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0:00
Hello, my name is
Robert Mullins.
I'm a professor
at the University of Iowa.
And I'm going to be speaking
to you today about the choroid.
0:09
Today, we're going to be
discussing several points
about the choroid,
including a general overview
of ocular anatomy
as it pertains to the choroid,
and very briefly we'll discuss
retinal signaling
and photoreceptor cells,
and the fact that that process
requires a large amount
of oxygen consumption,
the source of that oxygen
in the form of
ocular vasculature.
I will then discuss briefly
some of the
physiological insights
into the structure of
the choroidal microvasculature.
We'll spend some time
reviewing the choriocapillaris.
We'll discuss
the groups of cells
that exist in the choroid.
And the development
of the choroid
will be our final point.
0:51
While it is obvious in one sense
that the eye has
an outside and an inside,
the inner-outer axis
is very important
in describing one's
position in the retina.
And so what I've drawn here
is a cartoon of an eyeball
cut in crosssection,
and you can see this line
that denotes
the inner-outer axis.
Taking a small piece
of the yellow retinal tissue
and the brown
choroidal tissue in the cartoon,
we see the layers of the retina
starting from the inside
toward the outside
where the choroid resides.
And these layers
have been, clasically, labeled
based on this
inner-outer access.
So the innermost layer
is the ganglion cell layer,
innermost layer of nuclei.
The next layer of nuclei
is the inner nuclear layer,
and external to that is
the outer nuclear layer.
And the outer nuclear layer
comprises the nuclei
of the photoreceptor cells,
which also have an inner segment
and an outer segment,
again, positioned logically
along this inner-outer axis
as we've discussed.
And external
to the outer segments
of photoreceptor cells,
reside the RPE,
the choriocapillaris,
and the outer choroid.
When light enters the eye,
it passes through the cornea
and the pupil in the lens
and is focused on the retina,
and a photon of light
actually has to penetrate
through all of these
other retinal neurons
before it reaches
the outer segments
of the photoreceptor cells
where the light is converted
into electrochemical signal.
The photoreceptor cells
then signal the bipolar cells
in a mechanism that
we'll very briefly discuss,
the bipolar cells in turn
signal the ganglion cells,
which send an action potential
out through the optic nerve
and to the brain.
