I am going to describe bone formation and
growth in this lecture. As I pointed out in
another lecture in this histology course,
there are number of very important functions
of bone does and I will repeat them here because
when we talk about bone growth and bone formation,
the idea is to create bone in the adult can
support these different functions such as
protecting the heart, lungs and brain, vital
organs, forming the skeleton and allowing us
to move, supporting the body and body weight.
It's also a mineral reserve and I will
explain that towards the end of this lecture.
It's a reservoir for calcium and phosphate.
And I have also given a lecture on bone
marrow in this lecture series, in this histology
course and there I described the importance
of bone marrow and how it is housed within
spongy bone and also the medullary components
of young bones. At the end of this lecture,
I would like you to be able to understand
the processes of firstly bone formation, but
then the difference between intramembranous
ossification and endochondral ossification.
I will briefly describe how bone is mineralized
to become a very hard structure and then also
describe the structure of a synovial joint.
So it is important that you understand each
of these topics that I have listed on the
left-hand side here. On the right hand side,
you can see the head of the femur that is
going to articulate with the hip bone. And
I am going to describe just as an introduction
to this lecture, some of the major components
of a long bone, of a bone that makes up an
axial skeleton, a bone that makes us move
by the action of skeletal muscles on it. There
are different sorts of bones that I will
summarize here. First of all, you can classify
bone as being very compact, such as the very
firm bone that it is labelled there, on the
very edge of this femur, and also it can be
spongy or cancellous bone as you see labelled
here as well. The spongy and cancellous bone
tends to be up towards the epithelial areas
of each long bones and that is the area where
the bone marrow can be housed as well as in
the medullary cavity, which is a central empty
space along the diaphysis of a long bone.
There are long bones, short bones, flat bones
and irregular bones in the body. Think about
the bones in our wrist, fingers, the long
bone such as the femur one that I have described
here, irregular bones again in our wrist joints
and in our finger joints, flat bones in our
skull, the cranium. So there are different
sorts of bones just based on their shape and
size as well as being either compact or spongy.
In this lecture, I am going to emphasize the
diaphysis, the long part of the long bone
and also the epiphysis you saw in the previous
slide a section cut through the longitudinal
axis of these long bones. And I showed you
the spongy bone and then in the epiphysial
region and also the very compact bone and
the medullary cavity that creates the central
empty space in the diaphysis of the long bone.
And I want you to have a visual image of this
bone and take this image through this lecture
because what we are going to do in this lecture
is go through some of the general simpler
processes whereby this long bone develops
during fetal life from a cartilage model or a
cartilage template. And that is called endochondral
ossification. I am going to briefly mention
the formation of flat bones such as the bones
in the cranium. They develop from a membrane
of mesenchyme. No cartilage template precedes
the formation of this bone. Therefore, it
is called intramembranous ossification.
Development of bone or formation of bone
purely from a membrane of mesenchyme.