I said chapter 44 is all about osmoregulation and excretion how our kidneys work and how we are able to maintain fluidity and keep in eye on zand other small molecules and how we remove them we get too many of them so our systems whether you are human or any other sort of animal have a fluid environment surrounding the cells with the open circulatory system so we have the human lymph and with the closed circulatory systems we have the interstitial fluid and the blood and homeostasis needs to be in order we need to keep relatively constant concentrations of water and solutes to keep everything working correctly awesome regulation helps to regulate the solute concentrations and decide whether we need to lose or gain water and excretion helps us to remove excess water along with metabolites that our body no longer needs and other waste products so ozma regulation again is based on this relationship between solutes cells have to be balanced in terms of their water input we talked about this a lot when we talked about osmosis with isotonic and hypertonic and hypotonic cells osmolarity is focused on the solute concentration and that's going to determine which way the water is going to move if your solutions that you are looking at are eyes of osmotic and the water movement is going to be constant this both locations both solutions are fine but if they differ in osmolarity the one that is hypo is not ik that has way more water in it than it has the solute will have water move to the hyperosmotic the one that has too little water so there is an example more solutes water is going to move to the side with more solutes to try to balance things out maintain homeostasis there are ausma conformers and ozma regulators osmocon farmers are going to a pretty much just to your marine animals they maintain ISO osmotic conditions with their surroundings so their internal osmolarity is not going to change asthma regularity so our auto regulators will adjust their internal osmolarity to their water intake or to their to allow water to be lost or water to be gained depending on what type of osmotic environment they are in they are able to do this using a concentration gradient which requires a fair amount of energy but this also allows them to live in many different habitats a lot of animals are sent a hay line they can't deal with substantial changes in external osmolarity your hay line animals can this would be mostly your Osmo regulators but there are some Osmo conformers that can deal with osmotic shock more effectively and they too could live in environments that have a large ranges in this external osmolarity your marine animals we talked about the marine invertebrates are ozma conformers the marine vertebrates and there are some invertebrates are going to be Osmo regulators marine bony fishes are actually hypo osmotic to sea water and they along with desert animals will lose their water greatly as a result so they also gain salt either through diffusion or from their food so how do they make this work they drink lots of sea water and they excrete salts get to keep things in balance well freshwater animals are in a hypo osmotic environment so they are constantly taking water in so they want to try to minimize how much water they're taking in and not lose solutes so they do lose some salts from diffusion and they help to keep the water balance under control by excreting lots of urine the salts get replaced by foods and they get taken up through the gills so there's your marine fish and there's your freshwater fish you'll notice that in the marine fish they are taking in water from both seawater and ions from food they are able to excrete some of those ions from their gills and they're able to lose some of their water through the gills they do not release they do not excrete a lot of urine because again they are losing water constantly to their environment well in a freshwater fish they are gaining lots and lots and lots of water and so that's going to reduce your salt ions so they take them up through their gills they takes them up through their food and because they keep taking in water and they keep taking up ions they lose both through lots of urine in their kidneys and this is just a free wild one there are aquatic invertebrates that might exist in ponds that aren't there for an extended period of time and when that happens they will lose pretty much all of their body water and survive and in dormant state and then that is a tardigrade and you can see the hydrated and dehydrated forms and this is option is called or adaptations called an hydro bios's land animals have undergone adaptations to be able to minimize water loss the body coverings helped with this they helped prevent dehydration desert animals are able to get water or retain water through some anatomical features and also by living primarily at night they're able to maintain water balance land animals in general by eating moist food and producing water from cellular respiration if you are an asura regulator you have to use up energy to be able to maintain the homeostasis and within your cells to maintain your osmotic gradients how much energy you use up depends on the difference between the Oz molarity of your surroundings compared to yourselves how efficiently or and how easily water and solutes are able to move through the animal surface