so if we thought that the gross anatomy of the respiratory system was simple this is going to even be simpler but the histology and the physiology is even more complicated than the respiratory system which is why it's um pushed later on in the term uh I have the opportunity of being at a conference where a researcher who had worked with um a very well-known medical physiologist by the name of gon was there and his the presenter's specialty was Nephrology or kidney function I remember thinking yes we're going to have some answers to some of these things that we've wondered about and I didn't go up and ask any questions but some some of my very SM smart colleagues did and I was really surprised that this researcher said most of the time his answer was well we really don't know which was sort of frustrating human kidney physiology uh is somewhat different from a lot of other species um it seems to be one of the areas in our evolutionary history that there have been some modifications it ties in with our high sweat gland density in our skin because both of them manage water uh so doing Nephrology on other animals uh doesn't necessarily tell us about human kidney physiology now there are lots of people who have kidney problems um but uh that doesn't mean that we really understand all the details so depending on your biological sex um you will have the same number of uh excuse me of urinary system organs you're going to have a total of six organs in general it's the typical pattern two kidneys two ERS a bladder and then a variable length urethra that's where the whole two sex things comes in um that's my dry humor it's not really humor it's just anatomical description um and so you know that really is the anatomy we don't we don't have a ton of uh detailed gross anatomy names of lots of different orans and so most of that detail will be at the um barely visible to microscopic level and then the physiology Anatomy can be pretty ferous it can especially yeah um so kidneys are located retrop parital so the little parital membrane is here this is the membrane now would this be the visceral perenium or the parial perenium that I'm putting the red line on remember the difference between visceral and parietal multip yeah so there's the lining of body walls and then there's the lining of individual organs lining of individual organs is visceral is the term that's used and then the the alternative lining the one that is not around an individual organ it goes around a body wall it's called a parial so the the membrane that I drew here was the prial perenium um this is the kidney what's this spleen is going to be more reddish it's actually I think it's off to the left here this is the spleen get a different I'll just do s that's the spleen notice the really dark reddish color due to all the blood you're on the right track what's up it is the pancreas yeah so this is the pancreas the pancreas goes across the abdomen um so anyways as part of development the kidneys are tucked in here and they are surrounded by fat and I think I mentioned that probably I mentioned that in lab with you guys that if someone loses a lot of fat then their kidneys can actually drop um because the fat is part of the connective tissue holding the kidneys in place okay let me clear off the so kidney filtration um is actually suppressed when we're in sympathetic mode and so these are little bar or these are Little P graphs of the amount of cardiac output and so remember we've been using 5 lers per minute as our standard for cardiac output and then this shows where the blood is going so at rest around 20% is going to muscles around 1350 is going to the digestive system um the cerebrum or the brain is around 700 notice the renal is 1,00 okay so about 22% when we're exercising really hard it should be no surprise that the muscles get a lot more blood flow question um yeah out of out of 5,000 milliliters milliliters yeah these are milliliters sorry okay um so they do the total in liters and then the the subtotals or the different parts in milliliters um notice that kidney or renal is going to drop down to around half of its prior value at rest 1,00 and then um with at exercise around 600 so that's almost half of what it was and then it goes from you know almost a quarter of blood flow when we're at rest to less than 5% okay when we're exercising and I think I told you a few little stories about this over the over the term kidneys nephro and renal nefro is the the individual unit that makes up the functioning of the kidney nefro the nefron is going to be the major thing that we're going to focus on this chapter because it's the thing that does the blood filtration and then yeah renal is referring to the overall name for the kidney just like when we're studying um the liver the term hip will be used to mean liver yeah you know that you know Anatomy when you know all five names for the same damn thing which um can be really frustrating and sometimes I forget that we've eduse certain terminology or the book uses certain terminology I'm often not always but often familiar with other terminology just because I've been at this for 35 years or so um and so bringing that up is actually a good thing it's good to make those connections between terms that either mean the same thing or May mean something slightly different from one another um so some of the stories that I've told you I talked about my first Circle the bay run I think and that um I didn't end up needing to pee even though early on I felt like I needed to and so there may actually be