Full transcript
0:02hi everyone dr. Mike here in this video
0:05we're going to take a look at bony
0:06tissue
0:07so remember bone is just like cartilage
0:10just like blood just like tendons and
0:12ligaments it is another connective
0:14tissue and that means it's going to
0:16contain cells gels and fibers remember
0:19cells gels and fibers make up connective
0:21tissue now the skeleton which is going
0:24to be made up of bones is there to
0:26provide structural support for the body
0:28protection but also is a housing unit
0:30for very important minerals of the body
0:33and we're going to talk about those in a
0:35sec but first let's have a look at the
0:36cells gels and fibers that make up bony
0:38tissue so the cells are bony tissue
0:41include osteo progenitor cells
0:43osteo is a prefix means bone progenitor
0:46means it's going to create something so
0:48these are basically the stem cells of
0:50our bony tissue then we've got
0:52osteoblasts the blast tells you it's
0:55building so these are the bone building
0:56cells they release a substance called
0:58osteoid which helps build bone
1:01osteoclast
1:02think of the class result means crushing
1:04this breaks bone down and the last one
1:07is the osteocytes that's the mature
1:09osteoblasts the mature bone cell now our
1:13bone is constantly been remodeled that
1:15means it's constantly building itself up
1:17breaking itself down building up
1:18breaking down the more you use bone the
1:21more this remodeling process occurs also
1:23the more you use bone the more the
1:25building process occurs to make the bone
1:27stronger now osteoporosis is a disease
1:30in which this remodeling process of
1:33building and breaking is imbalanced and
1:35you have more braking and less building
1:37and you get holes in your bones I'll
1:39talk more about that later on okay so
1:42these are the cell types within bony
1:44tissue what about the gels so the gels
1:47include the glycoproteins and also the
1:51glycosaminoglycans remember they're the
1:52carbohydrates now if we look at bony
1:55tissue 15% of its entire mass is water
2:00okay 15 percent of bony tissue the rest
2:02is what we call dry weight now of that
2:0575 odd 80 percent of that dry weight
2:10what you're going to find is that 30% of
2:12it is going to be
2:13the gel portion so that extracellular
2:16matrix the ground substance what we call
2:18the glycoproteins and the
2:20glycosaminoglycans that's 30% of the
2:22dryer weight the remaining 70% of the
2:25dry weight is actually something that
2:27bony tissue has that other connective
2:29tissues don't have these are the mineral
2:31depositions so 70% of the dry weight of
2:34bone is made up of something called
2:36hydroxyapatite and it's predominantly
2:38calcium and phosphate okay so bone has
2:42all these minerals dissolved into it and
2:44this is what makes bone hard and these
2:47minerals are calcium and phosphate so
2:50that's very very important you'll also
2:52find that we can break up the gels and
2:54fibers together we call the organic
2:57components of bone and the minerals are
3:00the inorganic components of bone so this
3:02is again important as well I'll talk
3:04about that shortly now when it comes to
3:06fibers the major fiber type within bone
3:08is collagen so together the organic
3:11components of bone make up 30% of its
3:14dry weight and the inorganic components
3:16of bone make up 70% of its dry weight
3:19all right now what we're going to do is
3:21look at the anatomy of a long bone so
3:24we've got a long bone here and you can
3:26see that this long bone I've sort of cut
3:29and we're looking inside of that long
3:31bone and you can see that it's made up
3:33of two bone types this is what we call
3:36cortical bone and spongy bone okay
3:41this cortical bone is a very dense bone
3:44this spongy bone by name is a spongy in
3:48appearance looking bone it's not spongy
3:49to feel still very hard but not as hard
3:52as the cortical bone okay so what you're
3:55going to find is you're going to have
3:57the cortical bone sitting on the very
4:00outside of a long bone and then you're
4:03gonna have the spongy bone sitting more
4:05so in the middle of the long bone now
4:08deep within the middle of a long bone is
4:10actually hollow and we call that the