and how much energy is needed to move the solutes across your membrane so there's a lot of factors at play in determining how much energy is going to play a role remember that you have your interstitial fluid or you have your hemolymph that Bay's the cells and you have to regulate the solute content that's present there so that your cells are taking up only what they need transport epithelia are cells that are specialized just from moving solutes in certain directions kind of like we talked about with the arteries and the veins they are arranged in these pretty wild tubular networks and one example of them is in marine birds and their nasal glands and it helps them to get rid of excess sodium chloride okay so section two nitrogenous wastes reflect both its philosophy and its habitat what type of waste it makes and how much what can have pretty significant impacts on its water balance and so the nitrogenous breakdown products from proteins and nucleic acids are probably the most significant waste that animals have to deal with ammonia is pretty toxic and as a result some animals will convert it to less toxic compounds like urea or uric acid before they excrete it okay so aquatic animals are gonna leave it alone with ammonia we see that mammals some Nvidia's sharks and bony fishes are going to produce urea and then reptiles your birds your insects your land snails are gonna make uric acid so why do we make different types again toxicity energy costs are gonna play a role the animals that are able to escrita nitrogenous waste directly as ammonia need water and that works great for your aquatic mammals they can release it across their whole body surface or through the gills mammals livers and adult in fib Ian's tend to convert it into ammonia into urea and then the circulation sister Q Latorre system takes the urea to the kidneys where is able to escrita it with less water than the ammonia would need but this is an energetically expensive process so you've got to have the energy and make happen we talked about the particular organisms that are going to make your uric acid it is pre non-toxic it actually comes out more like a pace because it does not result in a lot of water being used up to do it it does not dissolve in water but it does require more energy so factors are gonna play a role in what wastes are excreted will depend on their evolutionary history their habitat aka how much water's around the environment of the animal egg and then keep in mind that this night the amount of waste you have will influence directly the energy that the animal will need to expend so regardless of what type of animal you are the excretory systems can have a range of setups they are used again to regulate that solute movement between your internal fluids and the external environment that animals living in if we're focused on urine most are able to produce it by refining a filter it from your body fluids and there's four main functions that we see in our excretory systems the filtration where we have filtered those body fluids reabsorption where we take back we reclaim solutes that are needed secretion where we add substances that are not essential wastes non-essential solutes from the body fluids to it and then excreting after the filtrate has been processed and has nitrogenous waste releasing that from the body okay lots of tubules are typically involved this is just a general setup of what you would see in excretory systems within an animal so if we could look at a proton of Phrygia a planaria we see that proton of Phrygians are Oh dead end tubules which are connected to external openings and they are able to excrete dilute fluids so they help maintain osmolarity within the planaria men enough Rydia are found in earthworms each segment has one of these they consist of tubules that collects eleven fluid and they are able to produce urine now the Hickey and tubules are found in insects they are able to remove nitrogenous waste from hema live and produce uric acid and then we have our kidneys the beans shape about ten centimeter long organs that have lots of non cemented tubules that work with the dense capillary network they are able to function in vertebrate excretion and ozma regulation blood enters via the renal artery and then it exits via the renal vein from every heartbeat approximately 20% of blood is pumped to your kidneys your kidneys have around 1,100 to 1,200 liters of blood flow through them daily and the nephrons in the kidneys process 180 liters of filtrate each day and then whatever is not excreted returns back to the blood the urine leaves the kidneys through your readers and drains into bladders which then leaves through the urethra okay we're gonna spend a lot more time on the structure of the kidney and the nephrons that make up the kidney nephrons are your kidneys functional unit each nephron will consist of a renal tubular and a renal corpsicle which is just a bunch of capillaries that have a parent arterial that's coming from the renal artery so where they get their blood the renal corpsicle again is just a bunch of capillaries it's kind of rounded it's called a gwamorous and it's covered by the Bowman's capsule the capillaries when they leave the glomerular illus can't say that we're saved my life form an efferent arterial then there's this thing called a BAE's erecta which is