certainly there's suppression of blood flow to the kidney and less filtration there may be a small amount of ability for the urinary bladder to reabsorb some fluid um and then got to throw my son under the bus this was a long time ago I think I told you he was very active very sympathetic nervous system sort of kid and we' put him in a car seat or he'd have to sit and in 10 minutes he'd always have to go pee so that going from sympathetic push push push while he's awake to then uh being essentially forced to not move around would turn his kidneys on and all of a sudden he'd have to go to the bathroom okay now the kidneys do a lot of things but the most essential is removal of nitrogen waste okay that's the one that there really isn't another system that can back it up uh it's it is life or death and um so that includes ammonia now ammonia two ammonia just to show you this two ammonia plus what is going to equal Ura plus H2O I think I might have heard it what was it again carbon diox carbon dioxide so CO2 and you might remember that from when we were doing the metabolism Pathways that we needed both the the ammonia and the carbon dioxide and then we um make the Ura okay so uh once the Ura is formed then the kidneys can get rid of that what actually does this ammonia plus carbon dioxide reaction what it's our favorite guest organ this term the liver yeah so the liver and the kidney they really work together on this so when people have high ammonia in their blood it's primarily a liver problem um if they're having both ammonia and Ura building up then the kidneys are very much involved as well um uric acid comes from some of nitrogenous bases that make up DNA and RNA and so when we're breaking down DNA and RNA um this uric acid gets formed main reason why it's noteworthy is um in blood or body fluids that cool this will come out of solution and make uric acid crystals which are very very sharp and that's called having gout so gout is the accumulation of uric acid which then forms crystals which damages connective tissue including soft connective tissue and actually joint surfaces and so often people will end up with these enlarged joints due to the uric acid any idea which joints are most commonly impacted yeah the areas that get cold so often often toes when we're asleep okay sleep we don't have as much blood flow and that provides the warmth and so if we're trying to cool our body by sticking our feet on out then then the toes can uh cool down um can you think of a health condition that would be a bad combination to have along with um gout there's probably more than one I'm thinking of rods or hypothyroidism either of those would be a bad combo because they both have to do with not being able to produce or hold on to much body heat especially in the in the peripheral extremities and so that you know there'd be a lot of a lot of uric acid that could accumulate just because of the temperature okay creatinin is a byproduct um and I think I've briefly mentioned it certainly not emphasized it it's related to creatin okay so creatin phosphate is that really fast um ATP Source okay so when you're clicking away for three minutes as fast as you can um it's that first 10 seconds or so um there was a sprinter by the name of Carl Lewis who he wasn't super fast out of the blocks um but in the last 50 m of a 100 m or so he'd usually blow everyone away because and then they tested did muscle biopsies of him he had more creatinin um or excuse me creatine in his skeletal muscle than basically anyone else at that time and that I think was part of the movement to take creatin supplements um as a source of additional you know High burst energy so creatinine is related to that creatine and it ends up being deposited into the blood by skeletal muscle primarily um just because by mass skeletal muscle provides the majority of I think the heart can actually dump some creatinin in as well um interestingly the kidneys handle creatinin in a way that we can if we know the blood levels of creatinin and we we monitor the amount of creatinin in the urine we can get a good idea of how effective the kidneys are in filtering blood because blood flows through the kidneys it is then filtered um lots of stuff is reabsorbed but creatinin is not reabsorbed and so you can get this ratio and in fact I had a patient would have been I think my second year in practice and he knew that he had kidney problems he knew that he had hereditary kidney problems or was something called polycystic kidney disease um no one had done a uh kidney function test he didn't know what percent what percent his kidneys were fun F so we did what's called a creatinine clearance test um where you take a blood draw also take um I think 24-hour urine is best and then uh you can quantify the amount of creatinin that ends up in the urine and therefore how much kidney function if I remember right he had like 35% of predicted or something like that and um I think at that point he had did had not had a nephrologist as a specialist and I referred him onto a specialist I think within two years he was is able to get a kidney transplant and um do better so we have two basic regions of the gross anatomy of the kidney the cortex and the medulla and they do have different structures and different functions in them um we've used the term cortex before so like the cereal cortex what does that cortex name mean shell yeah so I heard a couple answers um outer shell or outer crust um those are as opposed to medulla which means more internal um structures so the cortex is the