If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content
Current time:0:00Total duration:6:24

Video transcript

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