Osmoregulation and Excretion

Hi In this lesson will be talking about the excretory system and Osma regulation. Osma regulation is thehyperfix static mechanism that allows organisms to balance their solute concentration and deal with water loss. Now excretion is the process of eliminating waste from the body and will absolutely involve loss of salutes and water from the body, which is why Theo Excretory System is heavily involved with Osma regulation. But the excretory system has another important job, and that's getting rid of nitrogenous waste, which we'll talk about in just a moment Now. The excretory system is made up of a few components. The main part is the kidney. That's like the business end of the excretory system. That's, uh, this being shaped Oregon. You actually have to one on either side of your body, and it's going to filter blood plasma and form urine. But it's a job is so much more sophisticated than that will really get into the details in just a moment. Now the kidney is going thio. Are the kidneys going? Thio uh, give off hearing that will be transported to the bladder by the Your Attar's thes are going to be tubes. Basically that lead from the kidneys to the bladder, which is the storage organ for urine and you're in will be stored there until it is ready to be eliminated through the urethra, which is the opening to the environment. Now, here you can see an example of a fish trying to maintain its osmotic balance, you know, by drinking seawater and, you know, passing water and salutes in and out of its body and excreting salutes so that it can maintain and Oz osmotic balance in its body. Now, nitrogenous waste is bad because ammonia is super top toxic substance. And it's on Lee safe in the animal body. If it's heavily diluted. Uh, it's gonna form from the breakdown of proteins. Nucleic assets, right. They both have nitrogen in their structures. And those nitrogen, they're gonna be given off as ammonia. This is for some organisms, okay? Because they can just heavily dilute the ammonia and eliminate it that way. Here, you can actually see what ammonia looks like. It's just a nitrogen with some hydrogen attached to it. And, uh, you know, organisms that have plenty of water around them, for example, like tadpoles, they'll, you know, often eliminate there nitrogenous waste of pneumonia because water is very plentiful for them. So it z okay for them to waste a lot of water, diluting the ammonia because there's plenty more available for organisms that have less water available. Yuria tends to be a better choice in terms of eliminating nitrogenous waste. Now it consumes energy. To make Yuria, those organisms have to take their ammonia and convert it into Yuria. And as you can see, ammonia is one nitrogen. Yuria has to nitrogen ins and a carbon and oxygen. It's actually basically formed by combining ammonia and Co. Two, that Z sort of oversimplified version of how area is made. The difference is it's way less toxic than pneumonia. And it is, uh, it doesn't need to be as heavily diluted. It could be excreted with minimal water loss, which is super important for, for example, terrestrial animals like us. We excrete area because we don't have that endless supply of water, you know, like all around us, like a tadpole, for example, so we don't wanna waste is much water getting rid of our nitrogenous waste. Some organisms, like organisms that live in really dry climates like reptiles in a desert, for example, will actually go even further and choose to excrete there nitrogenous waste as uric acid. You can see the uric acid right here. Jump out of the way so my head's not blocking it. And as you can see, ammonia had one nitrogen. Yuri had to nitrogen and uric acid has four nitrogen, so it is a bigger molecule, but it gets rid of more nitrogen. It costs more energy to produce than area. It's Mawr energy intensive. However, it's basically insoluble, so it can be excreted with almost no water loss, which is why it would be the appropriate choice for a desert dwelling organism like a lizard, for example, where water is extremely scarce. Now, the basic point I'm trying to make is that the type of waste excreted by an organism is tied to things like its evolutionary history and its habitat and its level of osmotic stress. So, uh, you know, for example, um, some birds excrete, you know, most of their nitrogenous waste as uric acid. But ducks, for example, excrete some like almost half really is Yuria, and the rest is uric acid because, you know they live in water the water fowl. They have mawr water available to them. So it's not, you know, specie necessarily species specific. It really depends on a variety of factors, including habitat. Now the other point I'm trying to make is that there's a fitness trade off between how much energy it costs. Thio produce the particular molecule that will get rid of this nitrogenous waste and conserving water. Right? You know, you might be able to save a lot of water by making uric acid, but it might cost you more energy than you can afford to produce it. So perhaps Yuria, for example, would be the better choice for you. You know, thes air, just sort of the trade offs of using either strategy. Point is, nothing's perfect in biology. It's just about doing the best you can give in your conditions. So with that, let's flip the page

