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0:00
Hello, and welcome back to
The Fundamentals of
Human Physiology.
My name is Jessica Briffa,
and today we'll be going through
the second lecture in the
'Kidney Function' series,
which is on filtration
and clearance.
0:15
The first thing
that comes to mind
on this lecture topic is
what exactly is renal clearance?
Renal clearance is defined as
the rate of urinary excretion of
a substance per unit time,
relative to its
plasma concentration
or in other words, how quickly
a particular substance is
removed from the plasma by
the kidneys and
excreted in urine.
This concept will be
described in more detail in
subsequent slides with examples
of the clearance of
different substances.
0:46
Before we discuss
renal clearance more,
let's consider the
following question
to start to get an idea
about renal clearance.
Why do you think inulin,
which is a type
of dietary fiber,
is the ideal substance for
determining glomerular
filtration rate (GFR)?
For any compound
to be considered
an ideal marker for
determining glomerular
filtration rate,
we must first think back to what
the glomerular
filtration rate is.
Glomerular Filtration Rate
is defined as the volume
of plasma filtered by
the glomerulus over
a specified period.
This in combination
with the fact that
inulin clearance is
measured in the urine,
it means the following must
happen for it to be considered
an ideal substance for
glomerular filtration rate.
It must freely be filtered
by the glomerulus.
It must not be secreted or
reabsorbed in the nephron,
which will change
its concentration in
the urine compared to
the glomerular filtrate.
It must not be synthesized or
metabolized by the kidney,
which will again change
its concentration in the urine
compared to the filtrate.
Lastly, it must be
exogenous such that normal
biological body processes
must not normally
produce a substance.
As you can see, this is a
bit of a trick question as
all of the options are
correct except for option 3.