outer portion remember the adrenals we have a total of four adrenal glands usually two on the left two on the right one of them being or two of them being adrenal cortex and two of them being Adrenal medulla they're technically separate organs but in this case the the kidney cortex and the kidy medulla they're parts of the same organ okay so probably can't remember I may actually already have the line that's going to pop up here but I'll draw it right now so it's approximately right here where these arches of blood vessels are that separates the outer cortex from the inner medulla okay um just like the lungs have multiple levels of blood vessel branching um the kidneys do as well lots of blood vessel activity we're going to learn a few of the blood vessels but not all of them actually with lungs it was not just blood vessels but it was the bronchioles and the bronchi um that have many many levels of branching um one of the important structures in the medulla is called the renal pyramid and it is roughly pyramidal in shape when we just look at a slice of it it will look like sort of like a triangle um and it's some there's some specialized tu tubing in there that is filtering the taking the filtrate of blood and reabsorbing most of it most of it's going to go back into the bloodstream um but then concentrating the Ura and some of the other things that we're trying to get rid of and out at the very tip here right there this is the pill literally meaning little nipple of the pyramid and out of this n nipple I'm doing this for dramatic effect comes urine so it's little drips of urine that come out of the tips of the renal pyramid and then they flow into what are called minor koses which then converge together into major kaces which then come together into something called the renal pelvis so the renal pelvis is I guess I label it a little bit too hi the renal pelvis is important because this is the largest area uh in the tubing of of the urinary system essentially and so when kidney stones form they have a tendency to form there and then when they break loose they're trying to go through smaller tubing than where they were formed and that's where a lot of the trauma and the intense pain comes from is you're trying to take some you know sharp stones that formed in a larger area of tubing and have forced them as they go down force them through smaller tubing um one of great pains um let's see was it last week or the week before I mentioned one of the really painful things pancreatic pancreatitis is one of the great pains people can have passing kidney stones cancer um child birth child birth yeah um so let's see any had this experience and want willing to share it was horrible I thought I was going to die yeah and yeah did you do anything to try and prevent future ones orink yeah just drink more water okay some people will put like a little lemon a little bit of acid acid does have a tendency to um help dissolve but it's not a major effect the main thing is just plenty of water um this was some time ago now this would have been probably over 10 years ago um my hiking partner and the lady that I was dating was actually hiking the Rogue River Trail and it was a Thursday night I was teaching lab and she had a hiking partner and she and my uh girlfriend was throwing up and in really in bad shape and so uh any of you been to Mariel the little town of Mariel uh well you go past remote to get there way south of powers um and so I she had GPS coordinates she sent me and um so I left you know as soon as I could after lab I got a couple Maps I finally got to her at 11:00 at night the reason why I needed to go is her hiking buddy had left to try and go get the car um because then you could drive around and pick her up Mariel does have Road access there's a little summer camp thing there anyways so Port Tracy's uh throwing up um over and over again we got she wanted me to go find the car where her hiking buddy was her hiking buddy they' already done like 20 miles that day and her hiking buddy was going to do another 30 miles to try and get to the car so we were sort of worried about her and even though it was spring I got stuck in the snow in a four-wheel dive truck three times and like we had to dig our I had no shovel or anything we had to dig ourselves out and um so finally I'm like I can't I can't go over you don't think of the coastal mountains as having a lot of snow but they did that spring um and so we came back to KZ Bay we got into town at like 6 and I had an 8: a.m. lecture and so I'm like I'm not going to bed you know I won't wake up so I got a little bit done I think made some coffee and then went straight to lecture anyway so kidney stones are a big deal um she ended up oddly enough passing some of them while we were digging out of the snow probably more detail than you want to know um but yeah pretty incapacitating so I have held buckets for people vomiting due to passing kidney stones I've never had them okay so already talked a little bit about the amount of blood flow uh at rest that goes through the kidney um this is just an overall uh layout of the most important blood vessels of them thought that I had this labeled here of them I'm going to of course want you to know the renal artery and renal vein those are the arteries that come into and out of the kidney and then the other ones that we really need to know are the aparent arterial the peritubular capillary the vasera the eer arterial and the glomerulus so these um the glomerulus is a type of capillary that's supposed to be a c that's