00:01
Let us talk further about our
glomerular anatomy, that is relevant
to us clinically. Endothelial cell. So what is
that in the middle
that we're seeing? You see two big circles. Those
two big circles represent what? They represent
glomerular capillaries. Next, what is the lining
of the glomerular capillary? In other words,
what is the lining of blood vessel? Always
endothelial cell. What is beneath that endothelial
cell? You see that dark blue line, the thickened
blue line, that is your glomerular basement
membrane. So in case you missed that picture,
electron microscopy and you won't be able
to make sense of it, maybe perhaps you must
spend a little bit of time with this cartoon
so that you clearly identifies where you are.
By the way what type of imaging study could
you see this in? Light microscopy, electron
microscopy or immunofluorescence? This would
be electron microscopy. So here, you find your
glomerular basement membrane made up of what
type of collagen? Good. Type IV collagen. What kind
of charge? Negative charge. Things we have
already talked about. That endothelial cells
become really important to us because underneath
that endothelial cell if you had a deposit,
you will call it a subendothelial cell. Last
little thing, we will take a look at as we
progressed through here are going to be different
components of this glomerular apparatus.
Endothelial cell, may participate in the production
of glomerular basement membrane. What you
are seeing there, circle in green represents
an endothelial cell. Initial segment of
the filtration barrier, what does filtration
mean to you? You are leaving those circles,
who is? Plasma. In other words, really the
water and the electrolytes and you are filtering
through and then you're moving towards. You see this
aliens? Looks like a one like a cyclops
looks like an eye with feet on top of that circle.
01:57
You are moving towards that. What
is that thing that we're seeing on top of that
circle? Well that would be your visceral epithelial
cell and a.k.a. you know that as being a podocyte.
02:08
Looks like a podocyte. It really looks like
an alien though with a single eye. Imagine
that thing crawling over your glomerular basement
membrane. Let's identify more things.
02:17
Here is the glomerular basement membrane.
Negative charge, collagen type IV. Glomerular
basement membrane, microskeletons of the
glomerulus. You give me a disease in which
the type IV collagen is absent. Good. That
is then called your output, specifically type
IV collagen deficiency. Be careful. As an
important differential of collagen disease,
you also have Ehlers-Danlos and you also have
osteogenesis imperfecta, don't you? So those
are three major collagen deficiency diseases
that you definitely want to know before walking
into your clinical wards or taking your boards.
What were they again? Osteogenesis imperfecta,
deficiency of collagen type I, Ehlers-Danlos,
you have heard of plastic man right. And
you have heard of hyperextensible joints. You have
heard of skin being pulled out to all here
and that is Ehlers Danlos and this is something
in which we see this as being what? Output.
03:16
Glomerular basement membrane is important for
you to know. Collagen type IV. Tram track
we will talk about that as well. It participates
obviously in filtration barrier. There it
is. There is alien that I was referring to
and that your visceral epithelial cell, give
me its proper name that you want to know. A
podocyte. Now, what are those little feet
underneath that podocyte, underneath that
little blob? Those are your foot processes.
03:41
In between the foot processes, what would you have?
Slit diaphragms so that you have proper filtration
of your plasma from the blood vessel, through
your endothelial cell fenestrations, through
the basement membrane and to the side of the
Bowman space. Visceral epithelial cell. What
if you find deposit underneath that epithelial
cell? You call that a subepithelial deposit.
04:05
Prototype, PSGN. Produces glomerular basement
membrane, intercellular junctions are the
final filtration barrier. Once you get passed
this, you are now officially ladies and gentleman
in the Bowman space. One little cell that
I want to make sure that you are clear about, you
see the lining on top there. You see the lining
on top all way outside of your cells. That
is your parietal epithelial cell. And so therefore
if these are proliferating in a condition
are called RPGN, rapidly progressive glomerular
nephritis, you will call that your crescentic
cells. In the middle there is a mesangium,
what does that mean? Think of this as being
your smooth muscle. Why do I keep saying
that? Because at some point in time, if you
glomerular are active, they are going to contract.
Amazing, these things are and in the mesangium,
it may then as we said become thickened and
as you do so, you have deposition of your immune
complexes such as IgA. Give me the two major differentials
that we discussed. Good. IgA vasculopathy,
a.k.a. Henoch-Schonlein purpura and the other
one was IgA nephropathy a.k.a. Berger. Contraction,
produces a matrix, responsible for well, protecting
the entire area. Phagocytic. Mesangial matrix
as what you see deposition of various things
could occur in there. It is the supporting
framework of the structures. The fenestra
represents what? The holes between the endothelial
cell, so you can have filtration taking places.