00:00
So now let's look
at how we form dilute
versus concentrated urine.
00:06
The formation of the
medullary gradient
is going to allow for us
to make concentrated urine,
which is going to
be more concentrated
than our normal blood
osmolality of 300 milliosmoles.
00:22
First when we are over hydrated,
we're going to produce large
volumes of diluted urine.
00:29
This is under hormonal control
where the antidiuretic hormone
production will decrease
this will lead to urine
that is about 100 milliosmoles
or a third of our
blood osmolality.
00:44
Additionally,
if aldosterone is pregnant,
then we're going
to reabsorb ions,
and this is going to create
even more dilute urine.
00:55
When we are dehydrated,
we produce a small volume
of concentrated urine.
01:02
Antidiuretic hormone is released
which will cause us to make
very concentrated urine.
01:09
At maximal antidiuretic
hormone levels
our urine can be as much
as 1200 milliosmoles,
which is the highest
osmolality we find
in our medullary gradient.
01:23
Under conditions of
severe dehydration
about 99% of the
water in our filtrate
will be reabsorbed producing an
extremely concentrated urine.
01:36
So if we take a look
at this diagram,
we see the differences
between over-hydration
and which we are not activating
our antidiuretic hormone
and dehydration
where we're going to
activate the maximum amount
of antidiuretic
hormone that we can.
01:55
With no antidiuretic hormone,
all of the water is able
to be excreted in our urine
and we're going to have
a very dilute urine
but with maximal
antidiuretic hormone,
we're going to insert
as many aquaporins
in the collecting
duct as possible
in order to reabsorb any
water that's in the filtrate
and producing a very
concentrated urine.
02:21
Urea is another substance
that is going to help us form
the medullary gradient
inside the renal medulla.
02:29
Urea is going to
enter the filtrate
in the ascending thin
limb of the nephron loop
by way of facilitated diffusion.
02:39
Cortical collecting duct is
then going to reabsorb water
leaving the urea behind.
02:46
And the Deep medullary region,
we now have a highly
concentrated urea
which leaves the collecting duct
and then enters the interstitial
fluid of the medulla.
02:57
Urea, then moves back into
the ascending thin limb
and we're going to start
the process all over again.
03:04
This is going to contribute
to the high osmolality
found deeper in the
medulla of the kidney.
03:13
Diuretics are going
to be chemicals
that are going to enhance
our urinary output.
03:19
These include things like
antidiuretic hormone inhibitors,
like alcohol,
sodium reabsorption inhibitors,
like caffeine or drugs
that you would take for high
blood pressure or swelling,
Loop Diuretics,
that are going to
inhibit the formation
of the medullary gradient
and osmotic diuretic,
which are substances
that are not reabsorbed
so water will
remain in the urine
and said of being reabsorbed
with the substances.
03:50
For example,
in diabetic patients
high glucose concentrations
will pull water
from the body and has
a diuretic effect.