before we get into the nitty gritty of how the kidney works, I want to review some concepts surrounding osmosis and diffusion. So to start, let's go over a little terminology. A salute is a substance that's dissolved in a solution, and an electrolyte is a specific type of salute that, when it dissolves, will actually disassociate in tow ions. So, for example, we have salt here. This is just like table salt, and it will dissociate into a sodium ion and chloride ion in water. Now, when salutes dissolve in water, if they don't spread out evenly, they will form a concentration Grady in, which is basically a difference in concentration of a salute over some areas. So here you can see we have a high concentration on this side and a low concentration on this side. There's blue dots representing the solids. This means that we have a concentration Grady int across this area. Now what's gonna happen if we have a concentration radiant and nothing is blocking. The movement of these salutes is we're gonna have diffusion, which is the movement of molecules, or atoms from an area of high concentration to an area of low concentration and you can see that happening here. This is diffusion, and you can see we have a high concentration here. But the's salutes are going to diffuse and spread out evenly throughout this solution. No, if we have something blocking those salutes from moving, there won't be any diffusion of solids. As you can see here we have a U shaped tube and there is a higher concentration of salutes on, uh, this particular side and a lower concentration of salt. It's on this side, but there's a membrane separating the two sides of the tube so those salutes won't be able to pass through on either side, so they can't defuse to spread out evenly. But what's gonna happen is we're gonna have movement of water across that membrane or osmosis, and the water is going to move from the area of low solute concentration to the area of high solute concentration. And the result is going to be that the water will balance the solute concentrations on each side. So here we actually have a higher volume on this side now. But as you can see, the concentrations of the two sides here and here is the same and that is due to osmosis. And, uh, that membrane is displaying selective permeability. Right? That is that the ability of salutes to cross or the prevention of solids from crossing due to the presence or absence of transport proteins. So here there's no transport proteins on this membrane, this membrane here for those salutes, so they are not going to be able to cross its impermeable to them. Now there are terms to describe the concentrations of salutes of two solutions. We use the term Osma Larry T to talk about the concentration of a salute, and it's a measurement of moles of dissolved solute per leader. You don't really need to worry about units for this. I mean, this is biology, you know, We just want to kind of think about it in terms of, you know, qualitative terms like, uh, you know, something having ah, higher Osma clarity than something else. And there's actually specific terms to describe that. So if a solution has a higher Osma clarity than another solution, we say that it's hyper osmotic. So if the solution that this cell here is sitting in is hyper osmotic, just gonna write hyper water is going to leave the cell because this area outside the cell has a higher Osma Larry t meaning that water is going to want to move out of the cell into that area of higher solute concentration in order to try to balance the solute concentration between the two environments. And it's going to cause the selfish shrivel. So again, the term for that type of solution is hyper osmotic. Here we have an example of iso osmotic solution where the solution outside the cell and the site is all inside the cell are of the same Osma clarity. So the water is going to flow in and out, um, at the same rate, So there's gonna be no net change in the amount of liquid in the cell. Lastly, the hypo osmotic situation which you can see here, is going to be when thesis allude concentration in outside or Sorry, the Osma Larry T is lower outside, uh, the cell than inside the cell. And so water is going thio enter the cell to try Thio Balance those solid concentrations. So again ah, you know hyper is higher Asthma clarity Hypo is lower Osma clarity and eso is sama's similarity. Now there are kind of like to Osma regulatory strategies that you'll see organisms have their osmo conformers, which tend to be marine organisms that are mostly ISO osmotic with their environment. So these guys aren't going toe actively regulate their, uh, their internal Osma clarity. Instead, they're just going to let it be iso osmotic with their environment. And that's okay because these marine organisms, you know, they live in salty water that has a very high salt concentration. Um, and, uh, you know is high enough that it's similar to the concentration inside cells, which is fairly high, actually. Now Osma regulators take a more active approach. These air guys who are going to actively regulate their asthma later the similarity of their internal environment. Last thing. I want to mention one really kind of weird strategy that some organisms show called an hydro bios issue, which is a type of crypto bio sis. It's, uh, basically an adaptation that allows organisms to survive, like without any water. These organisms will basically dry out or desa Kate and can still survive for quite some time like that. And example of that is this little guy right here that's technical name is a tartar grade, though I like the common name for it, which is a water bear. And this water bear is all nice and happy and plump with water. But these guys contrive out and shrivel into basically like nothing and still live like that for quite some time. So pretty wild adaptation. Lots of organisms have developed different strategies to deal with water balance. So with that, let's flip the page.

