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0:01[br]Voiceover: Imagine you're in a movie theater.[br]0:03[br]You're watching a really, really long movie.[br]0:05[br]And you've finished your entire bucket of popcorn.[br]0:08[br]You've guzzled down a giant soda[br]0:10[br]and all of a sudden, you have to pee.[br]0:12[br]And to make matters worse, you're watching a movie[br]0:15[br]about a whole bunch of people on a cruise ship[br]0:17[br]that hit an iceberg and so, there's a lot of water[br]0:20[br]in this movie and you freak out because[br]0:22[br]now you have to get up and go to the bathroom.[br]0:24[br]But then that should get you thinking,[br]0:27[br]well, how do my kidneys work?[br]0:28[br]How is it that I can make all this pee[br]0:30[br]that I have got to get rid of?[br]0:32[br]Well in the next few videos, we're gonna[br]0:33[br]talk about how the kidneys work.[br]0:35[br]And I'll give a quick overview here[br]0:36[br]before we delve more into the specifics.[br]0:39[br]As you can see, the kidneys sit[br]0:41[br]right here around your belly button.[br]0:43[br]They're about the size of a fist and you've got two of them.[br]0:47[br]And they sit a little closer[br]0:48[br]to the back, not really in the front.[br]0:50[br]So the kidneys receive blood from the heart.[br]0:52[br]So the heart goes on up here.[br]0:56[br]It's also about the size of a fist.[br]0:58[br]And it pumps blood throughout the body.[br]1:00[br]You know, you get some to your arms,[br]1:03[br]you have some that goes up to your brain,[br]1:05[br]and you have this branch that comes down[br]1:08[br]and it goes towards your legs, as well.[br]1:10[br]Well, what you can kind of see[br]1:12[br]in the picture of the kidneys right here,[br]1:14[br]is that they've got a little vessel right there[br]1:16[br]so sure enough, there's some blood that comes[br]1:18[br]from the heart into the kidneys.[br]1:21[br]Both of your kidneys, then, are going to[br]1:23[br]filter the blood and release urine,[br]1:26[br]which is just a collection of waste products[br]1:28[br]that your body wants to get rid of.[br]1:30[br]And the urine is gonna hang out[br]1:32[br]in your bladder that sits about right here,[br]1:34[br]until it's an appropriate time to go to the bathroom.[br]1:37[br]And that's kind of a broad overview.[br]1:38[br]But let's go into a little more detail[br]1:40[br]about what the kidneys do.[br]1:42[br]So I'm going to draw a box over here.[br]1:45[br]And this box is going to be what the kidneys do.[br]1:50[br]So I'm going to give just a really simplistic[br]1:53[br]overview of what the kidneys do.[br]1:55[br]And then in other videos, we'll go dive deeper into detail.[br]1:59[br]So as I mentioned, each of your kidneys[br]2:01[br]gets an oxygenated blood vessel,[br]2:03[br]or an artery that goes to them.[br]2:06[br]And your arteries hold onto all the things in your blood.[br]2:09[br]This can include things like your nutrients.[br]2:11[br]And so nutrients can be anything from say,[br]2:15[br]your electrolytes like your sodium ions.[br]2:18[br]They can be things like your proteins or your[br]2:21[br]amino acids or even glucose, as well,[br]2:24[br]things that build your carbohydrates.[br]2:26[br]So a lot of things that your body uses[br]2:28[br]as the building blocks, or things that help[br]2:30[br]other structures of your body work.[br]2:33[br]In addition to your nutrients, you've also got[br]2:35[br]oxygen hanging out in your arterial blood.[br]2:38[br]And your arteries also contain waste products.[br]2:41[br]So things your body has made through cellular respiration[br]2:44[br]and all these other processes that we undergo[br]2:47[br]that we don't need anymore, that we want to get rid of.[br]2:49[br]And they can include things like urea and other[br]2:52[br]toxic compounds that we don't want to build up.[br]2:54[br]And at the same time, it can also include[br]2:57[br]extra electrolytes, like sodium that we don't need.[br]3:00[br]Because if we hold onto a lot of sodium chloride,[br]3:02[br]which is just salt, we'll end up having high blood pressure.