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Class 10 Biology (India)
Course: Class 10 Biology (India) > Unit 1
Lesson 8: ExcretionParts of a nephron
Learn about the 5 major parts of the kidney's nephron. Rishi is a pediatric infectious disease physician and works at Khan Academy. Created by Rishi Desai.
Want to join the conversation?
- if the kidneys are so important than how can we live with just one?(20 votes)
- There are two reasons why people can live with a single kidney: 1) glomerular hypertrophy of intact nephrons and 2) tubular cell growth. Glomerular hypertrophy of the nephron is accompanied by afferent arteriole dilation increases capillary filtration pressure. Hypertrophy and afferent arteriole dilation can raise single nephron GFR as much as 50%. Tubular cell growth of the intact nephrons also increases the surface area for tubular reabsorption and secretion, and improves the ability to maintain homeostasis for a variety of small molecules and electrolytes. In chronic kidney disease, a disease that chronically destroys kidney tissue, adaptive growth of the kidney is so effective that kidney disease will not affect the kidney until 80-90% of the kidneys are lost. That is how people are able to live with a single kidney.
Also as a tip: think A-afferent-approaching arteriole; think E-efferent-exiting arteriole.
Hope this helps! :)
source: my pathophysiology notes(13 votes)
- I always associated kidneys with waste removal (aside from the glandular functions),so I was surprised to learn that it is an arteriole that distributes fluid to the uretur,rather the a venule. I suppose that the waste removal is not the focus here, but a byproduct of the kidneys main focus which would be fluid balance in the body?(5 votes)
- http://upload.wikimedia.org/wikipedia/commons/thumb/2/2e/2611_Blood_Flow_in_the_Nephron.jpg/725px-2611_Blood_Flow_in_the_Nephron.jpg
The structure is a clearer in this image. Basically blood is filtered at the glomerulus, then it continues through the efferent arteriole, through the peritubular capillaries to the vein. Where as the waste from glomerulus gets collected into the ureter.(5 votes)
- Why is this video in blood pressure control? It doesn't make sense to me, it's just like any other part of the body. there are arteries, arterioles, and capillaries.(3 votes)
- The kidney is key to blood pressure control. Angiotensin and aldosterone play major roles. To understand their action, you have to understand the structure and function of the kidney.(6 votes)
- at 5min - the loop of Henle - is there anything specific about the "thick part" of the loop of Henle? The capillaries in the nephron - are these "Fenestration" capillaries?(2 votes)
- Yep, these capillaries are fenestration capillaries :)
I'm not sure if they explain it in these videos here, but the "Thick Ascending Limb" of the loop of Henle absorbs sodium (Na+). This is so that water can be absorbed in the "Thin descending limb" of Henle. This mechanism is called "counter current multiplication". It's weird but cool, and the main basis of it is to absorb water quickly, as other parts of the nephron are designed to absorb sodium, potassium, and also chloride and calcium. Your body will prioritise absorption of sodium however.(2 votes)
- Where do kidney stones form? (If at all in the nephron)(2 votes)
- Isn't the renal vein smaller than the renal artery?(2 votes)
- Veins are almost always larger are they not, they have a lower blood pressure because of it(1 vote)
- Its not totally clear from the drawing but i assume that the arteriols go over the collecting tube as well since i it will also need oxigen. And it is just drawn as if the veins start "early"(1 vote)
- The efferent arteriole leads to a capillary network that surrounds the rest of the nephron. Most instructors don't draw in all the details of the capillary network because it covers up the nephron. Google 'nephron' and click on images and you'll find one with all the capillaries drawn in.
Russ Palmeri MD(2 votes)
- What do the tubules actually look like? Are they about the size of the tiny capillaries near the surface of your skin? How much fluid can a nephron process in a minute? Thanks!(1 vote)
- What is the red squiggly thing at the very beginning between the afferent and efferent arterioles?(1 vote)
- This represents the special capillaries called the glomerulus which are inside Bowman's capsule. This is where materials in the glomerular capillaries filter into the capsule and start their journey in the nephron.(2 votes)
- are the renal artery and renal tubule the same?(1 vote)
- No, quite different. Renal tubule is part of the nephron, while the artery is a branch of the circulatory system supplying the kidney.(1 vote)
Video transcript
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.