transport across membranes can be broken down as passive transport and active transport. Passive transport is the movement of molecules or atoms across the membrane via electrochemical grading. So basically no ATP is going to be expended. Thio have these molecules our Adams move. They will move due to the natural Grady INTs that exist now. A special type of this passive transport is called facilitated diffusion, which is essentially a passive transport where these molecules move across the membrane using protein channels or carrier proteins. Protein channels air trans membrane proteins that form a poor through the membrane that allows specific molecules or ions to pass through. So here you can see we have these two different types of molecules, but Onley these they're gonna move through the poor because these channels are specific thio specific molecules or ions. Now there's a special type of channel you should be familiar with, called aqua por in, and this is a water channel. Now, water is a small enough molecule that it can diffuse through the membrane without any assistance. However, it doesn't diffuse through at the rate necessary to sustain living processes, so organisms use aqua parents to make three passage of water through membranes much, much more efficient. You know, it's it's actually amazing how much more efficient it is. If you look at the numbers now, carrier proteins are a little different than channel proteins. Channel proteins air just like, ah, hole that things can go through To get through the membrane. Carrier proteins have to actually carry a molecule through the membrane so they'll actually bind a molecule on one side, and then they'll change shape. And in that process, they'll actually carry the molecule through the membrane and ejected on the other side. Um, so it's not like a poor, it's it's different. It's almost like a you know, e. I would think of it as like a train moving through a tunnel or something, right, like the the molecule has to board a car, and then it moves through the membrane, and then it's released. Now active transport, unlike passive transport, consumes a teepee directly in order to move molecules or ions across the membrane. Now there's two types of active transport that we classify as primary, active transport and secondary active transport. Primary active transport directly hide relies is ATP to power protein pumps The most famous example of thes pumps is the sodium potassium pump that is used for, like everything. It's everywhere in the body. It's probably the most important pump for you to know. Sometimes it's called Seneca TPS, which is sort of an abbreviated name for it. Now, what this sodium potassium pump is going to do is move three sodium ions and two potassium ions in opposite directions across the membrane. Here, you can see an ACA tapas and action. What we have is these are our sodium ions and they're gonna get loaded up in here. The three of them are going to get ejected on the other side, and that is going thio require some ATP hydrology. Sis, thes potassium ions will get loaded up in here. This phosphate group will be ejected, causing a confirmation. I'll change that. Releases thes to sodium ions on the other side. You don't need to know the specifics of it. I just go through it because, you know, I think it z interesting and can't hurt to know these things. Now. Co transporters are gonna be a type of secondary active transport Secondary active transport is going to harness the potential energy created by pumps so it doesn't itself consume ATP in order to move things. But it uses the concentration Grady INTs set up by pumps that do consume a teepee in order to move substances across the membrane. Now, if you're thinking well, how is this any different from, like passive transport? If they're just both use ingredients? The differences in secondary active transport those Grady INTs have to be actively maintained by pumps. If you shut the pumps off, you would lose secondary active transport as well because they rely on the Grady INTs built by those pumps. So, in a sense, they're indirectly using the at Pia's. Well, now, co transporters are going to, uh, carry out secondary active transport by using one substance to move another substance. So they're gonna move one substance along. It's Grady int, and they're gonna use the energy from that to carry another substance against. It's creating, and this can work in two directions, actually jump out of the way here. So you're gonna have sim porters, which you're gonna move both substances in the same direction. So you can see here we have a sim porter. It's gonna take two things move one along its radiant and the other against its radiant but moving one thing along its radiant will provide the energy to carry the other, uh, molecule er, Adam. Through Now, anti porters are very similar in concept. The only difference is they are going to move the substances in opposite directions across the membrane. But it's the same idea. One substance moving along its Grady in is going to power the movement of another substance against its radiant. All right with that, let's flip the page.

