hi and welcome to part two on the urinary system we're going to talk about filtrate formation and wherever we get in this video we'll just see so all right so what is filtering so as the blood flows through the glomerulus water and solutes will be filtered from the blood plasma and so whatever can move across the glomerular capillary wall and into the um and into the capsular space will then be called filtrate now filtrate is not urine okay so it's not urine because we are going to reclaim a lot of material that's in the filtrate we're going to reabsorb it and then we're also going to add back from the blood capillaries any substances that didn't get filtered in adequate account accounts amounts or quantities that's what I was trying to put together um through the process of tubular secretion so the kidney does or the nephron does three processes it does filtration reabsorption and secretion and we will take a look at where that happens so tubular fluid is now the name of the filtrate once it enters the proximal convoluted tubule so this is going to be reabsorption reabsorption reabsorption well I have a little bit in here and then this will go into the um into the um renal papilla renal pelvis papilla are the little ends of the of the medullary pyramids but the pelvis is where we're going to collect urine and then we're going to go out the ureter I don't know the bladder oh which we're going to look at in the next slide as I look at my at my preview so once urine enters the Pilla and we'll take a look at where that is here in just a minute um we go into a calyx and we go into the pelvis and we go to the ureter and we go to the urinary bladder and then we leave through the urethra so I love this picture I'm going to go ahead and magnify it all right so we take a look up here up in the green portion where it says capsular space so that's where the filtrate is going to form now we're going to move into the orange part this is now tubular fluid because it is in the tubule so tubular fluid will be found in Parts two three four five six and seven so that's all um well tubular fluid I still refer to it as filtrate until it gets down here to the papilla so the very bottom of the of the renal pyramid and then it's going to drip out through those little holes you can see that papillary duct then it's going to enter into the calyx at the minor calyx are cups that surround each one of the renal pyramids and then the cups come together into two or three minor calyces at number 10 and then the calycy or major calyces excuse me and then the candices will come together into number 11 the renal pelvis now the renal pelvis is where we get kidney stone formation so as the urine is being held in the kidney before it leaves through the ureters and goes to the bladder um it hangs out in the renal pelvis and so that's where you will find kidney stones is in the renal pelvis and then and they don't hurt when they're in there I probably still have a bunch more I had a I had a um ultrasound on my yeah um small intestine I was having some enteritis and just really sharp pains and uh so we did the ultrasound to see you know just what's going on in there to have any kind of weird blockage or some gallbladder issue or something like that and um so then um they well and it happened to be one of my students who was the ultrasound tech and and uh one of my former students and so he uh he said oh I can still see your kidney stones in there so I was like well that's nice so kidney stones that I had not yet passed so I don't know how many of those um still have not passed anyway guess we'll see until I die then we're going to go down into the urinary bladder at 13. so the ureter is the tube that leads to the urinary bladder you have two of them one from each kidney and then urinary bladder and then out the urethra all right so let's look at how do we form urine uh obviously so like I said we're going to filter first filtration then reabsorption and secretion and reabsorption and secretion kind of go at the same time um we can have some secretion in early parts of the tubule but we can also have a bunch of secretion down at the end of the tubule so um glomerular filtration happens in the glomerular capillary so it's going to be from blood to tubule or from the capillaries to the tubule so we're going to take out water and dissolve solutes go into the capsular space And depending on how much is because of pressure differences across the filtration membrane how much force does the material come out with and how much can come out with that and then the separated fluid is called filtrate then we go to reabsorption now we're going to go from the tubule into the capillaries let's just put two capillaries so it could be peritubular or the vasorecta all right so how are we going to move it any way noticeable so I'm going to move by diffusion just normal diffusion and we will get into how do we how do we absorb all reabsorb all this stuff osmosis or active transport so tubules and collecting ducts oh there it is paratubular capillaries or vasorecta all vital solutes okay so what are vital solutes glucose we should reabsorb oops 100 percent of the glucose that we filter um and amino acids okay so vitamins those kinds of things that we need and most of our water is reabsorbed okay so we will filter 180 liters of blood but we will only produce one and a half liters of urine in a day and so we only eliminate one percent of what gets filtered now not one percent of our blood but one percent of what gets filtered okay so there you go and then excess solutes waste products some water will remain in the tubular fluid then we'll go into tubular secretion so this is movement of solutes by active transport out of the blood so we're going to go from the capillaries to the tubule from