a really crummy C and then the peritubular capillaries are obviously capillaries and then the vaser reacta are capillaries so we've got three capillary beds out of the five vessels that I'm telling you about so there's an interesting pattern here where you've got the Glarus being a capillary bed an eent arterial and then the blood can go one of two ways and you've got another capillary bed we've actually only come across this two other times so far in our study of anatomy where you have a capillary bed another blood vessel and then another capillary bed and those patterns are actually a bit different it occurs in the um it occurs in the hypothalamus pituitary region and it occurs in the Digest Ive tract going to the liver so what are those circulatory systems called where you got capillary bed blood vessel another capillary bed yeah the portal portal circulation so the um hypothal um pituitary portal circulation and then the hepatic portal circulation this is not a portal circulation which is why I was being vague about blood vessel I didn't say artery or vein the other one's there's a vein a low pressure vein between the capillary beds and the idea of those um whether it be you know in the brain going to the pituitary gland or in the digestive track going to the liver is things are picked up carried through the portal vein and dropped off at the second capillary bed the opposite is happening here this is why the the epher arterial is not a portal vein the pressures are wrong and what's actually happening here is wrong so guess I'll use this at the glomerulus all sorts of fluid leaks out into the kidney tubing so there's kidney tubing that is not shown here and then it can be picked back up in the peritubular capillary or in the vasar recta a portal circulation a porter is someone or something that carries something from one location to another why is the epher arterial not called a portal vein it's called a epher arterial because it's not carrying anything special it's just got the leftover blood the fluids that are filtered from the Glarus they go in other tubing not a blood vessel and then they get picked up in these capillar so it's the opposite of a portal circulation um in that it's not a blood vessel carrying from one capillary bed to another I realize that this may seem like a little Nuance or it may not be super clear why I'm emphasizing this um but we'll we'll get back to this um when we're studying the tubing of the nefron um the tubing that carries the filtrate of blood these blood vessels are always nearby and they're not always drawn in and so you have to remember oh next to this tubing of the kidney are blood vessels capillaries in particular and so there's this exchange between the tubing that's microscopic here it's not it's not actually shown um on the kidney illustration here oh actually it is so they have drawn in the yellow here that so this is what sort of the general pattern of where nephrons would be down below here the AR um says arcu artery and vein but you have this little yellow drawn in nefron but you have to remember that right next to all of that tubing are capillaries and those capillaries they can allow for exchange of fluids and things in the fluids and I realize that that's probably sort of EG like okay he said some stuff but I don't really know what to do with it yet so we're going to start going through different levels of detail of the nefron the nephron there are somewhere around 500,000 or so nephrons in each kidney that's a very round number I could be off by 50% or so um and we're it's much more complicated than this but this is the most simple view that we have and so I'm going to just walk through the basic things that happen here and then we will take a break so we've got this apher arterial and this is unaltered blood just blood that is coming into the the kidney and it's going through smaller and smaller blood vessels and then it makes it to the first capillary bed called the glomerulus so the glomerulus is a capillary bed so what's it made out of simple squamous epithelium so that is one name in a good name someone else what's another name for simple squamous epithelial tissue of blood vessels starts with an E endothelium remember endothelium okay so we have filtration that occurs here so some of the fluid maybe around 20% or so of the fluid that's in the capillary bed actually leaves it could be 10% I don't know but it's a percentage uh will leave the uh glomerulus and then it gets picked up by this structure called the nefron and there's a particular part of the nefron that receives the glus fluid called the Reno cor pusle is one of the names for it so then this fluid called a filtrate it's not called urine yet it is migrating on down through this renal tubing but a lot of it's going to be reabsorbed so a lot of it's being reabsorbed here and this was actually going to use ATP okay it takes work to reabsorb it um in the very first section of this tubing about 60% of the fluid is going to be reabsorbed and at first that seems nonsensical it's like it's like first you take something put it in one spot then you take it and you put it back it's like why do that that seems like it's a waste of energy well the reason why that is done cut to the chase here is when you take a whole bunch of fluid out of the blood maybe one bit of it is something that you don't want it's bad it's Ura and the rest that's put back gets put back but you don't put back the thing that you're trying to get rid of so it's a way of concentrating the Ura okay so this