the kidneys are the major organs of the excretory system, and they're heavily involved in Osma regulation. They actually have two layers. This outer layer we call the cortex and an inner layer known as the medulla. And it's this inner layer that's going to be the saltiest layer. Uh, and the kidney is basically mostly made up of these functional units called neh Franz. And these are tube structures that transport Phil Trait, which we'll talk about more in a moment. Uh, and these tube structure is gonna be surrounded by blood vessels now, net. Franz, they're gonna use, uh, the active transport of salutes to create salty environments that will help these, uh, net Franz and the kidneys re absorb lots of water from the fill trade. And as I said, there are two layers to the kidney. You have the cortex, which is the outer layer, and the medulla, which is the inner layer. And you actually will see two types of neh Franz Uh, in kidneys, you'll have what are called cortical neh Franz like cortex. And these are the most common type of Neff, Ron, and basically, uh, the tubules of these neh Franz just don't extend that deeply into the medulla. See, here's the boundary between the cortex and the medulla. Here is a nef, Ron. Jump out of the way and you can see that this Neff Ron Onley extends a little bit into the medulla. Whereas this other Neff Ron is a just imagine Loring Neff Ron, which is mostly responsible for maintaining that osmotic Grady in for re absorption. So, uh, the cortical net Franz are there to you know, uh, filter the filter it and create urine and re absorbed lots of stuff. The just image Larry Net Net Franz are not as common because their job is more of a support role. They're just there to make sure that this area stays super, super salty. And that's why they extend very deeply into the medulla as opposed to the shallow extension of the cortical neh, Franz. And hopefully you can see in this image that we're basically over here. We're looking at like a slice of this it almost as if you took, you know, a chunk out like that and zoomed in. That's what you'd see. And hopefully you can also see just how riddled with blood vessels the kidney is it's super infused with blood vessels and you'll see why momentarily, this is so important. So with that, let's actually go ahead and flip the page.

we're gonna break down. What happens in the nef run into four categories. First is filtration, and that's when water and small salutes will cross the epithelial membrane and form fill trait. This is gonna happen in a structure called the renal corpuscles, which is made of these two parts you see here the GLA Marylise or glue Meriel or capital Aries and Bowman's capsule. Basically, uh, the fluid in the blood is going to cross over from the GLA Marylise into Bowman's capsule and be filtered and form fill trait. When the liquid enters Bowman's capsule. It is then considered Phil trade, which is just a solution of water and small salutes like salts, sugars and amino acids, as well as nitrogenous waste. What you don't want to find infiltrate is big stuff, like proteins or even cells. That means that there is some damage in your kidneys, and that's really bad news. You know, you gotta get that taken care of right away. Point here, though, is that Phil Trait formation is not very selective. Lots of water and salutes will make it through into the fill trade, but that brings us to re absorption, which is the most important thing, then Ephron is doing basically valuable salutes like glucose and vitamins will get actively re absorbed from the fill trade into the blood. In addition, salts will be re absorbed and water will move passively by us. Moses to follow those salutes that air actively maintained. Now re absorption is highly selective and tightly regulated. So Phil Trait formation is not selective. Everything is going to get dumped into the fill trait. But Onley important and good stuff for the body will get re absorbed back from the fill traits. So you see how this is a mechanism for cleaning the fluids of the body as well, because you just push them all out into this contained area and then you selectively re absorb the stuff you want so you can get rid of like toxic things this way. Like for example, nitrogenous wastes. Now you'll also have secretion, see some wastes and salutes will actually be actively added back into the fill trait from the blood. So in a similar manner, thio the specificity of re absorption secretion allows the body to specifically rid itself of certain things which can not only get rid of toxins but also help the body maintain proper osmotic balance. So end of the day you're gonna excrete this Phil trait after everything has been re absorbed and various things have been secreted into it, you're gonna excrete it. You could see these guys right here doing a pee pee dance because they have to excrete it. Basically, at the end of the day, excretion is going to equal what you get from filtration. Plus what you get from secretion minus what is re absorbed. So through the what's actually excreted at the end of the day is going Thio, you know, be only a small amount of what goes through filtration because a lot of that is going to be re absorbed. And here you can see how those different, uh, components are broken down throughout the Ephron. This is a very simplified version of the Nef Ron, and with that, let's actually go ahead and flip the page

