hi and welcome to this video on the start of the urinary system so head there right now all right so what we're looking at first there we go um are just the components of the urinary system so we have kidneys well their job is to filter our blood and um it's always I don't know what color all right so filter a blood remove waste products convert the filtrate into urine now it's important we understand there's a difference between filtrate and a difference between urine that we'll get into later then in the anatomy portion of this so with the lab um we'll go over ureters kidneys to urinary bladder what the bladder is and what the urethra is so here these pictures so we're not going to even do any of those because those will all be done in lab so here is what your kidney does okay so number one elimination of metabolic wastes those metabolic wastes are primarily nitrogenous wastes which we will get from protein digestion will be urea oh because we're trying to get rid of the nitrogen so protein has nitrogen in it and nucleic acids do as well and so nucleic acid waste is uric acid um regulation of ion levels very very important we can also just put electrolyte levels because we'll talk more about that in the fluid and electrolyte balance chapter so sodium potassium calcium regulation of acid base balance hydrogen ions and bicarbonate ions very very important regulation of blood pressure okay so the long term regulation of blood pressure is managed by the kidneys elimination of biologically active molecule drugs so hormones okay so things with half-lives why do they have a half-life because half of them went out in the kidney drugs this is why we do urine testing because those things are going to show up in our urine okay and then formation of calcitriol so this is active vitamin D if you remember vitamin D is made in the skin so it'll be made as inactive oops vitamin D and we call that choli calciferol and then we have to change it into calcitri trial so then that'll be active vitamin D3 production release of earthropoietin we did this already in the hormone chapter um we did it in the blood chapter and now we're doing it again in the urinary system chapter is erythropoietin or EPO in response to low blood oxygen in the tissue so we call this hypoxia um the the cells of the kidney will produce erythropoietin which will then stimulate the red bone marrow to increase erythrocyte production so rbcs okay and then to engage in potential gluconeogenesis this is mostly done by the liver if I have to um if my if my liver isn't functioning properly my kidneys can do that or if I'm in prolonged fasting and starvation I've got to get the glucose from somewhere because remember what is it all about yep it's all about cellular respiration so what is the substrate for cellular yeah that's right what is a substrate for cellular respiration it's right there it's glucose please remember this chemical formula forever and ever and ever C6H12O6 is glucose all right so we can make glucose from non-carbohydrate sources primarily proteins and fats and so if we don't have enough carbohydrate uh nutrients then we can get our carbohydrates for um glycolysis and um and aerobic respiration from proteins and fats okay so um this gross anatomy not going to do here I'm just going to leave in it leave it all here but we're not going to do any of this um will you well okay so let me um let me just talk to you about this really quick so if your kidney sags do you have ptosis like eyelid you know if your eye lids dropping um well have enough adipose um then you make kink your ureter blocks urinary flow urine backs up swelling of the kidney hydronephrosis can lead to kidney failure hydronephrosis can also be caused by kidney stones renal calculi I just love that name um kidney stones and that is also part of the pain that we get when we have kidney stones and I have problems with kidney stones and I'll probably tell you more about them as we go through this video or this set of videos all right so um other kidney variations abdominal may not even get one the kidney doesn't migrate from the pelvic cavity up into the abdominal cavity horseshoe they stick together or you may develop more of a kidney stuff all right um that we're not going to do this either so this should already be in all the lab portion of the um that and the parts of a nephron I think I'm going to um reiterate the portions of the Nephron because it's so important but you should have also learned this in lab as well so what is a nephron well the nephron is function so this is what does the the job of the kidney so this is what we can call the basic functional unit of the kidney so it's the thing that's going to do the job so what is it it's a Nephron and the associated collecting ducts and tubules and anything else that may be associated with it like blood vessels capillary beds that are associated with it as well all right so microscopic functional filtration unit of the kidney we have a renal corpuscle and a renal tubule we'll get into all of that this is important to know all of the corpuscles so everything that is in the corpuscle and most of the tubule will be in the cortex so if we look at the cortex of the kidney here is the dividing line the cortical medullary boundary Okay so all of this is cortex and the blood vessels are only in the cortex they're not going to be in the medulla and then here is the medulla all right so renal cortex renal medulla all right so in corpuscle is made of the glomerulus and the glomerular capsule so you need to know those two parts so if we go here to this picture of a nephron this is the corpuscle so here you can see the coarse puzzle it's going to be