Glomerular filtration rate is the topic we’re going to go through next.
Glomerular filtration rate is probably the best index
to know how the kidneys are functioning.
A low glomerular filtration rate means that the kidneys are in trouble
and a high glomerular filtration rate is what we would expect
because you need to filter the blood,
which again is one of the primary functions of the kidney.
How do you go about filtering?
The first thing is you need some sort of barrier in between the blood
and what is in the tubule lumen space.
So this glomerular barrier allows this process to happen.
Where is the glomerular barrier?
It’s around the glomerular capillaries.
So let’s orient ourselves a little bit to the blood flow again.
You have the afferent arteriole,
So it’s the barrier around these capillaries that helps prevent some of the fluid leaving.
Now, you want some fluid to go from the capillaries into the lumen space,
or the glomerular space,
but not all of it
so you have a very specialized barrier.
It has 3 primary layers –
a basement membrane,
and an endothelium.
You can see some nice pictures of these both in cartoon and in a micrograph.
So what makes up the glomerular barrier?
Well, the glomerular barrier can be broken down into, again,
three different layers
– the endothelium, the basement layer, and then the epithelium.
This filtration barrier is oftentimes denoted as [K sub f].
In this process, we’re going to use our abbreviation
in some of our equations in the next few slides.
But how does this go through the process from the blood
all the way into the tubule lumen space?
We need to start with what’s lining the blood vessels.
So this is coming from the blood
through little podocytes,
through small little filtration slits,
through the basement membrane here,
and then finally through the epithelium
which has podocytes as these finger-like projections,
as well as some structural proteins as well.