all of the fluid that's delivered to the Nef Ron comes from blood vessels, which is why there are so many blood vessels that proliferate the kidneys. Now, specifically, the nef Ron is going to have what are called these para tubular cap Hillary's that will surround them and specifically surround the portions known as a proximal and distal tubules. Now the portion of these para tubular cap Hillary's that surrounds what's called the loop of Henle E is known as the Vasari CTA. And here in our image of the Net, from jump out of the way, you can see our Voss erect a Hear those red tubes surrounding, uh, the loop of the Nef Ron or loop of Henley, this yellow U shaped structure here and then up here we have our para tubular cab blueberries that are surrounding the proximal and over here, the distal to Buell's point being that the kidneys job is to filter thief fluid in the blood, and so there's gotta be a lot of blood that makes it to the kidneys in order for it to be able to filter that. That's why there's so many blood vessels in the kidneys and surrounding the net. Franz, now the beginning of the net front because it really is easiest to think about these as like a linear path, even though they're actually just tubes. That air kind of all wound up around each other. We're going to think of it as a linear path, and the beginning is the renal corpus school, which you can see right here. This is our renal corpus cule. It's made of two components. The Gla Marylise, which is it's a great glum, this ball of capital Aries here. That's our gloomy realists, and that's going to provide the blood to be filtered. You can also see the gloomy realists right here, but I don't think it does it justice, because really, it's it's a ton of capital. Harry's in there now, surrounding the glam aerialists is Bowman's capsule. This structure that you see here that is Bowman's capsule and its job is to collect the fill trait as it flows out of the blood. So the fill trait is going to go from the GLA Marylise into Bowman's capsule, and filtration occurs, Um, you know, due to the blood pressure, actually, that will drive fluid into Bowman's capsule. It's It's literally the pressure from the heart that drives this process, and the renal corpus school is gonna kind of act like a sieve, you know, like a or like you could think of it as like a strainer for pasta or something. It's going toe filter stuff based on size, so big molecules or cells will not be allowed through Onley, small salutes and water. In fact, if you see big molecules or cells that can indicate damage to the renal corpus cule, and that's bad news now, because so much stuff makes it through this sieve. This filter a lot has to be reabsorbed, right? A ton of fluid is lost to the fill trade initially, but about 99% of the fill trait is going to be re absorbed before it's excreted. So it's you know it's going to minimize water loss, but it's also going to allow for selective re absorption. That's why the kidneys act really as a filter system for the body, because they, you know, they push a ton of fluid through these tubes and then Onley reabsorb the good stuff that they need. So with that, let's flip the page

after the fill trait is collected in Bowman's capsule, it's going to move into the proximal tubules. So here you can see the glow. Marylise Phil Trait is going to move this way, and the proximal tube. You'll has what's called a convoluted structure. Basically, it's like a spaghetti noodle all wrapped up, lots of twists and turns. And, uh, you know, coils. In order Thio maximize the amount of area it provides while minimizing the amount of volume it takes up common tactic and biology. Now it's going to transport Phil Trait from Bowman's capsule to the loop of Henle E because it is involved in re absorption. It has that convoluted structure, and it also has Micro Valli in Lumen, which, both of which are going to greatly expand the surface area of the proximal tube. You'll, which is important for re absorption. Right, so glucose, amino acids, salts and other salutes are gonna be re absorbed by active transport. You can actually see like a whole list of the stuff that's going to be re absorbed right here. It's a ton of stuff, and water is going to passively follow those salutes because both salutes and water or re absorbed together. The Osma clarity of the fill trait is not going to change from re absorption in the proximal convoluted tube you'll so the total volume will decrease because a ton of stuff is going to get re absorbed. But the Osma clarity will stay the same. And here in this figure, behind my head, you can see other areas of the other areas of the nef, Ron and what they will be re absorbing. Um, here you can see some stuff that will actually be secreted into the proximal convoluted tubules, those air secretions. Um, next, we're gonna move on to the loop of Henle E, which is this structure here. And then we'll make it to the distal convoluted tube you'll hear and finally to the collecting duct. And you can see that all of these structures are specialized for the re absorption or secretion of various materials. So with that, let's flip the page

the loop of Henley is massively important structure of the net front that not Onley, absorbs a lot of water and in salt, but also plays an important role in maintaining the osmotic Grady INTs of the kidney that are necessary for water and salt re absorption. Now the loop of Henle E connects the proximal tube you'll to the distal tube you'll and it goes in and out of the medulla. It kind of dips its loop into the medulla and then comes back out. And remember, depending on the depth to which the loop of Henle E enters the medulla. You know, you, uh, would classify in Effron is either cortical or Juckes. Tim Edgell earn Ephron, and the first part of Loop of Henley, the one that goes into the medulla that connects to the proximal convoluted tubules is known as the descending limb. And this is a thin portion, and it's permeable toe water and lots of water. Re absorption occurs here. This is going to cause the volume of the fill trait to decrease because it's losing lots of water. However, it's not re absorbing any salt Onley. Water is being re absorbed here that means that the solute concentration of the fill trait is going thio