this section right there so in that you'll have the glomerulus and then the glomerular capsule and then you will have a visceral layer of the capsule which we'll look at bigger here in just a minute a parietal layer and a capsular space hey then we have um what is a glomerulus so it is a tangle of capillary Loops um well Muriel or capillaries it looks like a ball of yarn that's where we get glomerulus from is that it's a ball of yarn blood enters the glomerius the afferent arterial we absolutely need to know that and the blood exits through the efferent arterial so if we look at a picture whoops of that um this will be my afferent arterial as the blood is going into the glomerulus this will be my efferent arterial as the blood is leaving the glomerulus okay all right then the oh let's see I yeah but to pause this for just a minute I don't have a picture of the Glorious that I want you to see so I'll be right back okay I'm back there just weren't enough pictures in this for me so here we go all right so here is the renal corpuscle again I'm just gonna now there's too many pictures so I'm going to show you a bunch of pictures of um our renal corpuscles so let's get into a color that we'll be able to see all right so um we said that there was a glomerulus so here is the glomerulus so that is the ball of capillaries and then we have the glomerular capsule in our renal corpuscle so blood's going to come in through the A-frame arterial you can watch the arrows it's going to swirl around in here and as it swirls around in here we're going to produce some filtrate and then it's going to come back out and go out through the efferent arterial all right then the glomerular capsule is going to have two layers to it so the parietal layer right here is just going to be regular simple squamous epithelium and then we have a visceral layer that are made up of these interesting cells I kind of like them talk about them like octopus cells because they have all these arms that come off of them and wrap around and everything so um visceral layer is made of cells called podocytes and will look more at their structure in a little bit and then between the two where these green arrows are going this is known as the um capsular space so everything that comes out of the glomeruli will go into the capsular space we have a vascular pole we have a tubular pole so this is the front end and the two the vascular poles the front end of the of the renal corpuscle and then the tubular pole is the back end of it okay I feel a lot better about that all right then there's a bunch of other things that will not worry about for a minute well we'll come back to that we're in that last picture all right so this is done a real nice job afferent arterial coming in glomerular capillaries efferent arterial going back out here is the parietal layer right there and then what happens so if we follow the parietal layer around it's going to be like we sh like a serious membrane you know how we shoved the um the organ into the serous membrane so we're going to push into it and then these cells out here these simple squamous epithelial cells here as they become the visceral layer because that's going to be the layer that touches the blood vessels they're going to change their shape and they're going to change into the octopus cells called the podocytes so glomerular capillary is covered by the podocytes that form the visceral layer of the glomerular capsule so they're just going to come out and they're going to just wrap around all of the portion of the glomerulus and then they're going to produce what's known as part of the filtration membrane which we'll be looking at in a little bit so we just continue on with that renal corpuscle we've got the internal permeable visceral layer with the photocytes photo sites and there's um filtration slits in there that we'll talk about their importance and then lies directly over the glomerular capillaries then we have an impermeable parietal layer simple squamous epithelium that's going to hold all the filtrate in and then the capsular space in between receives the filtrate which we will modify as it goes through the tubule to become urine then we have the vascular pole as I said that's where the blood vessels come in and then the tubular pole is where we start the renal tubule and again one more dang picture just another way of looking at it we'll be taking a look at the function of juxtagomerular cells and the function of macula densa as we talk about regulation of filtration and then we have these additional cells mesangial cells we'll talk about those little those a little bit later they're like modified smooth muscle cells and they are here in between the capillaries so they're going to kind of wrap themselves around the capillaries if we go to this picture here we can also see the um mesangial cells are the um the EMG I don't know why it's because this is um Bridal epithelium and this is the glomerular basement membrane and this is the epithelium these are the meningo mesangios cells this is a podocyte this is the I don't know what they want to do this for school marrying their capsule a for an arterial efferent arterial macula densa so all of this extra granular mesangel cells that's what that stands for um so there's Miss Angeles we'll talk more about those later all right so this is nice this shows the capillary so all the tubes and then all of this this is all a podocyte and you can see it's just going to take its extensions and wrap them around and then it has these little fingery um things that come off of them that interdigitate and then make filtration slits so the large cell bodies as the potocytes give rise uh rise to