00:01
Here is a diagram explaining the
structure of the renal corpuscle.
00:07
Focus on the yellow colored part of the
renal corpuscle. That really is Bowman's
capsule. It's a capsule wrapping around
another structure I'll describe in a minute.
00:19
That Bowman's capsule has got a very thin
squamous parietal epithelium. And it
then becomes continuous on the left hand
side with the beginnings of the tubule
system, the proximal convoluted tubule.
Bowman's space confined within that
capsule is where the filtrate is going
to go after filtration from the
blood capillaries. Now focus on the
right-hand side of the diagram
and locate an efferent arteriole and
an afferent arteriole. The afferent
arteriole brings blood in and forms a
tuft of capillaries, a very coiled series
of capillaries called the glomerulus. And
blood flows through that glomerulus and
then out through the efferent exiting
arteriole. But during development, those
vessels embedded. They're pushed up
against Bowman's capsule and became encapsulated by
the Bowman's membrane, the Bowman's
epithelium. So we now call that covering
shown here in yellow as the visceral
layer of Bowman's capsule. It's like having
a balloon and you're sticking your fingers
into the balloon. The outer part of the
balloon is the parietal layer of Bowman's
capsule. And the part of the balloon
that's now
around your fingers is the visceral layer.
Now as you see, that visceral layer is very
specialized. The cells aren't squamous. The
cells are called podocytes and they are very
important part of the filtration process.
They're structurally very important for
filtration, and I'll show you details of
that in a moment. Before we leave this diagram,
look across now to the right-hand
side and you'll see a
tubule, a distal tubule. If
you recall from our
diagram when the distal ascending
tubule or segment travels up, it becomes
convoluted. And it becomes convoluted
next to the glomerulus.
02:44
And that's very important because that distal
tubule, that convoluted part of the
distal tubule is in very close approximation
to the afferent arteriole,
and also the efferent arteriole. And that
forms a complex that I'll describe
towards the end of the lecture. It's called
the juxtaglomerular apparatus. So just
remember that area on the diagram that
I've just shown you for later on
when I start describing the details. On
the left-hand side is I repeated that
diagram just to help you recall structures.
On the right-hand side is a
structure of the glomerulus. You can see
Bowman's space and you can see very
flat squamous cells lining the parietal
layer of Bowman's space, and you can see
podocytes that are on the external
surface of the blood capillaries in the
glomerulus. These podocytes are the
visceral layer of Bowman's capsule.
03:56
You can see red blood cells inside the
capillaries. You can see other nuclei
besides the podocytes which
tend to be on the outside.
04:05
Those other nuclei probably belong, or
certainly, belong to endothelial cells, but also
mesangial cells. Embedded in that
glomerulus are cells called mesangial
cells which support the structure of the
glomerulus, support the close association
of the endothelial cells of the
capillaries with the podocytes. But those
mesangial cells are also phagocytic, and
they also tend to regulate the flow of the
blood through these capillaries. Here
now is a diagram explaining the filtration