increase, so it's actually going to become a Mork concentrated Phil trait. The ascending limb has a thin section and a thick section, and basically within ephron, thin sections don't do active transport. Thick sections do active transport. That's the difference. You need a thicker tube, you'll in order to attach all those pumps and, you know, specialized structures to actively, um, transport molecules, whereas you want a thin structure when it's your mostly gonna be relying on passive transport. Because, remember, uh, the distance that something has to travel will affect its rate of diffusion. So the ascending limb starts off with passive transport in the thin section, and it's going to be re absorbing salt, and it's impermeable toe water on. Then the thick section will active actively re absorb salt and the whole the whole ascending limb is is impermeable to water, so Onley salutes will be reabsorbed. I'm saying salt, it's other salutes to It's just easier toe thio to just say salt. So, uh, here, because salutes air being re absorbed. But water is not. The volume won't change volumes going to stay the same, but we're diluting the fill trait because we're taking solids out. So the fill trait is concentrated in the descending limb and then diluted in the ascending limb because we're absorbing water on one side and salt on the other. Now, this actually is a special type of counter current exchange. We call a counter current multiplier system, which is basically a system that expends energy to create a strong concentration radiant that it's going to use for counter current exchange. The way this happens is the deeper you get into the medulla, the salt here, it iss water will flow out of the descending limb because of the osmotic Grady int created by the ascending limb. So this portion of the loop of Henley creates the Grady int necessary to re absorb water on this side. That's the counter current aspect to this, Um, because uhh just something to consider is that as the fill trait moves down the loop of Henle E, it gets more and more concentrated right, because it's going to lose water along the way because water is gonna be reabsorbed. But as the fill trait gets more and more concentrated, so does the osmotic radiant outside of the loop of Henle E. You know, that's the other aspect of this counter current system is that, you know, as as it requires a greater and greater Osma Larry T to re absorb the water. The medulla provides a saltier and saltier environment to accomplish that. So basically high solute concentrations, um, at the beginning of the ascending limb are what are going to drive solute transport. Because by the time the fill trait makes it here, it's going to be so super concentrated that when it moves into the ascending limb, where it's no longer permissible toe water and now permissible to salutes, the fill trait is going to be more concentrated, then the environment outside of it. And so it's going thio re absorb salt. Salt is going to move out of the fill trait into this super salty environment, and that's going to dilute the fill trait as it moves up the ascending limb. However, when it reaches this thick portion, it's like the Phil trait is to dilute, to be moved based on those osmotic radiance anymore. And that's why active transport is used in the last portion in order to keep re absorbing salt and maintain those osmotic radiance despite no longer being able to rely on passive transport. And finally, after that, you know long journey up and down the loop of Henle e Phil traits going to make it to the distal, convoluted tube you'll, which is almost the end of its journey. So let's flip the page.

the distal convoluted tubules connects the loop of Henley to the collecting duct, and it's going toe actively re absorb salutes and can also re absorb water. The collecting duct is the final tube UAL element, and it can re absorb water and Yuria. In fact, the region in the inner medulla of the collecting duct is permissible to Yuria, which helps to create that strong, osmotic Grady int inside the medulla. So just another way that, uh, the nef Ron uses, you know, simple concentration. Grady INTs in order. Thio, you know, maintain those osmotic and osmotic balances to help drive this whole process. Here you can see another legend of how the nef Ron is structured and what gets reabsorbed. Where, um, you know, I've basically tried to provide many different images that all kind of showed the same thing more or less so that, you know, hopefully one of them is one that you really like and is gonna be one that you want to refer back to you. It's the reason I'm providing all these different images, even though a lot of the information is redundant just to give you a Knop shin of a diagram Thio refer Thio. Now the fill trait that makes it through the collecting duct is ultimately going thio be excreted as urine. But before that happens, there's going to be some hormonal regulation. Uh, that's going to affect the distal, convoluted tube you'll and the collecting duct, and we're actually gonna talk about two hormonal systems here. The first is anti diuretic hormone, which sometimes called a th or vasopressin. Now I'm just gonna call it a T H. A. T H is a hormone secreted by the pituitary gland in response to high blood Osma clarity, meaning like high solute concentration in the blood. What it's going to do is cause the walls of the distal tube you'll and the collecting duct to become more permeable toe water. And it does this by adding aqua poor ins to the A pickle membrane. So here you can see a small model of that happening. I don't want you to worry about the details here. All I want you to notice is that we have a TH which is a hormone that's gonna move through the bloodstream, bind to receptor on a collecting ducts cell, and that's going to cause mawr aqua porn's, uh, to be integrated