capillaries to tubule back into the tubule so that it can be eliminated not to be reabsorbed again we're going to do this to regulate PH so hydrogen ions potassium ions um uh drug metabolites so this is how we know um maybe some hormones how we know if we're doing random drug testing if we're doing a pregnancy test those kinds of things okay so here's where those happen so this is really great slide so glomerular filtration is going to happen from the glomerulus to the capsular space reabsorption is going to happen from the tubule whoops from the tubule so here's filtration out here is reabsorption in here's secretion back out okay and so we can do you can see we're doing it all over there isn't one specific place that we do reabsorption as opposed to secretion they're just going to happen from the tubule to the bloodstream for reabsorption or from the bloodstream to the tubule for secretion so this is a really monthliness up again um because that's beautiful all right so you might want to just really take note of that okay so how are we going to filter what are we going to um uh do to make this happen so we need certain characteristics of our filtration membrane it's going to be similar so similar to um respiratory membrane that we found between the alveoli the walls of the alveoli and the shared basement membrane and then the epithelium of the capillary so is porous it's thin it is very porous um very thin negatively charged um sorry uh formed by the glomerulus and the visceral layer of the glomerular capsule which we will see all right so what do we have so we're going innermost to outermost so we want the endothelium of the glomerulus remember the glomerulus is the capillary so this is the simple squamous epithelium of the wall of a capillary same endothelium that we've always seen except now these capillaries are the fenestrated ones remember we said there are continuous fenestrated and sinusoid capillaries these are the fenestrated ones so they have Windows in them Windows actually fenestrations are pores okay so they have pores in them that allow plasma and dissolved substances to pass so we're going to get what's known as bulk flow through here because we're not using transport proteins we're not using any specific structures to pick and choose what's coming through anything that is smaller than the whole okay so let's say smaller then the poor is going to make it through okay restricts the passage of large substances erythrocytes mostly large proteins I mean the erythrocytes is obvious I don't want blood in my urine but I also don't want proteins in my urine because if I pee out my proteins then I lose my colloid osmotic pressure and I don't want that basement membrane um so glycoprotein proteoglycan molecules are in that basement membrane restricts the passage of the large plasma protein so they can't fit through but they're also um it's also negatively charged oops oops negatively charged and we'll talk about that um well I'll just tell you right now proteins are negatively charged so is the basement membrane well the slit diaphragm which we'll look in a minute um because I don't think they specifically have the slit diaphragm in the definitions but I'll show you a picture so not only will the will the proteins like say you've got some small proteins those might fit through the fenestrations but they're going to be repelled back into the bloodstream by the negatively charged membrane okay so but I'll show you all of that in just a second okay so then the visceral layer of the glomerular capsule remember so this is going to be the outer layer around the glomerular capsule made of those octopus cells called protocytes octopus okay have long processes pedestals or foot processes um they they wrap around the capillary wall but they don't enclose it because we have the little filtration slits because the pedestals are going to inter intertwine with one another and restrict most small proteins from passing through and then we have mesangel cells that are going to be um I just what was I thinking um so the mesangial cells are going to be sorry about that um between the capillary Loops they are phagocytic they're contractile and we'll get into what purpose do they serve it has to do with how much filtration is going to go on um with contract and contraction and then signaling properties as well so here is a picture this is okay I have a better one so here is the endothelium mythical mirrorless right here oh let me go to a different color let me go to Yellow okay so here's my endothelium right here endotheliums here's my basement membrane that's two and then here are my filtration slits so these are the fenestrations stuff comes out and then it goes through the slits like that slips through um filtration slits all right so that whole section then is what referred to as a as a um uh filtration membrane but here is a little bit better filtration membrane so I have the fenestrated um capillaries of the fenestrated wall of the endothelium like it says the number one prevents filtration of blood cells but allows components of blood to pass through basal lamina or the basement membrane of the glomerulus prevents filtration of the large proteins then we have this slip diaphragm or the slip membrane and this is the one that's negatively charged so whoops negatively negatively charged so that any small proteins will bump into this and they'll go back through the pore so they'll be like well I can't get through here and they and for the most part they don't unless you have a damage filtration membrane like my father did oh I was going to mention the urinary system is my favorite system um my dad died of end-stage kidney failure because of high blood pressure and type 2 diabetes that he did not treat like he should have and um and it damaged