There are four cells in the osseous tissue that I want you to be aware of the first are
going to be osteogenic cells and these are examples of stem cells these are going to
be found in higher densities associated with the outer surfaces of bone and within that
medullary cavity as well and these are going to differentiate into osteoblasts
so there's that term again the -blast so we know that this is going to be important in
terms of that extracellular matrix and that's exactly what we're going to have
the differentiation into these osteoblasts so these are what are actually building the bone
so building that extracellular matrix that will eventually ossify or calcify and create the hard
bone that we're familiar with so you're gonna have these also in higher densities associated
with that outer edge of the bone as well as within that medullary cavity now what
happens with those osteoblasts they're going to secrete the extracellular matrix they're going
to keep surrounding itself with extracellular matrix or secretion and eventually it'll kind
of lock itself in and then you're going to have what's the creation of what's referred to as an
osteocyte and these are the main cells or the mature bone cells so once there's no
more secretion of extracellular matrix that's when you're gonna have the development of these
osteocytes now it's important to note that these cells are not dead so not what we had in terms
of the epidermis with those corneocytes these cells are still doing something they're still
communicating with other osteocytes in order to upkeep the daily metabolism of the bone tissue
and one thing I want you to note with this really nice illustration or all these processes of the
osteocytes and what's going to happen is that these processes are going to communicate with
processes of another osteocytes so being able to actually communicate between cells
and lastly the fourth cell I want you to know are the osteoclast and anytime you have this suffix
of -clast that's going to mean resorption or bone or some type of breakdown and in this case it's
going to be the breakdown of bone tissue now this seems like a bad thing you seem like you wouldn't
want to actually break down the bone but it's actually part of very normal processes in order
to keep the bone tissue strong and healthy you're going to have to break down some of the older
tissue and so that's what this will do it also can have implications if osteoclastic activity
is kind of bumped up so that's the case of what's happening in terms of osteoporosis you're going to
break down bone without having new bone formed by the osteoblasts so a few things I
want you to note here osteoclasts are huge cells so huge in comparison to the other cells that we
just discussed also right in this region right here you have what's referred to as a ruffled
border so this is a very extremely in folded type of plasma membrane and you're from here
you're gonna have secretions of lysosomal enzymes so very high in terms of its acid content in order
to actually break down the bone now one thing I want to note is that the first three cells that
we discuss the osteogenic cells the osteoblasts and the osteocytes are part of the life cycle of
one one type of cell so in osteogenic cell or turn into an osteoblasts that osteoblasts will secrete
that extracellular matrix and keep surrounding itself until it doesn't secrete anymore and once
that occurs then that's referred to as osteocytes so kind of the end of the life cycle in terms of
this is the osteocyte and important in terms of that daily metabolism now this osteoclast is
its own thing it's not part of this life cycle it's actually I'm going to by the creation or
the the coagulation of 50 monocytes or up to 50 monocytes so it's a completely different life
cycle but also just as important in terms of actually breaking down the bone and allowing for
healthy bone to stay so we're gonna those are the four cells I want you to be familiar with now I
want to talk about the two different types of bone so the differences between compact and spongy bone