Transcript for:
Understanding the Urinary System

Hi this is Doctor Brown and this is going to be a lecture ... video for the urinary system. Here's the big picture of the chapter so I'll start with an ... overview of the kidney functions then move into the ... anatomy and histology of the kidneys. And then we'll start to get more into for the rest of the ... lecture talked about the physiology and there's three ... main parts to the physiology the first step is always ... something called glomerular filtration that's when you make ... your initial urine. Or what they call your filtrate. But that's not your final version of the year and there's ... two other processes that happens when they called ... reabsorption and secretion that can modify the urine ... further we'll talk about that. One of those things that your body needs to be able to do is ... it needs to be able to get rid of waste products that is that ... build up but at the same time control the amount of water in ... your body and your body able to do that through the ability ... to make either dilute or concentrated urine okay you ... know if your if your body is overloaded with water ... obviously you want to get rid of more water so that would ... be a situation when you make a very dilute urine to be very ... clear appearing you'd make a lot of urine right. On the other hand if you were say dehydrated you know ... your kidneys would still need to get rid of waste products ... but you wouldn't want to get rid of too much water so ... under those circumstances you would make a very ... concentrated urine in that you know that would be a urine ... where that would be very dark yellow or even maybe a little ... bit brownish and you wouldn't make much of. I will talk about how you can evaluate kidney function like ... in the hospital setting or clinically then we'll talk about ... some of the other parts of your urinary system urine ... Transportation storage elimination so here we're ... going to be talking about like your bladder as well as like ... the ureters would carry the urine from your kidneys to ... your bladder etcetera. Briefly discuss Waste Management in other body ... systems you know the main system that takes care of ... waste is your urinary system but there's some other ones ... that play a role and then briefly will mention ... development of the urinary system and aging in the ... urinary system. Alright let's talk about the overview of kidney functions ... of the urinary system consists of the kidneys the ureters the ... bladder and urethra along with Associated nerves and blood ... vessels most of the lecture and most of the hardcore ... physiology that happens with the urinary system is going to ... be happening with the kidneys so you know we're going to ... spend the most time really focusing on what the kidneys ... doing that at the end of lecture will hit these other ... things are functions of the urinary system include ... regulating your blood volume and I'll basically regulating ... how much water is in your blood remember water is the ... main component of your blood and fire just you know by your ... kidneys being able to adjust how much water you retain or ... how much water you get rid of that's going to directly ... influence your blood volume which of course in turn is ... going to influence your blood pressure so your kidneys play ... a big role in determining your blood pressure because they ... determine your blood vial. We'll talk about the kidneys role in PH adjustment you ... know remember your blood pH has a very tightly ... controlled level between 7.35 and 7.45 your kidneys along ... with your respiratory system play a role in adjusting the pH of your body. Osmolarity that again just refers to the concentration of ... body fluids and you know by adjusting what you're getting ... rid of your kidneys and because your blood is in ... contact with all the other tissues in your body your ... kidneys play an important role in adjusting osmolarity ... throughout your body and then sings like glucose ionic ... compositions of these various ions it's important obviously ... the kidneys need to get rid of waste products things like ... urea which is a breakdown product of nitrogen containing ... substances that's a big waste product ammonia things like that. And then finally don't forget off from the endocrine chapter ... that the kidneys actually also release some hormones such ... as renin and a referral poem. All right so let's start by talking about the anatomy and ... histology the kidneys are the kidneys I have a bean shape to them. And they're located just above the waist between the ... peritoneum and the posterior wall of the abdomen and if ... you remember from the digestive system chapter. Are the kidneys are considered retroperitoneal ... okay so here's a pretty good picture looking at you know at ... this side of someone and you can see why there would be ... like the peritoneum right there you can see highlighted so ... clearly this is a retro peritoneal organ they're ... partially protected by the 11th and 12th pairs of ribs if you ... remember from A&P 1 those are considered you are ... floating ribs because they don't attach to your sternum. You should also know that because of the liver the liver ... you know is mostly on the right side of your body so it's ... going to push the right kidney down and make it slightly ... lower than the left. Alright here's a frontal section of the kidney so you can see ... or a coronal section whatever you want to call it there's two ... main areas to the kidney to be aware of the outer part is ... called the cortex. And then the center part. Is called the medulla and in terms of the physiology that I ... mentioned before again the three main physiological ... processes that are going on in the kidneys are filtration. Re-absorption and secretion OK the filtration part is going ... to happen some place out in the cortex. And then the other