In this lecture, I am going to talk to you
about cartilage. Cartilage is a very specialized
connective tissue. And when we go through
this lecture, make sure you can understand
the following characteristics of cartilage.
There are three types of cartilage and those
three types of cartilage have differences
structurally. And those differences affect
the function of those cartilages perform in
the body. So you should know those differences
and you should also know about the matrix
components of cartilage. I covered the basic
matrix components in a general lecture on
connective tissue earlier. Cartilage has a
capsule around it called the perichondrium.
And during this lecture, I will explain to
you the role it has in enabling cartilage
to grow, but has limited capacity for allowing
cartilage to repair itself. Finally, we will
go through the process of how cartilage does grow.
When we think about the function of cartilage,
then we need to understand that it is designed
particularly to bear stresses in the body
at joints. But it also forms the skeleton
during our fetal development and that skeleton
is going to be involved with the growth of
bones and I am going to cover the growth of
bones in a later lecture. Cartilage also, in
certain locations, provides components of body
with flexibility and again I will demonstrate
the structural components that allow that flexibility.
So like we should address when we look at
all sorts of tissues, it is very important
that we ask the first question and that is
what are the characteristics of that tissue
or that organ system. So again in this lecture,
let us look at the characteristics of cartilage.
Well, it is avascular. That means it does
not have a direct blood supply. So when you
look at a section of cartilage as you see
here, you do not see blood capillaries, no
arteries and veins. It is avascular.
So later on we need to ponder and answer the question
of how the cartilage cells then get their nutrients.
Cartilage consists like all connective tissues
of cells, fibres and matrix. In the case of
cartilage, the matrix is by far the most abundant
component. It is also the functional component.
It is the main part of cartilage that gives
cartilage its structural characteristics and
its roles in various parts of the body. It
is going to be the component of cartilage
that changes as we look at the three different
types of cartilage that I mentioned earlier on
in the lecture. The cell that lives in cartilage
is called a chondrocyte. It is derived from
mesenchyme, just like all other cells that
give rise to connective tissue cells.
Let us look at the matrix. The matrix is that
clear bluish purply tinge you see in the section.
Have a look also again and identify some of
the chondrocytes sitting in this cartilage
matrix. The extracellular matrix or the matrix
that comprises cartilage is very resilient.
It has those glycoaminoglycans within the
matrix components. And if you recall from my
general lecture on connective tissue, those
glycoaminoglycans hold a lot of water and
therefore the extracellular matrix is very
turgid. It is very strong. It can resist compressive
forces. The collagen that we see in the matrix
of cartilage is type II, generally. But we
will also see that in some cartilages, the
collagen is predominantly type I, very strong
cartilage that requires a very strong collagen
component. And again you do not see little
capillaries or blood vessels in this image
and again I ask you the question think about
how chondrocytes can be nourished.