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Changing glomerular filtration rate | Renal system physiology | NCLEX-RN | Khan Academy

Changing glomerular filtration rate | Renal system physiology | NCLEX-RN | Khan Academy


Voiceover: All right, so I
think we have a pretty good appreciation of how we have
some smaller ions, amino acids, glucose and even water
than can leak through these fenestrations and get into
this space right here. Remember, this is just Bowman’s space. They can get into Bowman’s
space where we can then process them into the rest of the nephron. This is Bowman’s space, and we have these podocytes that hug the
arterioles right here by holding on to the endothelial cells. We also have this basement membrane that prevents giant proteins in our red and white blood cells from leaking through. And we have these tubule
cells that help line the other side, and
they’re epithelial cells, they’re in the class of
epithelial cells. Excellent. Now the last thing I
want to cover is what’s happening here from
having an arterial go into a structure and then give
off another arterial. That’s a little weird, right, because we usually like
thinking about arterioles going into capillaries and
then giving out a venule. Well one way to think about
this is sort of like a marathon where there are a
lot of people running on the same street from point A to
point B, and they’re either running in a narrow
street or a wide street. Let’s make a table to think about this. What would happen if we look at our afferent and our efferent arterioles, and we change the diameter of the vessel. What does that do to
the rate of filtration? We’ll write filtration right here. How does the diameter of our vessels change the rate of filtration? If we increase the diameter
of the afferent arterial, or if we have a very wide path
that allows a lot of marathon runners to run into the glomerulus,
that means there’s going to be a lot of blood here
that includes all of the ions, and the amino acids and
glucose, in addition to our blood cells and giant
proteins we talked about. There’s going to be a
lot of stuff over here. So if there’s a lot of
stuff running over these fenestrations you’re going
to have a lot of leakage, and so there’s going to
be a lot of filtration. More filtration occurs if there are more people or more marathon
runners running into this space right here, so more filtration. What about if we did that
with the efferent arteriole? Let’s say we increase the
diameter of the efferent arteriole so there’s space
for more marathon runners to run away from this very narrow street, or this place where a lot
of people can run off the pavement and get into these
holes and go elsewhere. If we increase the diameter
of our efferent arterial and allow people to leave,
they’re not going to be able to stay around here
for a long period of time, they’re not going to be
near these fenestrations. That means that our filtration rate will decrease, because the blood is moving away from the place that it would be filtered. The same thing goes if we decrease the diameter of our afferent arteriole. If we decrease the amount
of runners or blood that can come into the glomerulus,
that means there’s going to be less fluid filtered out,
so a lower filtration rate. This is actually what happens
with renal artery stenosis. If we have a very narrow
or stenosed vessel – that’s what stenosis
means, it’s just narrow – renal artery, that means
there’s going to be less blood that branches off and goes
to our afferent arteriole. There’s going to be less
blood that runs across our fenestrations and is filtered away. On the flip side, if we
decrease the diameter of our efferent arterial that makes
it difficult for our runners to leave this fenestrated
vessel, so there’s going to be some backup, there’s going
to be a lot of ions and amino acids and glucose hanging
around here near these holes. If blood backs up that
means so do these guys, so then they’re going to be
filtered through these holes and collected into Bowman’s
space, so our filtration rate will increase, it will
increase because there’s a lot of backup that allows
more time for filtration. Maybe if you’re interested in
learning about kidney diseases later on there’s a lot of
stuff that tweaks this system, that messes around with
the afferent arterial or the efferent arterial,
sort of like what I talked about for renal artery stenosis. I encourage you to think
about what can go wrong with this process and
how things can change, that’s kind of the best
way to learn about it. That’s how our glomerulus works. Let’s move on to the
next part of our nephron.

19 thoughts on “Changing glomerular filtration rate | Renal system physiology | NCLEX-RN | Khan Academy

  1. Oh yeah my friend, really interesting in the renal diseases. Especially akd and ckd and how it's progressed into esrd. Much appreciated.

  2. This was AWESOME!  I've read my text, gone to lecture, met in groups, etc.  But, this is the first time I really understood what happens when afferent and efferent arterioles dilate/constrict.  Thanks!

  3. thanks so much. This actually helped me to understand well the whole thing rather than reading my lecture notes.

  4. So a larger diameter in the afferent arteriole increases filtration rate and a smaller diameter in efferent arteriole increases filtration rate.

  5. Dude, you explain GFR better than my lecturer and in 4 minutes nonetheless. thanks for the video man, its been incredibly helpful

  6. If that's the case then why does renin causes vasoconstriction in efferent arterioles when it wants to increase the Arterial pressure

  7. How does the basement membrane prevent big molecules from passing through into the epithelial cells? And how do they not just get stuck in the basement membrane ?
    Thanks for the video – phenomenal stuff..God bless

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