re this filtration and then reabsorption is actually really important in concentrating the stuff you're trying to get rid of and to keep it in the um filtrate which will eventually become Ur um urine so that's reabsorption and then um there is some secretion some of you might be aware of certain people taking diuretics and there are diuretics that are considered potassium sparing versus non-p potassium sparing this is just if you have a someone that you know who takes diuretics or you've worked in medical practices that you know need to know this about patients um so pottassium is actually secreted in this phase three here and there are some diuretics that can alter potassium um secretion and so then people on those diuretics if it if it does more potassium secretion than normal they need to actually take a potassium supplement otherwise become deficient in potassium um so this is our most simple view of the Nephron the nephron is this yellow tubing and then all of these blood vessels are associated with the nephron and I want you to remember that anywhere you're along the nephron there are capillary beds right near it and there's the possibility of exchange between the nefron and the capillary bed so we'll take a break and then come back to this and we're going to start getting into more detail about how this works this was our first and simplest view of a nefron we're going to move on to more detailed anatomically correct views and there are actually four levels of detail so this is one we're going to go to level two one of the main things that is lost in the different levels uh after this is they don't draw in all the blood vessels you have to remember that there are always capillary beds right near the tubing of the nefron so they may have capillaries in some areas but they're not going to show it everywhere so sure enough they don't show they show blood vessels they just show the Glarus as a capillary they don't show capillary beds around all of the other tubing here so now we've got this structure called a nefron and what's happening if I can draw this in oops is blood is flowing in from this aparent arterial here into the glomerulus and then the glomerulus has holes they're technically called fenestrations you remember fenestrated capillaries so they've got capillaries with little holes in them and so a percentage of that fluid will leak out into what's either called Bowman's capsule or the nefron capsule and so even though it leaks out of the capillary there's this overall epithelial tissue surrounding it that will capture it and then it's going to start to flow down the nefron here so that's called the filtrate now we do have um a zoom in on some of the tissue so this outer glomular capsule it is well actually you tell me what does that tissue type look like right there yeah simple squamous epithelial tissue this isn't endothelium because it's not a blood vessel it's a capsule around some other blood vessels so then uh we zoom in actually on the glomerulus and um we do have simple squamous epithelial tissue called endothelium here it's very thin and it's the cells of the endothelium are are right there actually and there are little holes in there now oddly enough the holes in the endothelium are not the limiting size for things to filter through there's an additional cell that provides support to the endothelium and it's called a pooy it literally means foot cell a podiatrist is a you know someone who works on feet um probably not the best way to summarize their job but you get the idea and it's the the Poo site they have little toe likee appendages that interdigitate like this and they create filtration slits and it's the Poo site that actually creates the limiting space of what can leak out okay so it's what determines what can filter so then we look at the proximal convoluted tubule in the section that I now have the arrow going down where the filtration is occurring and we look at this tissue isue and we've got microvilli and we've got mitochondria what are microvilli used for why would why would epithelial cells have microvilli cat on things to what to catch on to things catch on to things so in what way yeah okay um so sort of like I shouldn't do this it's actually not like in in microbes so it's not it's not primarily about adhering it's mostly about increased surface area so if the micro are about increased surface area what's happening with that increased surface area AB absorption so increased surface area means more stuff can go through you've looked at filters like air filters they often have these folds or baffles and that additional surface area of the filter means that you can get more air through it similar idea for the microvilli so the microvilli all ow for reabsorption and we technically call it reabsorption first of all the the fluid was filtered out of the glomerulus and then we're going to reabsorb it by this cell and put it back into the blood vessels that are not shown here but they're right nearby okay and then there's also a lot of mitochondria why are there so many mitochondria in these proximal convoluted tubal epithelial cells the pumps and by the way most of these pumps they're not the pump that will not be named they are are sodium based pumps that also will escort a glucose or escort an amino acid or escort a variety of other nutrients with them and so it's it's sodium based and the sodium ends up uh driving a lot of the movement but it uses a ton of ATP so I've mentioned throughout the year that the brain is most dependent on oxygen the second most