a capillary system which you're going to see that basically surrounds and intermingles within the loop of Henle and then from the capsule we also have the renal tubules so there are two main types of nephrons and this is again where we separate all those metabolites and the ions and water and other small molecules from our blood we have cortical nephrons and we have juxta medullary nephrons the cortical nephrons make up the vast majority of the nephrons we find in our kidneys the biggest difference between them if you notice is that the juxta medullary nephrons have much longer loops of Henle and so they were able to go further into the renal medulla so you can see in this particular picture the Vasa recta you can see the arteries and the veins you can see the Bowman's capsule the glomerulus and we're gonna talk about the proximal tubules and the descending and ascending limb of the loop Henley and the collecting duct as we continue on so there's a stepwise process in which blood filtrate our blood is filtered in the nephrons it's going to move from the gamba rose globular us into the lumen of the Bowman's capsule and then it will move through the proximal tubules a loop of Henle there's a descending and a sending a distal tubules and then it will move down through the collecting duct so that it can be prepared for excretion so we're going to look at each of those one at a time you have a cortex which is found towards the outside of the nephron and then you have your medulla which has an inner and outer portion the proximal tubular is found in the cortex it changes not just the volume of your filtrate and but also its composition the osmolarity of the blood filtrate that's present here stays relatively constant so we absorb ions and water our sorry in this tube you'll ions and water and other nutrients are reabsorbed back into the blood or into the interstitial fluid and then taken away and we also have toxic materials that are added to this filtrate so things are becoming more concentrated but we are not and we are losing both water and we are losing both ions but the osmolarity is remaining relatively constant and the descending limb of the loop of Henle is where we start to see some changes this limb extends from the cortex into the outer and inner medulla only water is able to leave in this part of the loop of Henle the aquaporin proteins that we talked about before allow more reabsorption of water into that interstitial fluid and that is able to be done passively because interstitial fluid is hyperosmotic to the filtrate which is moving through the loop of Henle so all said and done as it moves through the filtrate is becoming more concentrated there's more particles present compared to the water when we move back up into the a sending limb of the loop of Henle we're moving from the medulla to the cortex it's at this point that the loop of Henle is permeable just to salt and other small molecules that water has to stay put so now we're working against the Osmo clarity of the interstitial fluid there are two regions for this loop of Henle the thin region is where salt mousse passively the thickest where energy has to be expended because we're using a concentration gradient to move NaCl out so as we do this our filtrate is becoming more dilute since we're losing the ions that are present in it within the distal tubules molarity of the filtrate remains pretty constant there's both secretion and reabsorption occurring but it's pretty specific as to what takes place this is in the cortex we have potassium and hydrogen ions that are secreted into the filtrate and then we have salts and bicarbonate ions that are reabsorbed and some water is passively recaptured as well both in the proximal and in the distal the ion movements help to kind of help with pH regulation the collecting duct takes what we have now of our filtrate and helps to move it from the cortex through the medulla to the renal pelvis it takes advantage of the transport epithelium that are present in the nephron to help to process the filtrate into urine it's able to reabsorb any remaining solutes in it will produce a urine that is hyperosmotic to your body fluids depending on your body's needs with volume and pressure it can also play a role as to how dilute or how concentrated that urine is so here is a picture step by step of what's kind of taking place so you can see the red arrows are showing you active transport the blue arrows are showing you passive transport we talked about how both water and ions and molecules can leave in the proximal tubules and the descending loop of Henle only water is able to leave passively and the ascending loop of Henle we see that salt is able to leave with passively and actively in the distal tubules we have selective ions and molecules being able to move in and out of the filtrate and then the collecting deck we have salt leaving actively we have water leaving passively and we will talk a little bit about how some urea will also leave and what determines what's going to be left in your blood it's controlled by three processes filtration secretion reabsorption through filtration the fluid is forced by blood pressure from the Columbia rust into the lumen and secretion the filtrate gets joined by substances and the interstitial fluid like plasma and then reabsorption is taking back materials