Hello, and welcome to this lecture on the
development of the brain, and the influence
that has on the skull. And we’ll also look
at some abnormalities that will develop.
I should advise you that towards the end of
this presentation, there are some photographs
of babies with significant abnormalities,
and this may be something you wish to bear
in mind. So, the plan that we’re going to follow
is that we’ll look at the early development
and flexion of the brain, and then how the
brain regionalizes into different regions,
and then how that influences the development of the
skull. Inevitably, there are some abnormalities
that may arise from things going wrong during
these processes. So we’ll touch in them
towards the end of the lecture. As so often
as the case, we’ll have to go back to the
very beginning to look at the very early stages
of development and the formation of the neural
tube. So in the top image, we have the amniotic
cavity, and below that, we have the yolk sac.
In between the two is the bilaminar disk.
If you’re in the amniotic cavity looking
down, you could see the primitive streak which
establishes the main body axis. Along the
line of this streak, the ectoderm will begin
to roll up on either side to form the
neural tube. And of course, the neural tube will
later become the spinal cord in the adult.
That rolling up process begins round about
the central part of the body axis at this
time. We can see it coming together in the
right-hand diagram, and it will fuse at this
point, and then the line of fusion will extend
towards the head and towards the tail.
So, a little later in the process, we can see
this zipping up process, as it were, moving
towards the head and moving towards the tail.
On either side of the neural tube, which is
derived from ectoderm, as we’ve said, there
are square such structures which are known
as the somites, and these are in the mesoderm.
Later, they will give rise to the vertebrae
among other things. In the right-hand picture,
we can see that the posterior part of the
neural tube has almost completely closed.
But the anterior part towards the head end
is still open. We can also see that this is
enlarged as beginning to form structure, which
will be recognizable in time as the brain.
In this image, a scanning electron micrograph
image of a real human embryo, we can see that
this fusion process is almost completed at
the head and tail end. We can follow this spinal
cord down and mark the somites surrounding
it on each side. Now, let’s look at that process
from the side. We can see the developing