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Voiceover: Imagine you're in a movie theater.
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You're watching a really, really long movie.
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And you've finished your entire bucket of popcorn.
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You've guzzled down a giant soda
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and all of a sudden, you have to pee.
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And to make matters worse, you're watching a movie
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about a whole bunch of people on a cruise ship
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that hit an iceberg and so, there's a lot of water
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in this movie and you freak out because
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now you have to get up and go to the bathroom.
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But then that should get you thinking,
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well, how do my kidneys work?
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How is it that I can make all this pee
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that I have got to get rid of?
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Well in the next few videos, we're gonna
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talk about how the kidneys work.
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And I'll give a quick overview here
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before we delve more into the specifics.
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As you can see, the kidneys sit
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right here around your belly button.
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They're about the size of a fist and you've got two of them.
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And they sit a little closer
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to the back, not really in the front.
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So the kidneys receive blood from the heart.
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So the heart goes on up here.
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It's also about the size of a fist.
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And it pumps blood throughout the body.
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You know, you get some to your arms,
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you have some that goes up to your brain,
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and you have this branch that comes down
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and it goes towards your legs, as well.
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Well, what you can kind of see
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in the picture of the kidneys right here,
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is that they've got a little vessel right there
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so sure enough, there's some blood that comes
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from the heart into the kidneys.
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Both of your kidneys, then, are going to
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filter the blood and release urine,
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which is just a collection of waste products
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that your body wants to get rid of.
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And the urine is gonna hang out
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in your bladder that sits about right here,
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until it's an appropriate time to go to the bathroom.
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And that's kind of a broad overview.
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But let's go into a little more detail
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about what the kidneys do.
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So I'm going to draw a box over here.
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And this box is going to be what the kidneys do.
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So I'm going to give just a really simplistic
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overview of what the kidneys do.
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And then in other videos, we'll go dive deeper into detail.
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So as I mentioned, each of your kidneys
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gets an oxygenated blood vessel,
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or an artery that goes to them.
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And your arteries hold onto all the things in your blood.
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This can include things like your nutrients.
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And so nutrients can be anything from say,
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your electrolytes like your sodium ions.
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They can be things like your proteins or your
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amino acids or even glucose, as well,
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things that build your carbohydrates.
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So a lot of things that your body uses
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as the building blocks, or things that help
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other structures of your body work.
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In addition to your nutrients, you've also got
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oxygen hanging out in your arterial blood.
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And your arteries also contain waste products.
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So things your body has made through cellular respiration
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and all these other processes that we undergo
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that we don't need anymore, that we want to get rid of.
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And they can include things like urea and other
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toxic compounds that we don't want to build up.
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And at the same time, it can also include
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extra electrolytes, like sodium that we don't need.
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Because if we hold onto a lot of sodium chloride,
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which is just salt, we'll end up having high blood pressure.
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So our kidneys also help us maintain our
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blood pressure, as we'll talk about in other videos.
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So, this just kind of underlines
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the point that if you have too much
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of your nutrients, they become waste products.
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And so, your kidneys help to make sure you don't
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build too much of this good stuff here.
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So this is all the stuff you've got hanging out
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in the artery that's coming over to your kidney, right here.
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And as you might recall, whenever you have
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an artery coming into an organ or a part of your body,
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there should be a vein that takes the blood away
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from it that's going to return it to the heart.
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So this is your vein, right here.
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And so the job of the kidneys then, is to make it so that
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the nutrients you had in your arterial blood
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are collected and maintained when we get to the vein.
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So we want to hold on to our nutrients, right here.
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So I'll just write "nutrients".
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And it stands for all the stuff that I
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gave examples for on the left side here.
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And the kidneys, like every organ
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in the body, need oxygen to do well.
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So you'll have the oxygen go through the kidneys
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and some of it will make it out.
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Some of it will be used by the kidneys.
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Because that's how we can maintain some of the tissue.
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And so when we get to the other side,
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where the vein is, we'll have less oxygen.
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So I'll write it really tiny right here to show
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that there's much less oxygen in your venous blood
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than there was in your arterial blood.
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And finally, the kidneys want to take all the
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waste products your arterial blood brought
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to the kidney and hold on to it, make it so that
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this stuff does not end up in the venous outflow.
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And by collecting these waste products,
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the kidneys will effectively produce your urine.
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Now, you might notice in this picture
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that I am missing something.
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What connects the artery to the vein?
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Well actually what goes on here
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is part of what makes the kidney so special.
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And it answers the "how".
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How is it that the kidneys are able to do this?
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How is it that the kidneys can help us
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maintain our nutrients in our body
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while getting rid of waste into urine?
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Well, the kidney is special
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because it's got two capillary beds.
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I think you might have heard
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what a capillary is before, alright?
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A capillary bed is just something that
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connects the artery and the vein.
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It's where you can have oxygen flow out.
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You can have nutrients flow in.
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So the way I'll draw it is that you've got one
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capillary bed, right here, connecting your
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artery to your vein, like that.
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And you've got another one down here connecting those two.
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And so these guys work together to deliver oxygen
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to the kidney's tissue and, at the same time,
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recollect these nutrients so that the vein can
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take these nutrients elsewhere in the body for use.
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And these capillary beds have two fancy names.
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The first one is called the vasa recta.
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The vasa recta.
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And that's mainly to give oxygen to the kidneys.
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The other set of capillaries are
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called peritubular capillaries.
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Peritubular capillaries, and we'll talk way more
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into detail about these peritubular capillaries.
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And these are the guys that are mainly
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going to be responsible for collecting
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nutrients that our kidneys will filter.
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And we'll talk more about that
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process in the next few videos.