[br]3:05[br]So our kidneys also help us maintain our[br]3:08[br]blood pressure, as we'll talk about in other videos.[br]3:10[br]So, this just kind of underlines[br]3:12[br]the point that if you have too much[br]3:14[br]of your nutrients, they become waste products.[br]3:16[br]And so, your kidneys help to make sure you don't[br]3:19[br]build too much of this good stuff here.[br]3:21[br]So this is all the stuff you've got hanging out[br]3:24[br]in the artery that's coming over to your kidney, right here.[br]3:27[br]And as you might recall, whenever you have[br]3:29[br]an artery coming into an organ or a part of your body,[br]3:32[br]there should be a vein that takes the blood away[br]3:36[br]from it that's going to return it to the heart.[br]3:39[br]So this is your vein, right here.[br]3:41[br]And so the job of the kidneys then, is to make it so that[br]3:45[br]the nutrients you had in your arterial blood[br]3:48[br]are collected and maintained when we get to the vein.[br]3:51[br]So we want to hold on to our nutrients, right here.[br]3:53[br]So I'll just write "nutrients".[br]3:55[br]And it stands for all the stuff that I[br]3:57[br]gave examples for on the left side here.[br]3:59[br]And the kidneys, like every organ[br]4:01[br]in the body, need oxygen to do well.[br]4:03[br]So you'll have the oxygen go through the kidneys[br]4:05[br]and some of it will make it out.[br]4:07[br]Some of it will be used by the kidneys.[br]4:09[br]Because that's how we can maintain some of the tissue.[br]4:12[br]And so when we get to the other side,[br]4:14[br]where the vein is, we'll have less oxygen.[br]4:16[br]So I'll write it really tiny right here to show[br]4:18[br]that there's much less oxygen in your venous blood[br]4:21[br]than there was in your arterial blood.[br]4:23[br]And finally, the kidneys want to take all the[br]4:25[br]waste products your arterial blood brought[br]4:27[br]to the kidney and hold on to it, make it so that[br]4:31[br]this stuff does not end up in the venous outflow.[br]4:34[br]And by collecting these waste products,[br]4:36[br]the kidneys will effectively produce your urine.[br]4:40[br]Now, you might notice in this picture[br]4:42[br]that I am missing something.[br]4:44[br]What connects the artery to the vein?[br]4:46[br]Well actually what goes on here[br]4:48[br]is part of what makes the kidney so special.[br]4:50[br]And it answers the "how".[br]4:52[br]How is it that the kidneys are able to do this?[br]4:55[br]How is it that the kidneys can help us[br]4:57[br]maintain our nutrients in our body[br]4:59[br]while getting rid of waste into urine?[br]5:01[br]Well, the kidney is special[br]5:04[br]because it's got two capillary beds.[br]5:07[br]I think you might have heard[br]5:09[br]what a capillary is before, alright?[br]5:11[br]A capillary bed is just something that[br]5:14[br]connects the artery and the vein.[br]5:16[br]It's where you can have oxygen flow out.[br]5:18[br]You can have nutrients flow in.[br]5:20[br]So the way I'll draw it is that you've got one[br]5:23[br]capillary bed, right here, connecting your[br]5:24[br]artery to your vein, like that.[br]5:27[br]And you've got another one down here connecting those two.[br]5:31[br]And so these guys work together to deliver oxygen[br]5:36[br]to the kidney's tissue and, at the same time,[br]5:39[br]recollect these nutrients so that the vein can[br]5:42[br]take these nutrients elsewhere in the body for use.[br]5:45[br]And these capillary beds have two fancy names.[br]5:47[br]The first one is called the vasa recta.[br]5:52[br]The vasa recta.[br]5:53[br]And that's mainly to give oxygen to the kidneys.[br]5:57[br]The other set of capillaries are[br]5:59[br]called peritubular capillaries.[br]6:04[br]Peritubular capillaries, and we'll talk way more[br]6:07[br]into detail about these peritubular capillaries.[br]6:10[br]And these are the guys that are mainly[br]6:13[br]going to be responsible for collecting[br]6:15[br]nutrients that our kidneys will filter.[br]6:18[br]And we'll talk more about that[br]6:20[br]process in the next few videos.