I'm going to draw for you two
of the most important organs in our body. And actually, on the left
and right side of our body, they pretty much look like
that, like little kidney beans. And in fact, that's
what they are. They're kidneys. And so we have some
arteries, the renal arteries that flow into them. And renal is just another
word referring to kidneys, and we've got renal veins with
blood flowing back out of them. So once the blood is
headed back to the heart, we call it a renal vein. And there are two of them. And probably the most important
part about these kidneys, certainly the thing that
makes them really unique, is that they have these ureters. And these ureters drain
urine into a bladder. And actually, I'll
draw that right here. That's the bladder. And the ureters are the third
tube coming out of our kidneys. And then when you're
ready to urinate, you can release all that
urine from your bladder into the outside world. And so there are
three basic things that I want you remember coming
into and out of kidneys-- the renal arteries and the
renal veins and the ureter. Now, to really make
sense of it, you've got to think about how
the artery might split up. So let's say we go back to
the artery and you follow it, and it starts kind of branching. Let's say it makes
five little branches. And then it might have more
branches off of those branches and finally maybe even
some more branches, and eventually it's not
even an artery anymore. Right? All these little
branches are so tiny, you would call them arterioles. And let's just take this
arteriole, this little guy, and let's see what happens. So let's say I take
that little guy and show you on the left
side of the screen what that would look like. So let's take a look at this
arteriole a little bit closer. So this is our Afferent
arteriole, A capitalized. And it's called Afferent because
it's headed toward something. Afferent arteriole. And let's not forget
where it comes from. It's coming from the
renal artery headed towards something, and
that something is this. The artery-- or the
arteriole, rather, starts making a lot of
little turn-backs on itself and finally straightens out. And when it does we call
it the Efferent arteriole. So that's how we keep straight
whether it's coming or going from this little network,
if you want to call it that, of blood vessels. And in fact, this little
network of blood vessels, if you look under a
microscope, is actually being hugged by
something like this. This is actually
really interesting. This is the first time we're
taking a look at something that is not a blood
vessel in the kidney, and it begins our
journey of urine. So this thing is called
the Bowman's capsule. This is the thing in yellow
that I've drawn for you. And whenever things
are named like this, you've got to wonder,
who was Mr. Bowman? And Mr. Bowman, turns
out, was from England. Actually, he was a
very curious fellow. And so he looked
under a microscope. And he noticed that
if you look right where these little tufts
of blood vessels are, you can actually
see that there's something surrounding
each of them. And so he called that
Bowman's capsule, and so that's what we
still call it today. So England was laying claim to
parts of the kidney anatomy. You may not even
have known that. So that's Bowman's
capsule, and that's the first part of the nephron. I'll actually show you all
the parts of the nephron. So the next part of the
nephron-- and nephron just means kind of the unit of
the kidney that we care about. The next part is looking really
squiggly, very convoluted. Right? And I'm trying to draw it that
way purposefully, because I want to show you a way of
remembering that this is actually called the proximal--
because it's near the Bowman's capsule, so it's proximal--
convoluted tubule, because this is one long tubule,
like a little tube. And so this is the
proximal convoluted tubule. So basically, the next
part of the nephron, after it starts in
the Bowman's capsule, is the proximal
convoluted tubule. And then it gets into
kind of a long deep loop, long loop like that. And this loop is called
the loop of Henle. So you're seeing now part
three is Loop of Henle. Now, loop make sense. But of Henle, you've
got to wonder, again, is this another British guy? Who is Mr. Henle? Mr. Henle, it turns out,
is actually not British. But he's from another
part of Europe. Let's see if you can guess
before I finish this drawing. He discovered that if you
follow the nephron deep into the middle
of the kidney, it has these little loops, very
delicate loops, but very important in helping urine form. And he was a German scientist. And so if the British are
going to identify something, so will the Germans. And so we still call
that the loop of Henle. And after the Loop of
Henle, we have another area that's very convoluted. And so you can guess
what we call this where, because we're going to probably
try to stay consistent. And if the first part was called
the proximal convoluted tubule, we would call this
not the proximal, because now it's
not near anymore, but it's a little further away. We would call this
the distal, meaning further away, convoluted,
because it's still convoluted, tubule. So this is the distal
convoluted tubule. And finally, there's a
fifth part of all this. The fifth part of all this is
a giant tube of collection. So all this stuff goes
into a collecting tube. And I'm actually showing you
where all the other distal convoluted tubules might
be dumping in as well. Maybe there. And eventually all
this stuff is going to go to the same place,
which is down to the ureter. So we've seen now how
things go to the ureter. You can see how things
come from the renal artery. But you're probably still
wondering-- oh actually, I didn't label this for you. This is the collecting tube. You're probably
still wondering where is the renal vein in all this. I mean, I still drew
the Efferent arteriole as being red, and
it's got oxygen. So where does the
venous blood come from? And the answer is right here. So you basically get red blood
or oxygenated blood flowing over all these
parts of the tubule. So all the parts of the
proximal convoluted tubule, the loop of Henle, the
distal convoluted tubule, and the collecting duct
all get wonderful blood. And then finally, when
all is said and done, it all drains into one
thing, one final renal vein. And that's with all of
the blood coming together. So this little network
is considered-- this little network
of capillaries, then, is considered, right
here, the peritubular, going around the tubule,
tubular capillaries. And that makes sense. Now, you can see the
renal artery blood coming in, going in through
the Afferent arteriole, then the Efferent arteriole,
and then draining back into the peritubular capillaries
and finally, the renal vein. And this important structure
in yellow that I've drawn has five parts to it, and all
five parts coming together are called the nephron. And so this is an
important structure, and we'll talk about
different parts of the nephron in future videos. But this is an
important structure, to at least get a
sense for how it looks and what the different
parts are called.