
1:00:00the mature bone cells.
1:00:02Can you remind me what
1:00:04what did we call the mature bone cells?
1:00:12What do we call the mature bone cells?
1:00:20Osteocytes. So, we got those tiny spaces
1:00:24called the lacunae, if you remember.
1:00:27And inside the lacunae, we've got the
1:00:30mature bone cells or my osteo- cytes.
1:00:41So, try to imagine
1:00:43that you are surrounded by concrete from
1:00:45everywhere.
1:00:46Like this cell. This cell is surrounded
1:00:48by calcified protein, like concrete from
1:00:52all around.
1:00:54Would those cells be able to survive if
1:00:56they are surrounded by this calcified
1:00:59protein
1:01:00all around them?
1:01:03No.
1:01:04They won't be able to. So, this
1:01:08raises the need
1:01:10of having
1:01:12tiny canals
1:01:15that would be connecting them to one
1:01:19another.
1:01:20Those are called by
1:01:23canaliculi.
1:01:28And other canals that will be connecting
1:01:31them
1:01:33to the outside and the inside where are
1:01:36you got the blood vessels? Remember on
1:01:38the outside of the bone you've got a
1:01:40membrane that contains blood vessels.
1:01:44We call this membrane is my
1:01:47periosteum.
1:01:51And remember the internal surfaces
1:01:54are going to be aligned by endosteum.
1:01:57And remember
1:01:58where do you got your blood vessels
1:02:01traveling? You got them traveling within
1:02:03your central canal.
1:02:06So you've got
1:02:08canals which are directly connecting you
1:02:16to the outside and inside. So you see on
1:02:19here
1:02:20those canals are
1:02:22the
1:02:25perforating
1:02:31canals.
1:02:34Perforating canals
1:02:36are going to be at right angles to the
1:02:40central canal. They would be connecting
1:02:42the blood vessels and nerves
1:02:44from the periosteum
1:02:47to the central canal
1:02:49of this structure.
1:02:52What do we call this whole structure
1:02:54that we can see?
1:02:57Those building blocks
1:02:59of
1:03:01the compact bone, we call this is an
1:03:05osteon.
1:03:09So the building block
1:03:12you see on here, compact bone is formed
1:03:14of
1:03:15multiple
1:03:19osteons.
1:03:22Each of them
1:03:24going to have a central canal
1:03:26where you've got your blood vessels
1:03:29and nerves.
1:03:32And it's going to be surrounded by
1:03:35layers
1:03:37of weight-bearing protein.
1:03:41Those are the lamellae.
1:03:45And embedded between the lamellae we've
1:03:47got those spaces that contain the mature
1:03:50bone cells. Those are my
1:03:55osteocytes in
1:03:57lacunae.
1:04:00And remember
1:04:01you get canals that will be connecting
1:04:03you
1:04:07to the periosteum. Those are perforating
1:04:12the whole bone, so we're going to call
1:04:14them
1:04:15perforating canals.
1:04:17And we've got those very tiny
1:04:21hair-like
1:04:25canals that will be connecting
1:04:28the
1:04:30osteocytes to one another.
1:04:32We call those are my
1:04:36canaliculi.
1:04:40Canaliculi.
1:04:45Questions? Questions?
1:04:50So again and again, what is
1:04:55the name of the building block of the
1:04:58compact bone?
1:05:00What is the name of
1:05:03of it? It's my osteon.
1:05:07Osteon.
1:05:09All right, so
1:05:11please mark this down, so we've
1:05:13completed just one question so far for
1:05:16the in-class activity, so please
1:05:18name the different parts
1:05:21that would be marked here for you.
1:05:25This is
1:05:27going to be part of your in-class
1:05:29activities for today.
1:07:54And for question number eight, please
1:07:55name
1:07:57the whole structure.
1:08:29All right, so please complete this as
1:08:31part of your in-class activity.
1:08:38Those are
1:08:41I'm sorry, so this is supposed to be
1:08:43number two, not one.
1:08:45Because we've got the first question
1:08:47already.
1:08:48So this is going to be supposed to be
1:08:50number two.
1:08:53All right, so
1:08:55we can have a 10-minutes break. We come
1:08:57back and discuss more about
1:09:00the skeletal
1:09:02system.
1:09:11Now, you see on here, the red part on
1:09:15here, the red part,
1:09:19is the space around the osteocyte.
1:09:27All right, is this Does this make sense?
1:09:31So, the cell is in yellow inside. The
1:09:34red
1:09:35is around it. All right? So, this is the
1:09:38space where the cell is kept.
1:09:44All right, Theodore, did this answer
1:09:45your question?
1:09:49All right.
1:09:51So, we can have a 10-minutes break. We
1:09:53come back, discuss more about the
1:09:55skeleton. Any questions before we move
1:09:57we go for a break?