two parts the reabsorption and the ... secretion are going to happen some place in the in the medulla. Eventually the medulla is going to collect the urine and ... it's going to drip right off of these little tips here that I'll tell ... you about in a second and be collected in the urine will ... initially pool in this area. And then of course the ureters what you see here ... we'll take the urine away from the kidney and bring them to the bladder. Now if you look inside of the medulla are these triangular ... shaped things that you have here those are called pyramids. And they contain the kidney secreting apparatus and the ... various to bills will go through those in a moment running in ... between the pyramids are something called the renal ... columns there's going to be blood vessels inside there and ... fibrous material that big basically helps anchor the ... cortex to the medulla if you look the tissue or at least the ... color based on this picture here of the renal columns is ... very similar to color that you're seeing eye in the cortex. Now the renal papilla is basically the tip of each of ... these pyramids okay and. Another word papilla means like nipple and basically that's ... where your final version of the urine is going to drip out of it ... drips off of one of these renal papillae and then it's caught. Buy what's known as a minor calyx that you can see it there ... so the the tip of the pyramid is called the papilla the urine ... drips out of there it's called by a minor calyx. Two or more minor calyces will come together and then ... the name changes and you refer to it as as a major calyx. Eventually all of the major calyces will dump into the ... middle area that's known as the renal pelvis. And then like I said the ureter will that carry the urine away ... from the kidney the important one of the important points ... from this diagram but now is that once the urine drips out ... of the papilla and is caught by these minor calyces That's that's the final version of the urine you can't change ... the urine anymore from that point on it's all about just ... collecting the urine and eventually bring it to the ... bladder so that it can then get out of your body. Now you know the kidney is considered a solid organ and ... like many solid organs it has an area where the blood ... vessels and other important structures attached to the ... kidney and once again if you remember they typically refers ... to those areas as like a hilum so this area would be the hilum The kidney and you're going to have like your renal artery ... coming in there you can have the renal vein leaving from ... there going to be ureter coming out of there so that ... whole area would be called the hilum on the way the hilum ... works is it sort of expands into a cavity as it goes into the ... kidney and they refer that cavity as the the renal sinus. The nephron we're going to talk a lot about in the second ... the nephron is the functional unit of the kidney it's ... microscopic so it's it's tiny but it's really important to ... understand you know the processes of filtration ... reabsorption and secretion so I'll spend a lot of time going ... over the anatomy of the Nephron in a moment. Now let's talk about the blood flow of the kidney okay one of ... the things that that can make the kidney a nightmare to ... learn is the fact that it's very vascular all right and that's ... not a surprise because really you know the job of the kidney ... is to filter your blood so you would expect there to be a lot ... of blood vessels inside of the kidney and unfortunately for ... you you're going to have to memorize the names of all ... these little blood vessels okay and get into it I think the next ... slide gets into it a little bit more detail but the two major ... blood vessels that you have are the renal artery which of ... course is a branch off of your abdominal aorta. And then the renal vein which takes the the blood away from ... the kidney and dumps it into the inferior vena cava. The renal arteries are huge branches of the aorta and up ... to 1/3 of the cardiac output can pass through the renal ... arteries to be filtered by the kidneys so you know the ... kidneys are getting a spot of blood flow and that's ... important for them to be able to do their job. The nightmare slide it shows you in excruciating detail all of ... the little blood vessels that you're going to encounter as ... you go through the kidneys all right and this is this is ... something you should definitely memorize it's ... something that's going to be useful for the next lecture ... exam but it's also something you could be asked about on ... the next lab practical and I think if you look in your lab ... guide you'll see there's a list here that you know I'll listen ... your lab guide as well so so make sure you Commit This to Memory. But basically like I said fresh oxygenated blood is going to ... come into the kidneys via the renal arteries. Then there's about five or so branches of what are called ... segmental arteries on the signal arteries then eventually ... branch and is they won in through those we know ... columns that I mentioned before they referred to as ... interlobar arteries run through the renal columns are ... interlobar artery then they make a fairly sharp 90-degree ... turn and they go a long time at the base of the renal ... pyramids and when they make that turn their then referred to ... as arcuate arteries. Now it's it's the arteries are obviously getting smaller and ... smaller as you go along eventually I after the arcuate ... arteries there's another sharp turn and the arteries will travel ... out into the cortex and that part at that point they're ... known as cortical radiate arteries or sometimes an older ... term that you'll see is interlobular arteries you can ... use either name just be really careful though if you use the ... word interlocutor it's not the same word is interlobar so ... make