his kidneys and so we'll talk specifically about what happened to my dad's filtration membrane um later on as we go through stuff but um uh he was stuff was going through that shouldn't go through and it wasn't filtering properly stuff was just flooding out into his urine and so then he had to go on dialysis because his kidneys did not do the work that they should and dialysis didn't really work for my dad and so um the head of the dialysis center where we were taking him got to the point where it was just draining the life out of him basically and she said you know what if this were my father I wouldn't bring him anymore and so we didn't and a lot of my former students worked there and so I would see them out in town and they would say well how's your dad doing because usually once you go off dialysis you only live for a couple of weeks my dad lived for eight months after he went off dialysis before he died so um they would always be astounded at how long he lived um while not being on dialysis well anyway we'll talk more about that later okay so here's how all of that is going to work it's a beautiful thing so stuff that's going to get through is going to go through the um filtration slits I mean not the filtration sets the pores the fenestrations so here are the fenestrations the stuff's going to pass through whatever can pass through this basement membrane and the filtration diaphragm the slip diaphragm then it's going to go through the filtration slits and then come out as filtrate and so this is in the everything over here is in the blood and then this is what's in the capsule in the capsular space okay so this is also another good thing to see oh look at that filtrate includes water glucose amino acids ions urea some hormones vitamins B and C ketones and very small amounts of protein all right so let's talk about what does get formed in filtration so what's infiltrate well first of all 180 liters of filtrator produced today hold up I only have 5.25 liters of blood so what does that mean that means that I filter my blood 35 times 35 to 36 times in a day I see my plasma so my my nephrons see my plasma my glomeruli see my plasma all 5.25 liters of my blood 35 to 36 times in a day okay then we filter and we're going to produce every minute we're going to produce 125 milliliters of filtrate every single minute out of our blood so every minute I'm going to take 125 milliliters out of my blood but then I'm going to return 99 of what I took out of my blood I'm going to return back to my bloodstream so that means I'm only going to take out one milliliter well 1.25 milliliters um in a minute which is going to add up to one and a half liters per day because that's how much how much urine that we make so what is it filtered plasma with solutes and some protein in there hot in the capsular space funnel to the proximal convoluted tubule materials that are not filtered stay in the blood go out through the corporate go out through the efferent arterial um and then any material that gets trapped in the basement membrane that gets to be eaten by the mesangial cells so is you it's like okay so I I don't drink juice anymore but when I drink orange juice um I Only Could Have pulp free well back in the 70s we didn't have pulp free orange juice we just had orange juice and so we had to have a strainer so I had a tea strainer that my mom would use to make me orange juice in the morning and so you know you're gonna pour the orange juice through and you're going to leave the pulp behind but what do you have to do with the strainer you just can't keep pouring the orange juice through that you have to rinse out the pulp and so that's what the mesangel cells are going to do essentially is rinse out that basement membrane from anything that got trapped in there so that it doesn't plug up the filtration all right so what gets filtered small substances water glucose amino acids ions okay not filtered not filtered at all formed elements large proteins large proteins namely albumin and antibodies okay those things finding proteins all that stuff that's not going to get filtered limited filtration depends on the size of the proteins usually black from filtration either due to their size or their negative charge which will be repelled by that slit diaphragm all right so how do we get this stuff out in the first place well we've talked about this already we've already done hydrostatic pressure now we're just saying it's the hydrostatic pressure of the glomerulus of this capillary bed so blood pressure in the glomerium so I always remember glomerulus is a ball of capillaries capillaries all right so it pushes his blood pressure so remember hydrostatic pressure pushes it out pushes out the water and the solutes goes into capsular space now we do have a higher than other blood pressure in systemic capillaries the blood pressure in the um in the glomerulus is right around six of the hydrostatic pressure is right around 60 millimeters of mercury typically in irregular blood or a regular capillary bed the hydrostatic pressure is around 37. so it's much higher it's almost double what the blood pressure is now why well because I'm pushing out lots of stuff I try I need a lot of hydrostatic pressure to push the filtrate out um so how do I create that large amount of pressure well it's all about the diameter of the afferent efferent arterials so we take the large diameter this is how I always draw it okay so here's my Affair and arterial now remember with blood pressure we talked about how blood pressure was due to the constriction of the arterials right the vascular smooth muscle Contracting and causing vasoconstriction well guess what capillaries do not have any smooth muscle in them so how are we going to increase the pressure in a cap in a capillary we have to