Bone + Cartilage 6- Growth


– So there are two ways that we can grow our bone
and cartilage tissue, and if you think
about it makes sense that you would
have a special type or a way, a mechanism
by which growth takes place because we’re dealing
with a solid– a relatively solid tissue.
And so it has– it’s a little bit funky. So, first of all, we can actually have a process
called appositional growth, and this takes place
on the surface. So let’s just make
a little note. This is, like, on the surface. And interstitial growth is,
like in the middle. Now, here’s the deal. Both of these types of growth
occur in cartilage and bone. However, they’re slightly
different. Now, appositional growth
doesn’t make sense. It takes place on the surface. So basically what happens is
at the edge of the tissue near let’s say your
perichondrium or periosteum, basically you are just going to
have cell division take place, and we’re going to end up
with new cells. And those new cells are going to
grow whether it be chondroblasts or osteoblasts, they are going to barf out
more matrix around them, and the bone is going
to increase in diameter, or the cartilage is going
to increase in diameter. So the growth is going
to happen this direction. Can you visualize that? This is increase in diameter. And that happens
through appositional growth. Now, interstitial
growth happens. In cartilage it
makes complete sense. You have a lacuna.
Lacuna. You have a cell
inside the lacuna, and then something triggers,
it’s time to grow. And so the cell will divide
and become two cells. And then the cell
which was an osteocyte; right? Because it was just
chilling in its lacuna. Excuse me.
It’s a chondrocyte because this exact form doesn’t
exactly happen this way in bone. But the chondrocyte is going
to go back and become a chondroblast again. So some kind of chemical
message gets sent when interstitial
growth is going to take place, and now these guys are going to
start barfing out their matrix, and basically they are going
to condense their tissue. Like, they’re going
to squeeze more. They keep their lacuna, but they squish out
more matrix around them. So the matrix becomes
more dense. Does that– you– I mean, I can totally
visualize that. it’s like, if I were in
this room and then I wanted to– and the walls were made
out of clay, and I wanted to, you know,
make more clay, I could totally push more clay
into the walls. And the walls would
become more dense. The clay analogy
isn’t fantastic. Something that squishes down and becomes dense,
like, Wonder Bread. So I’m going to squish more
Wonder Bread onto my walls. And then, like, they started
out being all Wonder Bread-y, but then I could squish more. Like, I could probably fit
an entire loaf of Wonder Bread where I had one piece of Wonder Bread because I
could squish it down. That’s what– your matrix and
cartilage is like that. So your matrix just
becomes more dense. The tissue becomes more
dense with interstitial growth in the cartilage tissue. Interstitial growth
in compact bone. Can you visualize?
Would interstitial growth happen? You can’t make bone
tissue compact-er. You can’t squish it more.
It’s already solid. However, thank you very much, I would like to say interstitial
growth does not happen in bone. Unfortunately, they use the same word for a slightly
different process. They say growth at
an epiphyseal plate, bone growth increased length, at an epiphyseal plate. They call that interstitial.
But think about it for a second. What was the epiphyseal plate? It was hyaline cartilage. That’s not bone. So, sure, the hyaline
cartilage can expand and can create more bone tissue, and we’ll look at that
whole passage in lab today, or whenever you come into lab,
but that is– it’s a different– it’s hyaline cartilage
that’s growing and turning into more bone. However, they refer to it as
interstitial bone growth. Okay.
That’s cool. Do you have any questions
for me? All right.
I think that’s it except for our histology preview
which might have to happen in a second.

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