sure you spell it correctly interlobular is like i n ... t e r l o b u l a r okay so make sure you spell it right. After the interlobular arteries eventually get into these ... afferent arterioles they're going to bring the blood into ... the nephron at this little clump of capillaries that are called ... that's called the glomerulus or sometimes they call it the ... glomerular capillaries and this is actually a really important ... spot because that's where the filtration. A step of the renal physiology is going to take place that's ... where you're going to make your initial or you're pretty ... preliminary urine or your filtrate whatever you want to call. That's where the filtering of the blood takes place. As you leave the glomerular capillaries you go into an ... efferent arteriole so this is kind of a unique set up some ... things they like to ask you if you know exam questions ... about this this is really the only situation in your body ... where you have an arteriole go into a capillary bed and ... then instead of having a venule immediately taken ... away you have another arteriole so it goes arteriole, capillary, and then arteriole again so ... that's kind of a unique situation. After the efferent arteriole you get into a series of what are ... called peritubular capillaries then you get into peritubular ... venules then into cortical radiate veins and then into ... arcuate veins then into into interlobar veins and then into ... the renal vein so you can memorize it going up to like ... about you know like this this point then it just kind of ... reverse isn't goes backwards from what you learn for the for ... the arteries but I can't just to make sure you spend some ... time looking at this committing it to memory. So let's talk about the nephron now the nephron is ... microscopic and it's super important to understand the ... physiology so here's the Nephron. And there's two parts to the nephron this area appear. Is known as the renal corpuscle and a the renal ... corpuscle is what's going to have that glomerulus or you ... could call it the glomerular capillaries inside of it and pay ... so that's the renal corpuscle all the other things that are ... traveling around here are known as the tubules and ... they're going to have some different names for the okay ... so again just to remind you after we know corpuscle is ... where you have the first step of the kidney physiology these ... filtration is going to take place here but then as you go ... through the tubules that's where the reabsorption and ... the filtration excuse me the reabsorption and the secretion ... steps are going to take place. Eventually. All of the urine will drip out through a papillary duct in this ... is what they're showing you down here this would be the ... tip of one of those renal pyramids this would be a papilla here. And from here you can see the year they tried to draw ... them as diagram you can see the urine dripping off your ... once the urine drips out from here it's not going to be able ... to be modified any further at this point that the purpose is ... just to collect it and eventually get it outside of your body. So as mentioned each and each nephron is going to ... receive a blood from one afferent arteriole. Which divides into this Tangled ball-shaped capillary ... called the glomerulus or you can call it the glomerular ... capillaries whatever you want to call it eventually the blood ... is going to leave using the efferent arteriole that I ... mentioned before. As I said glomerular capillaries are unique in that they are ... positioned between two arterioles rather than the ... usual set up where you have an arteriole then a capillary ... bed and then a venule. So let's delve a little bit more into the details in the nephron ... again there are two major parts to the nephron there's ... the renal corpuscle which we'll talk about now and then ... there's all of these tubules which we'll talk about in a ... second if you look at the renal corpuscle there's two parts to it. The glomerular capillaries that I've talked about several times ... now which you again you can refer to just as the glomerulus ... if you prefer and then surrounding this capillaries is ... something called the glomerular capsule or what. Old people like me refer to as Bowman's capsule alright ... Bowman's capsule is a double-walled epithelial cup ... that surrounds the glomerular capillaries. And if you looked at a Bowman's capsule they kind ... of use the same type of naming convention that they ... use for serous membranes so again Bowman's capsule has ... two layers. The layer that's directly ... attached to the capillaries themselves is known as the ... visceral layer. Then there's going to be a little space and then the layer ... that forms the outer wall is known as the parietal layer ... okay now the visceral layer is a modified simple squamous ... epithelium it's made of the special cells called podocytes ... the prefix pod is the same thing like in podiatrist and it ... means feet so this means feet cells are they have these ... funny little projections on them that that look I guess like little ... feet called pedicels okay and they're going to wrap around ... the layer of endothelial cells that make up the wall of the ... the capillary itself. Then you have the parietal layer as I mentioned that's ... also going to be a simple squamous epithelium so let ... me show you a picture of this close up. And so here's this whole thing would be the renal corpuscle. Are the capillaries are on the inside and then the layer ... that's a Bowman's capsule that's directly attached the ... capillaries would be the visceral layer of Bowman's ... capsule then and here you would have both space in this ... outer layer is going to be the parietal layer of Bowman's ... capsule all right if you looked at a super duper close up then. of this Of the capillaries here this is what it would look like okay in ... yellow