that can be used by the body small molecule sugars vitamins water and organic nutrients things Abadi needs at that particular time being able to conserve water is a very important to restaurant a ssin since you're not living in the water we are producing hyperosmotic urine and we're able to do this because of the energy the body decides to use towards this to transport cell use against their concentration gradients the two solutes that play the biggest role in determining the osmolarity are your salt urea so we talked about in the so the two solute models looking at what's happening with those two particular substances we talked about how in the proximal tibial the osmolarity remains roughly the same because you're losing both salt and water and the descending because you're losing water your osmolarity is going to increase pretty substantially up until it's always going to be basically continue to lose water until it reaches the osmolarity of the surrounding interstitial fluid and the ascending loop of Henle we are losing salts as we're not losing water to reduce that osmolarity and then the distal tubulin we talked about how it remains constant and then the collecting duct is going to vary depending on what the needs are other body why are we able to do this this is a counter-current multiplier system with the loop of Henle it helps to keep the salt concentration in the Kitty's interior pretty high we talked about those phase phase of Vasa recta vessels bloods moving in opposite directions because in theory this wouldn't work because you've got again everything wants to reach osmosis so how the heck are you able to get the kidney and the specifically the loop of Henle but it's needs and not have water move into the kidneys interior so those the Vasa recta veins are able or the capillaries are able to get the kidney its nutrients and don't interfere with the gradients specifically it just allows the filtrate to use active transport to move the salt against its concentration gradient so in the collecting ducts salts not going to be able to leave but only what water can so this will help to generate either dilute or concentrated filtrate we do see some urea leave this also helps with osmolarity as it's adding to particles that are present in that interstitial fluid it does get recycled via the loop of Henle but because there's constant linkage there's always some urea there to help with that interstitial concentration so both the urea and the salt are able to make it possible for the kidney to make urine that is hyperosmotic to your blood and not have it take water from the blood or from the interstitial fluid elsewhere in the body but it's actually ISO osmotic to the inner medulla interstitial fluid so the kidneys osmolarity is going to be hyperosmotic to pretty much anywhere else fluid wise in the body so this is kind of showing you what's happening with osmolarity values I talked about them a little bit you can see it is starting out around 300 Emilio's Malhar and then as it continues to go down the descending loop of Henle it's matching up with the interstitial fluid osmolarity on the far right as it moves back up through ascending and it starts to lose salt the osmolarity diminishes and then as it goes down the collecting tube the water and the salt will and the urea will leave until the osmolarity of the urine the filtrate the processed filtrate is going to be either osmotic with the interstitial fluid within the kidney so nephrons are going to vary in different vertebrate classes based on what the odds word regulation needs are for that particular habitat of the animal so in mammals we talked about how there are two types of nephrons the cortical and the juxta medullary that's basically how we're able to conserve water the juxta medullary nephron goes deep down into medulla is going to cause innate a super concentration gradient so it's gonna be able to produce urine that is more hyperosmotic to your body fluids when you live in a dry environment you're gonna have longer loops of Henle to help have those osmotic osmotic gradients that are pretty steep well if you're in freshwater so you've got plenty of water available you aren't going to need as steep of an osmotic raiding your not going to use up as much energy to produce that urine and so your loops are gonna be fairly short birds and reptiles also have shorter loops of Henry Henley excuse me so you would think that they would have dilute urine but again they can serve their water by generating uric acid so they put their energy into making that form of of making those changes to ammonia to produce the uric acid there are some other reptiles that have only cortical nephrons but they are the ones that excrete their wastes as uric acid freshwater fishes amphibians freshwater fishes want to hold on to their salts and their distal tubules so they are able to escrito arge amounts of dilute urine via cilia and then amphibians have a similar kidney function but they conserve water when they are on land by taking in water or reabsorbing water from their bladders marine bony fishes are going to be hypo osmotic compared with their environment so they're going to be the ones that are losing water they have small glomeruli and their kidneys some of them don't have them at all so they don't filter a whole lot they want to hold on to