the Fine foot process yeah that's what they're called so these little thingies that come out are called foot processes and sit on the outside of the glomerular capillary wall and form the pores so all of these little slits these dark places that's where the filtrate is going to come through so we are in the glomerular capsule from this view we are um bloating in the filtrate so to speak if we're in this view all right so that is the renal corpuscle and so now we want to go into the renal tubule so we have three parts of the tubule the proximal convoluted tubule the nephron loop which we are going to continue to call the loop of henle and then the distal convoluted tubule so proximal convoluted tubule by virtue of its name what is it proximal two proximal to the capsule so it is the start of the tubule first region um starts the renal Pole or the tubular pore of the renal corpuscle simple cuboidal epithelium okay very very important lots of microvilli to increase the surface area and reabsorption capacity because it is in the proximal convoluted tubule where a majority and we'll be talking about this later majority of reabsorption occurs so as we filter our our blood um when we talk about exactly how it does that within the glomerulus or from the glomerius to the glomerular capsule we'll we'll mention the fact that hey we don't really control what's coming out of your bloodstream just as long as it's smaller than the hole it's going to come back it's going to come out but that means there's going to be a lot of good stuff in there as well there's a lot of bad stuff so we want to keep the urea in the in the filtrate to become urine but all the rest of stuff like proteins or amino acids and glucose we want to reabsorb that material back into the bloodstream so we don't want it to leave as urine so um we need to have abundant microvilli for a surface area for reabsorption and then we're also going to have this um magical I think I mentioned it in the digestive system video but if I didn't no I think I did but here we're really going to talk about this um is this transport protein called sglt1 um transport protein and that is what's going to be just studied in the microvilli and it's through these sglt ones that we do a majority of our absorption and reabsorption of glucose and sodium and so it's really important and we will talk about that later when we talk about reabsorption all right then the loop or the and I'm going to keep doing this Loop of henle is a Bend so the PCT is going to be coming along and it's going to bend okay so right here it's going to become the loop and then it's going to bend out again and then so this is piece whoops PCT Pokemon Blue tubio distal convoluted tubule and loop of Henley all right so we have a descending limb because we're going to go this way and then we're going to swing around and come this way descending limb which is going to be primarily thin which means the thin portions are lined with simple squamous epithelium I don't know that I want to say lined with they're composed of positive and then the thick segments which are primarily found in the ascending limb are Sim we've transitioned back into simple cuboidal epithelium again and you will see how that works in just a minute and then we come to the distal convoluted tubule so that's the end extends to the collecting tubule cubal simple cuboidal epithelium with out microvilli um few and definitely appears clear when viewed with the light microscope because we've absorbed all of the mushy stuff and if I put this the oh tissue slide in there I might not have put that in there I may have to put it in when we after this video when we go into the next one um you can definitely tell when you're looking at kidney tissue under the microscope you can tell which tissue is proximal because it's very um not clear in the middle of the tubule which means the material hasn't been absorbed reabsorbed yet so there's still a lot of glucose and amino acid and and other substances like that that are still in the proximal convoluted tubule but by the time you get to the distal convoluted tubule all of that mushy stuff should have been absorbed reabsorbed by then so um so you only have um mostly water and some sodium left in the distal convoluted tube so the the tubule looks empty when you see it through a light microscope the the proximal convoluted tubule looks like it's got stuff in it it's kind of cool actually it's really cool friends because tissues are the best that's you know that's what I want to do is look at tissues all day okay but I also want to be here with you so there you go all right so here is our renal corpuscle glomerulus glomerular capsule proximal convoluted tubule so let's follow the proximal convoluted tubule so it's going to be green I'm going to change it colors so oh look at that why does it loop around so much well because I need a really long length of tubule but I only have a tiny little space to put it in so I'm going to fold it all up on itself so then I'm going to come down here I'm still proximal convoluted tubule friends boom boom okay now I'm going to transition into um Lupa Henley so you can see some of the descending limb is thick but primarily the descending limb is going to be thin oh we'll just do the whole thing and then ascending limb but notice that the ascending limb transitions into a thick portion right here and then it's going to travel up here boom and then we're going to become the distal convoluted tubule it's so hard for me to choose a color and so this is the distal convoluted tube okay then we'll get hook into these little tubules right here which are the collecting tubules where the urine is going to