into the membrane to allow for mawr transport of water. And this is ultimately going to lead to a large increase in water re absorption right before it's lost his year. And right, this is sort of like the last place that we can really do. You re absorption and that water re absorption is going to lead to an increase in blood volume. But because we're on Lee re absorbing water, we're only increasing the re absorption of water and not increasing the re absorption of salutes. We're actually going to decrease our blood. Ah, similarities. That's why this is secreted in response to high blood, a similarity to lower the blood off similarity. And it also will help increase the blood volume. So this will also be mechanism involved in maintaining blood pressure, and you can see that it actually could get quite complicated. I don't want you to try to memorize this chart. Uh, really. I'm just putting here to illustrate how complex and interconnected the maintenance of the system the system is. So with that, let's flip the page and talk about our last hormonal system involved with kidneys

Okay, everyone, in this lesson, we're going to be talking about the Rinnan angiotensin al Dossary own system that is utilized to regulate your blood pressure and your blood volume. Okay, so the Renan Angiotensin al Dust Arone system has an incredibly long name, so we usually don't call it by that name. We usually call it the wrasse system or simply wrasse. And like I said, it's going to control your blood volume. And it's going to do this by increasing your salt and water re absorption inside of your kidneys. But it's not that simple. Based on its name, you guys can tell it has a lot of components, and it's gonna have many different hormones that work together to raise that blood pressure and that blood volume now the loss of blood pressure or blood volume could be caused by many things. It could be caused by severe dehydration where you don't have enough water in your blood. It could be caused by a blood loss. Something like that. You need to make more blood. You need to have more water in your blood. This system is going to help you do that. So the very first cells we're going to talk about are gonna be these Juckes, Tegla, Mary ular cells in the Jackson glamorous color apparatus. That word is always hard for me to say. So these jacks, Tegla Mary ular cells are found in the Judge Jackson GLA Mary Alert apparatus. And from now on, I'm simply going to call them J G Cells because that is a common, shortened version of their names, since it is kind of difficult to say and these J G cells are going to be found in the kidney, but specifically they're going to be found in the blood vessels of be kidney. And what these cells are going to recognize is there going to recognize whenever the blood pressure or the blood volume drops? So they're going to recognize when the blood volume actually drops and they're going to release this protein called Renan. Renan is going to be the beginning of this entire process. Renan is going to be made by these jag cells inside of the kidneys. And then Renan is going to go on and start signaling all of these other hormones to begin. So it says here that Renan leads to the cleavage of angiotensin two angiotensin two. And actually, it's not that simple. There's angiotensin, but it can also be called angiotensin neogen. It's just a longer name for the same thing. And what's going to happen? I'll draw it down here, And Geo Tin Sina Jen is going to interact with Renan so these two are going to interact. Now Renan is made by the kidney cells. Those J G cells, and angiotensin again, is going to be made by your liver cells. But angiotensin again can't do anything in the form that it's in. But once it reacts with Renan, it's going to be transformed into angio Tin Tsin. One angiotensin one is going to be an active form of this angiotensin hormone. Angiotensin again is an active until interacts with Renan, and what Renan's going to do is it's actually going to cut part of the angiotensin again, molecule off and create angiotensin again one and then angiotensin again. One flows through the blood vessels and it's going to be converted to angio Tenzin to This is going to be the one I want you guys to remember, because it's going to do a whole bunch of really interesting things. So how is angiotensin two actually made angiotensin two is going to be made by these very specific enzymes called angio tension converting Enzymes, or ACE. So eight is going to do this to angiotensin one, and it's going to change it to angiotensin two. That is going to be the magical form. Angiotensin two is going to do a lot of things. Angiotensin two raises blood, blood pressure by vase Oh, constriction. And it's also going to stimulate the adrenal cortex to release al dost Arone. Now angiotensin two can also directly affect the kidneys and tell the kidneys to re absorb more water. And it can also tell the pituitary gland to secrete a D. H, the anti diuretic hormone, which is also going to make you re absorb more water inside of your kidneys. Okay, so angiotensin two is going to tell the adrenal cortex to create al Dostie. Arone Al Dossary is going to be the other hormone that is in this system. Aldo Cerone does some interesting things. Al Dossari is going to stimulate the distal tubules in the collecting duct of the kidney to re absorb more salt, and you may be thinking well to increase blood volume. We don't want salt. We want water. But remember, the process of osmosis water is going to flow towards the area of higher solute concentration. So if inside of your body has a higher solute concentration, you're going to re absorb mawr of that water from your urine and you're not going to release as much water. So this is actually a good thing. So the a D h anti diuretic hormone is going to make you re absorb more