increase blood flow so the more blood that we can get into a capillary the greater the hydrostatic pressure is going to be so how do I deliver a large amount of blood to this capillary bed well by having a big afferent arterial which is also short so large diameter right so the large diameter of the afferent arterial delivers a large amount of blood to the glomerulus therefore creating the hydrostatic pressure that you need now leaving so coming out of the um of the glomerulus is the efferent arterial the efferent arterial diameter is smaller than the afferent arterial therefore the blood's going to back up in the glomerulus and kind of pool around and again create that back pressure and that height that higher hydrostatic pressure that is required for filtration so remember large diameter of the afferent arterial small diameter of the efferent arterial creates a higher glomerular hydrostatic pressure than what you would have an irregular capillary vet then we need we don't want 60 millimeters of mercury worth of fluid to come out I don't want that much I need to oppose that fluid and so I have two pressures two Starling pressures that are going to oppose hydrostatic pressure of the glomerulus one is osmotic pressure we know that already what creates osmotic pressure the dissolved solutes plasma proteins albumin That Remains and whoops it remains in the glomerulus okay it opposed filtration by drawing fluid back into the glomerulus capsular hydrostatic pressure so now this is another hydrostatic pressure but that's generated due to the filtrate that just got pushed out in the capsule so now that I have a bunch and it doesn't flow as soon as it leaves the capsule I mean leaves the glomerulus it doesn't flow right away it collects in the capsule and as it collects in the calf capsule capsule as it collects in the capsule wow that hurt um it stops additional fluid from coming out or impedes it doesn't stop it just slows fluid coming out so what you get then are my two opposing forces that are blocking um hydrostatic pressure from forcing the filtrate out so it says if the pressure so now we need to determine net filtration pressure what is going to happen is stuff going to come out is stuff going to go in are they going to cancel each other out what is going to happen so if the pressure's promoting filtration are greater than the pressure is opposing then we get net filtration pressure we get more filtration than we have reabsorption so here is my hydrostatic pressure at 60. my osmotic pressure is usually right around 32 of Michael maryles sometimes it's 26 it depends on what book you're looking at um and then a hydrostatic pressure of the capsule of 18 these two numbers usually don't change this is going to change and this is going to change base it change based on um uh uh what your systemic blood pressure is so systemic blood pressure um effects ultimately what your um glomerular hydrostatic pressure is going to be so then if we add 32 and 18 we get 50 so 60 minus 50 is 10. so this is really so this is the force um of filtration because we're gonna get those opposing forces no matter what and like I said they're right around 32 and 18 all the time I usually go 26 and 15 but whatever it doesn't matter um I'll give you what the forces are if you need to have them on a test and um as long as that filtration number is always positive that filtration pressure is always positive and bigger than 10 then you will get filtration happening so this picture just shows how what's going on so here's this 60 out 32 back in the 18 back in So net filtration pressure is that 10 millimeters of mercury out into the distal convolent tubule nope proximal convoluted tubule all right so with a net filtration pressure of 10 of about whoops oh goodness 10 millimeters of mercury what does that do well that gives me what's known as my glomerular filtration rate so that's the rate at which filtrate is formed and one usually do it per minute okay so my GFR number that I need to know is 120 or that I need to maintain now that I need to know well yeah you need to know it but this is what my body's trying to maintain this is homeostasis for my kidneys if I produce 125 milliliters of filtrate every minute that sum total of my nephrons so if I took all of the filtrate from all of my glomerular capsules and dumped it into a container it would be 125 milliliters produced every minute okay now if I increase my net filtration pressure so we're going to look at how do I regulate GFR how do I stay at um 125 milliliters a minute if there are there's a chance that my systemic blood pressure is going to be changing because there is so what if I stand up what if I run what if I sit down but if I lay down what if I vomit what if I urinate what if I sweat all of those factors are going to affect my systemic blood pressure and those will then in turn affect my hydrostatic pressure and that in turn will affect what my glomerular filtration rate is so how much filtrate will I actually produce so if I were to increase filtration pressure either by sympathetic stimulation and we'll get into all of this in the uh maybe in the next video we'll see um so either through some sympathetic stimulation or increasing blood volume okay those things will increase my net filtration pressure um that'll increase my GFR so now I push in more fluid through so I push more fluid through that means more solutes and water are going to stay within the fluid they're not going to be reabsorbed not reabsorbed because because oops filtrate moves to quickly all right I'm gonna later on kind of as a culminating thing I'll put in this little clip it's actually both of them so Lucy and fo ol just in case you've seen either one of these Lucy and ethyl in the Chocolate Factory or yes my 90s children or my 2000s