dump into this one big thing called a collecting duct okay all right so that's how that works if we want to look at it as far as the tissue is concerned which is a really good idea to look at like this um here you can see in the proximal convoluted tubule simple cuboidal cells lots of microvilli okay so lots of microvilli so this border this purple border or blue border whatever it is how it's all folded up there on the top then we come to the nephron loop here you can see in the thick segment this is going to be simple cuboido but then we've transitioned to the thin segment so then that's going to be simple squamous and then we come back to the simple cuboidal again then and we're in the distal convoluted tubule you can see there's some microbial IV screen things so some microvilli but not anywhere as abundant as what we have in the proximal convoluted tube and then our collecting duct cells made of intercalated discs and circulated discs interculated cells and principle cells we'll talk about those much later all right now um based on the structure of a kidney I'm just going to draw this really rough kidney right here picture in a minute okay so remember we have the outer portion that's called the cortex then we have this inner portion called the medulla now the cortex is going to have a bunch of cells into it referred in it referred or not cells but nephrons in it known as cortical nephrons they have a very short Loop of henle barely dips down into the medulla and 85 percent of our nephrons are cortical nephrons just to filter our blood but then we also need to have some um other ones who are right next to the cortical nephrons are kind of right up in there and then the juxta medullary ones I'll show you are like that so they have a little bit of their structure the glomerulus and the or the renal corpuscle I guess we could say the renal corpuscle is always going to be in the cortex because the renal corpuscle always has blood vessels in it and so the blood vessels are only in the cortex so um that we're going to filter so um uh regardless of what kind of nephron you're talking about cortical nephrons or juxta medullary ones the corpuscle will always be in the cortex but in the juxta medullary ones they're so close to the medulla juxta means to place next to that their Loop of henlee descends down into the medulla and there's a reason why we need to do that so um the juxt imaginary nephrons are they have long nephron Loops go down into the medulla and they are involved in regulating the concentration of our urine Okay so water concentration in urine oh urine okay we want to produce dilute urine and it's our juxtaposulary nephrons that are going to help us do that so here just shows um how they work so here's a cortical nephron you can see that its Loop of henle is just this little bit down into the nephron but if you I mean into the medulla but if you look at the juxta medullary ones look at all of its Loop of family really long Loop of Henley is going to be here completely within the medulla okay so in the cortex cortical nephrons next to the medulla juxtapedulary nephrons and we'll be coming back and talking about them later all right um so nephron's drained to a collecting tubule that drains into collecting duct so tubules into collecting Ducks uh if you want to think of the Nephron nephron this is the um water pipes in your house or the water pipe from drains and toilet so all that water that you want to get rid of that's going down the drain and is going um through your toilet into your sewer pipe in your house that's a nephron then this is your sewer pipe to the street sewer to the street and your collecting duct is the sewer pipe in the street that all the houses hook to so every house has its own set of water drains and then it has its own sewer pipe to the street and then the street itself has the sewer line right and then all the houses hook into the same sewer line that's what the collecting duct is so several nephrons are going to hook into the um into the collecting duct all right and then we're not going to worry about the rest of that um so in the collecting duct we're going to have principal Styles which are going to be responsive to hormones of aldosterone and ADH to regulate sodium and water balance because that's our printable job right that's how I like to think about it and then the interculated cells are going to help regulate PH by secreting or absorbing hydrogen ions all right so if okay this is great we can look at this um all right so let me scoop this over right here so if we take a look and I just I don't even have a pointer or anything anymore um um so if we Sorry my daughter just texted me okay so if we look at the proximal I wish that I when it's big I lose my pointer ability so look at the highlighted proximal convoluted tubule um and uh so our proximal convoluted tubule has stuff in it so you can see it looks kind of pinkish inside of there and that's because there's filtrate in there um and then the distal convoluted tubal doesn't have anything in it that you can see it's been reabsorbed so let me just Escape out of this and now I have a pointer okay I just want you to be able to see bigger so back to just go and go back to green okay so all of this right here that stuff that hasn't been reabsorbed but see look how this is how clear that is so distal convoluted tubules are clear proximal convoluted tubular murky so proximal I miss scribble in proximals let's find some more proximals um here's a proximal here's a proximal and can you see how they're all folded up on each other so even the proximal and the distal convoluted tubules they just fold up on each other and so if we look at