as much water as they can they don't make a lot of urine why what their kidneys are able to do is to help get rid of ions that are found by them drinking the seawater those ions are secreted into the proximal tubules and then excreted through the urine hormones can play a role in how your kidneys are functioning and maintaining water balance and dealing with blood pressure changes so this bat can produce both dilute and concentrated urine depending on what type of urine is producing it's able to both reduce its body weight pretty quickly or ingest large amounts of protein and still able to meet its water needs so the urine osmolarity is regulated by both hormones and by the nervous system ADH also known as vasopressin antidiuretic hormone makes the collecting duct epithelium more willing to transport water into that interstitial fluid so if the blood osmolarity not the kidney osmolarity and not the container social fluid osmolarity but if the blood of molarity increases ADH will be released this helps to reabsorb water so it's going to make your urine more concentrated and eventually was that water moves into the blood is able to reduce the osmolarity of your blood when ADH binds to receptor molecules on the collecting duct epithelial cells it increases the number of aquaporin proteins which is what allows the water to move through if there's an ADH mutation this can cause severe dehydration you're not able to remove bring the water back in and it can cause diabetes insipidus alcohol is considered to be a diuretic because it prevents ADH from being released so again why would you have an increase in blood osmolarity maybe you went for a 5-mile run and you were sweating a ton and so as a result your blood has lost water and we need to take water back in Osmo receptors in the hypothalamus or going to cause ADH to be released from your pituitary gland your collecting duct that final stepped in your nephrons is going to allow water to move across it so that it can be moved into the interstitial fluid and be reabsorbed as a result of being reabsorbed it's going to help to readjust your blood blood osmolarity another more physical indicator of the dehydration is that you are thirsty so you can ingest water which will also help to reduce the blood osmolarity and get things back to a homeostatic level okay so going back to cell signaling that ADH hormone finds its receptor on the collecting duct cells it sends off that second messengers amp which causes vesicles to be formed that are from taking in water from the collecting duct and then they are able to move through those channels to allow to water to go back into the interstitial fluid of your kidney wrasse renin-angiotensin-aldosterone this also plays a role in homeostasis the one we just talked about with a eh is only dealing with osmolarity of your blood the Columbia loris has a way to recognize blood pressure changes and when there is a drop it will allow the juxtaglomerular apparatus JGA to release renin and Renan will lead to the formation of angiotensin ii angiotensin ii actually causes a physical change in your arterioles it constricts them so it causes the blood pressure to go up and as the blood pressure goes up the blood flow to the kidney is reduced and the reduction in that blood flow will cause aldosterone to be released aldosterone acts on the distal tubules of your nephrons and your collecting duct to take in more ions and more water that's going to help to increase your blood volume and as a result your blood pressure so again the first initial change so why would this happen again you've lost water from exercise dehydration you haven't had enough water or you've had some sort of injury that's resulted in blood loss so the blood pressure has dropped so when that is recognized the juxtaglomerular OS projects juxtaglomerular apparatus releases renin-angiotensin sent ten Finnigan a precursor to angiotensin 1 and 2 is released in the liver or is present from the liver rent an axon that to turn it into angiotensin one ace another enzyme acts on it to turn it into angiotensin 2 angiotensin 2 on its own is able to constrict those arterioles which physically causes a change in blood pressure Boyle's law and then angiotensin 2 is also chemically able to encourage the under drain of land to release aldosterone and that particular chemical absorbs both water and sodium so that's gonna cause your as molarity to stay a fairly constant but it's going to increase your blood volume and as you increase your blood volume that's gonna help get your pressure back up to so the decrease in blood pressure that's recognized at the by the juxtaglomerular apparatus is able to result in both a physical change with angiotensin ii in terms of constructing your arterioles and a chemical change with the production of aldosterone so both ADH in rafts will cause water reabsorption to take place but remember ADH is only dealing with osmolarity changes Rath is dealing with specific changes in blood volume a and P is able because you know we got to have the counter balance the negative feedback will oppose wrath and it's gonna be replaced so that we don't continue to take in water more than we need to and P is gonna be released in response to blood volume increasing or and as a result blood pressure increasing and we'll stop runnin from being released further