00:00
Let me just point out
the structure of the optic nerve, in brackets
they are put tract for the reason that I
explained earlier in the lecture. On the
left-hand side, you can see the optic
nerve with a very characteristic central
artery in the middle. And the purple
stain component you see there are all
the axons and they are supporting cells.
00:27
Those axons are projecting from the
ganglion cells in the retina at the
optic disc, which does not have any
photoreceptors in it, so that's our blind spot.
00:38
On the outside of that image that section,
you can see a dense connective
tissue layer. That is the dura, one of the
outer meninges of the brain protecting the
brain and spinal cord. Then you see an
artificial space, a white space and then a
thin line, normally that thin line is up
against the dura and you have a space that
that thin line is the arachnoid layer and
underneath that, that space is real. That is a
subarachnoid space. Ond on the right-hand side,
a higher magnification you then have
the pia directly in contact with the
surface of the ganglion axons
unmyelinated nerve fibres and that is
the pia component and that
actually extends into the bundles of unmyelinated
axon and supports them. So the
optic nerve is surrounded by meninges, not the
epiphery and endomysium, you
find around peripheral nerve which is why I
keep saying it should be called a nerve tract
rather than just a straight peripheral nerve,
so optic tract is a better name for
the structure.
02:03
The supporting cells you can just see little
nuclei and they are going to
be glial cells.