um let's see let me make it bigger all right so what are we what are we looking at is a cross section so see where they put that transverse plane in there so we're looking at all of that so we can see yeah there's going to be proximal convoluted tubules and distal convolute tubules all mixed in with one another then if we go to if we go to the medulla then we'll be able to see thin segments of the Nephron and so they're going to be small because remember they're thin they're just tiny little um simple squamous epithelium then we'll see the thick segments because this is simple cuboidal this is simple squamous and then our collecting decks are big and then a vasor recta that's a capillary talk about those later all right now um in our there we go so we'll take a look at this picture again in a minute all right so in order for us to regulate filtrate formation and systemic blood pressure we need this juxtaglomerular apparatus so in another video we will be looking at how do these work specifically in regulating blood vessel Urban blood pressure in in GFR but um right now we're just giving you a little introduction into them so JG cells are made of granular cells they are also known as juxtaglomerular cells so we may see them as JG cells maybe there's some information I have in here that still calls them JG cells um so modified smooth muscle of the afferent arterial their job so their mechanoreceptors so they contract when stimulated by Stretch super important or sympathetic stimulation and their job and we'll talk all about why and then they're right near the entrance of the renal corpuscle they synthesize store and release renin so JG cells release renin really important okay macula densa so the macula densa is another set of cells so modified cells in there they distal convoluted tubule then right next to the afferent arterial and their job is to be chemoreceptors so chemo receptors um of sodium chloride concentration so they will signal the granular cells to release renin through paracrine so Perkins when you're right next door and you live next door and you just go knock on the door instead of going in the bloodstream um and they will stimulate when systemic what was but blood pressure is low for now and then we'll talk all about that okay the extra glomerular mesangel cells so these are um uh around the glomerulus so they're just outside the glomerulus they're in the gap between the affair and efferent arterials they communicate with other jdg cells or cells of the JG apparatus their function is not well understood but they um uh increase um or decrease we'll put um let's see renal plasma flow which we will talk about how how much filtration is going to happen um but we'll get into that later okay so here are the mesangel cells here are the JG cells where's the listed the pointer oh there we go so I don't like this JG cell let me show you a bit better picture of JG cells um and then macula densa here's the macula densa let's go back really quick okay um see the JG cells or the granular cells that's these right here so they are right around the afferent arterial here are the cells in the macula densa and then here are the extra glomerular mesangel cells so they're all these gray cells that are all right around in here okay so all right um okay so that just goes over that I am not I'm just going to leave this but we're not going to cover this not your notes not your notes all right but we do want to know this so blood is going to come in to be filtered to the Nephron okay two the Nephron through the affair and arterial form the glomerulus some plasma filtered here well not all of your plants because you don't have just one afferent arterial you have a million or two million I guess you have a million per kidney so you have about 2 million afferent arterials efferent arterial takes the blood away from the glomerulus and becomes either the peritubular capillaries or the vasorecta peritubular capillaries are for reabsorption what are we going to reabsorb into or what are we going to secrete from absorption or secretion and then the afferent arterial and efferent arterial will be what gives the blood for filtration because filtration will happen at the glomerulus and then take the blood away that has been filtered so peritubular means around the up around the tube so it's going to intertwine themselves around the PCT and the DCT and they are going to be in the cortex with the cortical nephrons primarily with the cortical nephrons then the vasorecta is around the nephron loop and this is in the medulla now all blood moves to the two capillary bits filtered at the glomerular capillary beds goes through the peritubular capillaries or vasorecta for gas exchange nutrients and wastes and then finally into a network of veins which we aren't going to name but there they are and here is the picture so this just shows all the different branching of the blood vessels but when we get into the interlobular vein or interlobular arteries where are they okay so all the interlobular arteries are going to give rise to dozens of afferent arterials and those afferent arterials will then become glomeruli which will then all come together into an efferent arterial and then you will either become a paratubular capillary so that's these guys right here that are around the DCT and the PCT or you'll become a vasorecta here which goes around the nephron but the vasorectas usually oh I didn't put that on here um oops with the uh juxta medullary nephrons okay so what is going to happen at this point we are going to form filtrate so I am going to stop this video right here and then we'll start the next one on how do we form filtrate so that is all for