4:12medullary cavity so there is a cavity
4:15deep inside of long bones that's hollow
4:18and it's called the medullary cavity and
4:20what is inside of that hollow area a lot
4:23of our blood vessels but also in the
4:25adult it's going to be
4:27what we call yellow bone marrow okay so
4:31you've got two types of bone marrow
4:32yellow bone marrow that's fat and red
4:35bone marrow which helps us create blood
4:38now in adults the medullary cavity is
4:40yellow bone marrow okay but in an infant
4:44the long bones have red bone marrow so
4:46that means in infants their long bones
4:48are the primary site for red blood cell
4:50production so the question may be
4:52where's our primary site for red blood
4:53cell production now that we're adults
4:55it's predominately in our flat bones so
4:57flat bones are going to be bones of our
4:59skull for example and other sternum and
5:01there are some other places that you'll
5:03find what we call the red bone marrow
5:06now the other thing is that if we were
5:08to take a look at the spongy bone and
5:11the cortical bone a couple of things
5:15firstly would the spongy bone you can
5:16see that there's these holes in them and
5:18you'll find the endosteum
5:20is the most inside portion of a bone the
5:23periosteum is the most external portion
5:25of a bone in the endosteum you're going
5:28to have certain cell types that's these
5:31cell types you're gonna have the
5:32osteoprogenitor cells producing
5:34osteoblasts then you're gonna have
5:36osteoblasts building the bone up so that
5:38means you can build bone from the inside
5:41okay Ostia bus then you have the osteo
5:44class which start to eat and break the
5:46bone up okay when we look down at the
5:49cortical bone which is sitting more on
5:51the outside you'll find that you can
5:53peel away the outside layer of the bone
5:56that's called the periosteum and
5:57underneath that peeled layer you can see
5:59that some of the cells sit so you can
6:02build bone from the outside as well so
6:04from the endosteum you can build bone
6:05from the periosteum you can build bone
6:07for adults most of it happens on the
6:09endosteum
6:10inside the bone you can also see that as
6:13the osteoblasts start releasing all that
6:16substances an actual fact that
6:17osteoblasts they secrete the organic
6:20components they secrete the gels and the
6:21fibers the inorganic components well
6:24that comes from when we ingest foods for
6:26example all right so we've got the
6:28osteoblasts secreting all this osteoid
6:30the gels and fibers and laying it down
6:33and it's like put setting concrete
6:34around it and once it sets concrete
6:37around it it's stuck and once it's stuck
6:38it matures into an osteosarcoma
6:40so you can see the osteocytes sitting
6:42between these layers like the layers of
6:44a tree okay
6:46now another thing that you're going to
6:47find is that bone is highly vascularized
6:50there's a lot of blood vessels cartilage
6:52on the other hand does not have any
6:54blood vessels so there's a big
6:55difference between two connective tissue
6:57types if you look at what we call the
6:59macroscopic anatomy of the long bone
7:01you've got two ends of the bone
7:03they're called the epiphysis okay so you
7:06got the proximal epiphysis that's
7:08closest to the side of attachment and
7:09the distal epiphysis that's farthest
7:12away from the side of attachment then
7:14you've got the long middle portion of
7:16the bone which we call the diathesis and
7:18then in between the diathesis and the
7:21epiphysis we've got the metathesis the
7:23other thing is you can see this green
7:25line that I've drawn here basically
7:28between the metathesis and the epiphysis
7:30that we call the epiphysis line this
7:33epiphany line is all in all of our long
7:35bones as an adult and it's hardened but
7:37it used to be cartilage it's actually
7:39when we grow from an infant to an adult
7:42there's cartilage in here that actually
7:44starts to lay down tissue and then
7:46hardens over time to form bone so to our
7:48growth plates if you break in here as an
7:52infant the growth plate it may stunt or
7:55alter the way that an individual grows
7:57so what we've got here overall is an
8:00outlook or a general outlook or overview
8:03of bony tissue