00:00
Hi. Welcome to our video on Diuretics. We're going to give
you an introduction to the kidney to
help you understand how diuretics work. Okay, so first of
all, what do diuretics do? Well, they
increase the kidney's output of urine. Our goal is usually
to lower blood pressure because less
volume means lower blood pressure or decreased edema. So we
use diuretics for patients whose blood
pressure we want to lower and someone we want to reduce
edema. So here's a question for you. What
are 3 main functions of the kidney? No peeking, see if you
can come up with your 3 main functions
of the kidney. Okay, let's see how you did. First of all,
cleaning and maintaining extracellular
fluid is the first function of the kidney we're going to
discuss. Next, acid-base balance. Your
kidney play a really important role in maintaining the
acid-base balance of your body. Third, the
kidneys excrete wastes and substances like drugs and other
things your body needs to get rid
of in order to stay safe. So the 3 main functions of the
kidney: Cleaning and maintaining
extracellular fluid, maintaining acid-base balance and
excreting wastes and substances like
drugs, etc. So here's our next question. What's the
functional unit of the kidney called and how
many are there? So pause for just a minute and put out your
best guess. Okay. The nephron is
the functional unit of the kidney. It's kind of a funny name
but it's an amazing little feature.
01:36
Each kidney has 1 million nephrons. So if you do the math in
your head that's 2 million nephrons
per person. Now these guys are incredible. They stretch from
the cortex to the medulla of the
kidney. So they're all throughout your kidney. Now, the
nephron has 3 main parts and I want to
break those down a little bit. We've talked about the
tubules and you can see those in the drawing.
01:59
The next part is the glumerulus and the Bowman's capsule.
Now I want to talk about how these
fit together. See the glumerulus has it's tangle of
capillaries. Look at the picture there so you
get a good feel for that. It's this tangle of capillaries
and when blood flows into the glumerulus,
the blood pressure forces water and solutes out of the
capillaries and into the lumen of the
Bowman's capsule. So take a look at the picture. You see
that tangle of capillaries, that's what
the blood goes through and then it pushes out water and
solutes into Bowman's capsule and
that starts its way to the process of the nephron because
the water, salt, amino acids, and wastes
that make it into the capsule are collectively called the
filtrate. So when you're reading and
studying when you see that, that's what they're talking
about. Filtrate is filtered from the blood
and into the tubules and that's why we call this stage
filtration. Alright, that may be a little
more than you wanted to know about the nephron but you
cannot believe how incredible these
little units are. So let's go through it one more time.
There's a million nephrons in every kidney.
03:04
The nephrons stretch from the cortex to the medulla and the
nephrons have 3 parts: The tubules,
the glomerulus, and the Bowman's capsule. Now before we go
on, I want to make sure you have that
pretty straight in your mind. So pause for just a minute and
ask yourself a question. What's
the difference between the glomerulus and the Bowman's
capsule? Which one of them contains
a tangle of capillaries? Alright, hopefully you got that one
right that the glomerulus is the tangle
of capillaries and it's surrounded by Bowman's capsule.
Remember when the blood goes through that
glomerulus it pushes out those solutes and the water and it
heads on through the rest of the
nephron. Okay, now look at this graphic. We're going to
layer on the important pieces as we go
through but just think of this as we took a nephron and kind
of stretch it out to make it easier
for you to understand. We start at the glomerulus and you
can follow it around all the way down from
the cortex, the medulla, the Loop of Henle and then back all
the way around to urine excretion.
04:09
So follow that in your handout so you kind of know the route
of what we'll be talking about.
04:13
Now let's lay on those sites that we just talked about.
We've got the PCT, the DCT, the TAL,
the collecting duct and that's where urine is excreted.
That's the first layer. Now let's take a
look at what goes on at these different sites. This to me is
phenomenal, that scientists were
able to understand exactly where this happens. So right up
there you see sodium 65-70%. We're
going to send back to the body about 65-70% of the sodium
right at that site. Next, we can see the
spots here. We have about 25% of the sodium, potassium and
chloride goes back to the body there. The
next site about 5% of sodium and chloride goes back to the
body there and here at the very last stop
on the train 1-5% of sodium, potassium goes back to the body
there. Now why do you care about this?
Because by designing drugs that work at different spots,
these sites of action it determines
how much of a diuretic response your patient is going to
have.
05:17
Carbonic anhydrase inhibitors, those are CAIs. I say that
because it's a mouthful. We lose about 65-70% of the sodium
there. Next up, you've probably
heard of this group, the loop diuretics. Now this is a
pretty potent diuretic that we use for
patients with renal failure or congestive heart failure.
Next up are the thiazide diuretics. Now
look at the difference. You've got the loop diuretics at
that 25% of it getting dumped of. Thiazides
are 5 times less, only about 5% there. So in remembering
which one is a stronger or more potent
diuretic, loop diuretics are going to cause more diuresis
than a thiazide. Last group are the
potassium-sparing diuretics. Now these are the little
fellas, right? They're kind of kind and gentle
but they are at the stop 1-5%. So this is going to cause the
least amount of diuresis. So if I
was going to compare the significance of the fact, the
strength of the fact of the diuretic, loop
diuretics will be the strongest, thiazide is the next
strongest, potassium-sparing have the most
modest or least amount of diuresis. That's why it matters
that you keep in mind where this act.
06:31
They're not specifically down to the pathophysilogical level
but that helps you understand why
we use loop diuretics for people who are really in trouble,
whose kidneys aren't functioning or
in severe failure over something like a potassium-sparing
diuretic.