dependent organ that I know of in the in the body is the kidney and it's these cells in particular that have to have that oxygen to create the ATP to run the pumps to then reabsorb the fluid okay I am aware of a few cases where people have um had some sort of major surgery some usually cardiac type surgery and um they kept the brain well profused with blood but didn't keep the kidney well profused and the person essentially as they're recovering they found out that they got kidney failure due to that event that happened in the surgery so you got to keep both the brain profused with blood and oxygen and the kidneys profused with blood and oxygen during you know something like a surgical event um in order to not have organs fail okay so in fact this proximal convoluted tubul is going to reabsorb about 60% of the um fluid that is filtered at the Glarus and again that maybe seem like a waste first you dump it and then you put it back but 60% means that now the Ura is going to be over double its original concentration because the Ura is not reabsorbed okay so then we go to the next round of uh activity and there's a it's either called The nefron Loop or The Loop of Henley um using eponyms naming things after people is something that in general they're trying to get away from the problem is it's mostly probably the doctor's fault um doctors a lot of them in Prior Generations including my generation learned a lot of these eponym names and they want to essentially show off or that's the name that they know and they're either showing off or unwilling to learn the other not eponym names the descriptive names and so this is part of why you know that you know Anatomy when you know all five names for the same damn thing because you know people won't just transition on over to the descriptive Nam so instead of loop of hinley it be called The nefron Loop is the general descriptive term this NE nefron Loop if you're looking at what it does and you just look at the nefron loop it's not going to make any sense if you just zoom in guess I'll do purple you just zoom in right here and this is all you're looking at because what's going to happen is as this the filtrate is dropping down into the nefron loop or The Loop of pinley if you prefer water is going to leak out and that will concentrate the filtrate and then as the filtrate ascends the ascending limb everything except water is going to leak out and Ura and so it will dilute it and so it's like going one way it makes the filtrate do one thing and then going the other way going back up it does the exact opposite which makes it seem like it's a total waste of time it's not this is actually really important and the thing that's important is that it creates an overall concentration gradient so as we go deeper into the medulla the concentration of the fluid in the tubes and in the space between the tubes becomes much higher and that will be used by the collecting duct the whole purpose of the nefron loop is to create a concentration gradient that can be used by the collecting duct which is another tube that's nearby just giving you a heads up hopefully I remember just going okay I understand what the descending limb of the nefron loop does and what the ascending limb does and when I look at both of them some stuff's reabsorb but it completely puts things back the way that they were before it went through the loop so what's the point and the point only makes sense when you look at the collecting duct if right now you're like I don't know what he's saying that's totally fine I'm just giving you a little heads up that you can't just look at the ascending limb and the descending limb and figure out what's going on you have to look at ascending limb descending limb and the collecting duct in order to see any benefit in this nefron Loop question com yeah yeah and it's going into blood vessels that are doing something called countercurrent I don't know if you're familiar with countercurrent flow it's used in engineering situations it does some interesting stuff back in no there's not water going back in but the sodium and everything else other than Ura and water is taken out diluting the remaining filtrate so the total amount of filtrate keeps decreasing as you go through the tube but first of all you're concentrating the urine or it's not urine yet but the filtrate and then you're diluting it and it's like why concentrated if you're going to just dilute it again and the answer is it sets up the collecting duct here to be able to help us regul at um water reabsorption to help prevent us from becoming dehydrated it's the length and the level of function of this Loop of Henley and this uh collecting duct but primarily the loop of Henley that determines how concentrated of fluids we can drink and not become dehydrated if you're on out at Sea let's say I'm on out tuna fishing I go out in my kayak that I mentioned earlier it's 40 miles out I'm in genius mode right now I'm fishing and I dislocate my shoulder so I'm floating around delusional that maybe I might be able to win another thumb Olympics it's probably not going to happen and other stuff and I'm like I'm really thirsty should I drink the water it's right there WHYY make me to more thirsty unless if I would have a longer nefron Loop then I would be able to drink that and act get rid of the salt and reabsorb the water it has it it the length of the nefron loop camels would probably be able to drink salt water have you ever thought so here camels in a desert and they can really they have probably very concentrated