water. The old Austrian hormone is going to make you re absorb more salts which will inevitably also make you re absorb more water. So as you guys can see here, it says water follows the re absorption of salt leading to the increase of blood volume and blood pressure. That is great. So let me just make a little arrow. So you guys know that I was talking about that down there, So this is going to increase the blood volume, but you may be thinking, Oh, it's going to increase the salinity of the blood as well. It's actually not because Aldo Austrian also causes that water to come in. So it's not too salty or anything like that. Now, I also want you guys to know that this whole system can be triggered by the sympathetic nervous system as well, in case there's an emergency. If you go into fight or flight syndrome or or response, you will also stimulate this particular pathway, but you're going to stimulate it through a different means. And it's going to be this pituitary hormone, a C T. H. And it's going to stimulate the production of Valdosta Rhone, which is going to increase your blood pressure. And you may be thinking, Why do you want high blood pressure whenever you're in a fight or flight system? Well, you want this because it allows all of your organs to get all the blood that they need because it's increasing. Blood volume is ensuring that all of your organs, your muscles, your lungs that help you get away from the threat have the blood supply that they need. So you need to re absorb as much water as possible to create that perfect high blood volume and blood pressure. Okay, everyone, but the majority of the time we're going to use the Renan angiotensin l'd Austrian system or rest for whenever we have low blood volume, for whatever reason and generally not in the sympathetic nervous system. So now I have this really neat diagram that I think it's really helpful. This is basically just diagramming all of the stuff I just told you. Okay. All right. So it doesn't fit all perfectly. I will get out of the way in the second. The only thing that's really being cut off are going to be the lungs and the top word up there. But I will explain that. So let me scroll up a little bit so you guys can see everything. Okay, so where does this whole process start? Remember, the whole process is going to start whenever those kidneys realized that the blood volume is not high enough. So that's gonna be right here. The decrease in renal perfusion or there's not enough blood in the kidneys is going to cause those J G cells to realize that there's low blood volume and they're going to create Renan. So this is going to be the very first step. So they're going to create Renan, and then it's going to go this way. Okay, everyone. So what does ran into after that? Remember, after this, Renan is going to interact with the angiotensin again hormone that is made by the liver. And once it interacts with the angiotensin again hormone, it's going to create angiotensin one. And this is the second step in the pathway. And then the ace enzyme is going to turn angiotensin one into angiotensin two. And here's the ace enzyme up here. So now we have angiotensin two, and this is going to be the third step in the process. And remember, I told you that angiotensin two is a really important molecule because it does all of these really crazy cool things. So let me go out of the pictures so you guys can see the rest of it so you guys can see the angiotensin two is going to do a lot of things. Remember I told you that it's going to be important because it's going to constrict the blood vessels, which you're going to physically increase the blood pressure of that individual because those blood vessels are smaller there, constricted the blood pressure is going to go up. And remember, I also told you that it's going to cause thesis accretions of the A. D H hormone from the pituitary gland. And this is the anti diuretic hormone, and this is going to cause the increased absorption off water in the kidneys. Okay, everyone. Now it's also going to do even more. It's going to cause out Dos Trone to be secreted from the kidneys as well. And what Aldo Austin is going to do is, it's going to cause those salts to be re absorbed, which you guys concedes going on right here. Thes salts are being re absorbed into the kidneys, which means the water will follow and be re absorbed as well. And Guy's Remember, I also told you that angiotensin two is important for your sympathetic nervous system. It's going to play an important role in keeping your blood pressure high during emergency situations to ensure that you have enough blood volume to stimulate your running away from whatever it might be. OK, guys, Now, once the blood volume has gone back to normal, what is going to happen once it's gone back to normal? You guys can actually see down here this red line. This red line down here is going to be a negative feedback. And so once the kidneys realized that there is enough blood volume that it is back to normal and enough water has been re absorbed, they're going to send this negative signal back to the J G cells to tell them to stop producing Renan, which will stop the process. Which means that angiotensin again will no longer be turned into angiotensin one and eventually into two. And Al Dossari own will not be secreted. So this is on Lee going to be used whenever you don't have enough blood volume or your blood pressure is too low or you're in an emergency situation. But when you're not and your blood volume is perfectly fine, your kidney is being told to not make the Renan Hormone. Okay, everyone, I hope that was helpful. I know that these particular pathways can be rough, but it is really, really interesting how all of these different hormones actually worked together to control your blood volume. Okay, everyone, let's go on to our next lesson.