children um Drake and Josh at the sushi Factory all right both of those are examples of what happens if your blood pressure your systemic blood pressure is too high you'll get too high of a net filtration pressure your GFR will be too high you'll be shooting that stuff through your through your uh proximal convoluted tubule or your whole tubule and you can't reabsorb them and you're going to lose out really good stuff out in your urine we don't want that okay so like I just said it you're going to lose stuff in your urine and it's going to decrease filtrate reabsorption that's bad so do we have to tightly regulate GFR you better believe it I can't even tell you how tightly we regulate GFR so that will help our kidney control urine production based on physiological physiological conditions so like I I just went through those things right I said I drink too much water I don't drink enough water my level of hydration maybe I have diarrhea maybe I have vomiting maybe I'm out working outside where it's really hot and I'm sweating maybe I'm being chased by a Rottweiler I'm sympathetic stimulation all of that okay will affect how your kidney will um will filter your blood or produce your filtrate so we have these processes that will be able to counteract all of that happening so what are the most important things that will affect GFR the diameter of the afferent arterial okay so aluminal diameter of the afferent arterial and the surface area of the filtration membrane in other words how much um uh uh surface area I just said that how much of my glomerular walls are open for filtration so let me just tell you really quickly so those mesangel cells that we looked at that are between that are all between the capillaries so they're contractile and they have the ability that if I want to reduce my filtration fraction so I don't want as much blood being filtered if we contract those mesangial cells we pull in the glomerulus together so that I have less surface area for absorption and therefore less filtrate will be formed but if I'm not forming enough filtrate my mesangial cells will relax I'll open up that glomerulus and then I will be able to filter from more surface area of the glomerulus more sides of the capillary all right so um our we have the ability to regulate like tightly regulate glomerular filtration and what we're going to do is mostly intrinsic controls so this is where the kidney is going to adjust its um GFR at each nephron okay so this is at each nephron okay then um if that's not going to work if that does not reduce or increase GFR adequately then we can go out and affect systemic uh blood pressure okay so systemic blood pressure is going to be regulated from out in the out in the body and not at the kidney level so for example if my blood pressure is too low sympathetic stimulation vasoconstrict my epinephrine and norepinephrine bind to those alpha-1 adrenergic receptors and cause vasoconstriction and now my pressure will go up okay so extrinsic controls happen outside the kidney intrinsic controls are going to be at the nephron level so if we go to this this is probably the best thing ever that you can take a look at for um how do we know how to increase GFR I this nothing's better than this so but here's the here's the qualifier on this this is only this this table right here this concept map this is only for increasing GFR so this will these things only take place when we have low blood pressure in the renal vessel so this is going to be less than 60 millimeters of mercury in the glomerulus what are we going to do okay so what are the first thing the absolute first thing because we are doing this second by second in the in the Affair or in the arterials in our body and so we're going to also do it in the afferent arterials in right here in the affair and arterials going to each glomerulus and that's this one right here okay the myogenic mechanism that is the first thing your kidneys are going to do they're going to take a look at the blood coming in they're going to look at the pressure coming in and if the pressure is not high enough we're going to because the the the walls of the of the afferent arterials are not going to be stretched so if you don't stretch an arterial wall it's going to vasodilate okay so no stretch in on the renal vascular smooth muscle blood vessels so what are we going to do we're going to vasodilate and that's going to increase so then we come down here and that's going to increase um net filtration pressure I mean it's ultimate mostly it's going to increase hydrostatic pressure glomerulus that will then increase net filtration pressure and increase GFR the second thing that we're going to do is to be low glomerular feedback and I'm going to go in the notes because there's a little bit more than what I can say just in this picture if that's not enough and so these two are intrinsic these are at the kidney as we said at the kidney okay the extrinsic is at the body or in the body whatever however you want to say that it will either be a hormonal mechanism that will involve hormones and sympathetic stimulation and neural controls with sympathetic stimulation as well so these are going to be three and four that are going to happen at the same time so I can't it's not we're going to go green and then we're going to go yellow we're going to do green yellow at the same time we will do this one first we will do myogenic mechanism first and then we will do tubular glomerular feedback second all right so I'm going to leave that at this point because we're going to get into some weeds here in just a little bit and I have to go babysit my grandson so I'm gonna go have fun for a little bit and when I get back we will talk about regulation of glomerular feedback bye for now get rid of that stop sharing okay