urine I don't know that I've ever you know monitored camel urine limited opportunities to do so but they they can make very very concentrated urine why would camels make really concentrated urine what's the purpose of that yeah they're trying to hold on to water they need to hold on water hold on water hold on water and yet marine mammals also can drink salt water they don't have to go and find fresh water so if you've got a dolphin or a porpus or a walrus or a harbor seal or whatever they can just drink salt water have you thought about that that they don't have to go and find fresh water so we' got sort of two opposites camels completely the opposite of marine mammals how is it that they can do that they have longer nefron Loops I'm guessing that's my hypothesis have I actually seen gry whale kidneys no okay um but in general if you have a longer Loop you can create a big a higher concentration gradient which means that you can concentrate um the urine enough that you can pull the water out and keep from getting dehydrated okay more on this and this is why the kidney function in the urinary system is usually late in third term or halfway through third term of or in the semester system halfway through the second semester is the physiology is pretty detailed and there are these little nuances um we will do your analysis and do some stuff in lab and hopefully that will help with understanding how all this works okay so the main focus of this slide is actually that we have different cell types that make up different parts of the tubing and they're doing different functions so this this um descending l of the loop of Henley we've got these cells here is there much pumping of material going on based on what you see there remember we talked about cells and tissues that pump a lot of stuff across them this thin thin limb pumping much fluid no and yet I said that there is material moving so then what's moving it well the thick segment here which there is not a this segment right here which I don't know if you notice that they don't actually have a tissue sample of that they don't have what the cells look like if we were to look there we'd see that there's a fair bit of mitochondria so they're pumping sodium out of the filtrate along with other solutes and and um if you have we'll just call it salt water for right now if the filtrate is salt water and you're removing the salt what's happening to the salt water is it becoming more concentrated or less concentrated less concentrated and so they don't show that here they don't show that there are um little cells in this thick segment that are pulling sodium out and some other solutes and making the um the fil rate less concentrated okay so then and we'll get to this later I'm just giving you a heads up that what happens in the thick segment is what actually drives the activity in the thin segment and they're dumping it into the blood vessels that are not shown here we're going to have a whole little thing on the countercurrent flow when you have when you have two when you have two tubes and the fluid whether it be a gas or a liquid is Flowing one way in one tube and the other way in the other tube you can get different exchange than if you have parallel or concurrent flow and so this is used in engineering but it's been used by biology for longer and we're going to find out that um this allows for the concentration of the medulla okay and I realize that I'm not doing a good job of explaining this right now so just put a little bookmark there some we need to talk about some important and cool physiology in the nefron loop and in the collecting duct so then I told you that um we're going to add more detail we can now see that there are some additional blood vessels that weren't here before so all along all of the tubing we have these blood vessels Vasa recta Vasa refers to blood vessels recta means straight and so these are going along the nefron loop so anything that is uh coming out of the nefron loop can just jump right into the bloodstream except Ura Ura can't get into the bloodstream it's not allowed into the blood vessels because we're trying to keep it in the kidney and concentrate okay so cortical neurons look at their nefron Loop or their Loop of Henry Henley not Henry and then look at the juxa medular nefron which one has a longer Loop of Henley or nefron the jux medular nefron so even though they only make up about 15% of the nephrons they're the ones that can most effectively establish that concentration gradient they're the ones that determine how concentrated of fluid how concentrated soup you can have without the soup dehydrating you if you put too much salt in your soup you're going that fluid in there is going to overall be lost because you have to get rid of this excess salt okay so it's the even though they only make up 15% they're the determining Factor on how concentrated of fluid you can have I didn't actually use this case but one of the cases that a group of students wrote was based on a real life event of a fellow of course it was a young fella deciding instead of doing um using beer bong for beer he'd use it for soy sauce soy sauce is so concentrated in salt it actually killed him um and so it's quite a bit more concentrated than seawat and if you if you get that much salt in the form of sodium chloride into absorbed into the blood it can be fatal this is like based on a real event it's one of the cases that that a group uh wrote anyway so the JX medular nephrons are important um even though they're the smaller percentage