you're seeing the end of filial cells of the capillary ... wall itself and if you remember going back to the blood vessel chapter. The the kidneys actually have a fenestrated capillary okay ... and you know that that's why you see all the little tiny holes inside. After that you know you're going to bolt a seat if you look ... on the outside here this is some of those weird-looking ... podocytes that I mentioned are the ones that are making ... up the visceral layer of Bowman's capsule you can ... see the pedestals that are extending from it now in ... between the pedicels are something called the filtration ... slits that you can see here. shown in red The basal lamina is the third layer which kind of represents ... the the fused basement membranes from the end of ... seal cells as well as from the podocytes that's what makes ... it the basal lamina okay now why this pictures importing ... they refer to this this whole structure here they refer to ... the wall of it I should say as the filtration membrane in this ... is important because this is the wall that fluid and other ... materials has to cross to get out of the capillaries and into ... Bowman's space and that process as I've said a couple ... of times now that's referred to as filtration and that's the first ... step in making urine okay. So you know you can see if you read over here. The fenestrations that are part of the endothelial cells they're ... going to prevent the filtration of blood cells but they're going ... to allow other components of the blood to pass through so ... large your things will be able to start to pass through okay ... but the basal lamina part is going to prevent the filtration ... of larger proteins and then the slit membrane for the filtration ... slit that runs between the pedicels is going to prevent ... the filtration a medium-sized of proteins okay in a little bit ... when we start going into the physiology I'll actually tell you ... you know what kind of substances can pass through ... the filtration membrane and what kind of substances I ... can't but you know any big cells they're not going to be ... able to get through in any any medium or large size proteins ... they're not going to be able to get through. Fluid filtered from the glomerular capillaries is going ... to end up in a Bowman space with time or what they ... sometimes called the capsular space and that's going to be ... your initial urine or your preliminary urine or your ... filtrate whatever you whatever you want to call it okay it's not ... going to be the final version of the urine because you still ... have to take into account those two other processes the ... reabsorption in the secretion are they all talk about later ... this slide shows you some of the forces that are at work ... that caused the filtration to happen it I don't really want to ... get into him just yet but if you just glance at the names on ... these names are very similar to what you learned about ... what we talked about bulk flow and capillary exchange ... I'm in the blood vessel chapter okay. Blood plasma is filtered through the glomerular ... capillaries into the glomerular capsule from Once once ... you're in Bowman space though the fluids not going to ... stay there for very long it's going to continue on and now ... it's going to start to go through the tubular part of the ... Nephron so let me talk about the two bills the very first to ... view you come to is something known as the ... proximal convoluted tubule. How do you then go into something called The Loop of henle. Even after the loop of henle you going to something called ... the distal convoluted tubule from there are you going to ... collecting duct then into a papillary duct and then the ... urine drips out through one of these papilla and is picked up ... by a minor calyx. The distal convoluted tubules of several nephrons are going ... to empty into a single collecting duct so if you look ... in the picture over here see these little branches that are ... attaching to the collecting duct those would represent the ... distal convoluted tubules of other nephrons that are ... connecting to it as I said eventually they converge into ... these larger papillary ducts which then drip the urine out ... through the pillow which is going to be picked up first by ... a minor KFC which then converge to four major Kayla ... cease which then all empty into the center of the kidney at ... the renal pelvis and then the ureters take the urine away ... and bring it to the bladder. The first part of the loop of henle are they like so they like ... to divide the loop of henle as you go from the proximal ... convoluted tubule you're going to go downward and you're ... going to be getting deeper and deeper into the medulla ... and that's known as the descending limb of the loop of henle. Once it goes down though it's going to be make a very sharp ... turn and come right back up again and then it's referred to ... as the a setting. And if you looked at the walls of these different limbs you'd ... find a at the descending limb is always very thin it's a ... simple squamous epithelium which means it's very ... permeable to fluid fluids able to come in and I can go out of ... the descending limb very easily where is if you look at ... the a sending them a portion of it could be thin just like the ... descending limb in which case it would be made up of a ... simple squamous epithelium although sometimes some of it ... can also be thick in which case the wall would be made ... up of a simple cuboidal or maybe a simple columnar ... okay I'm some nephrons are going to contain both thick ... and thin ascending lips. Now based on the length of the loop of henle and the ... presence of thin and thin segments in the a setting limb ... has can be sorted into two different categories all right ... you either or either have what's called a cortical ... nephron which is shown here or you have a juxtamedullary ... nephron okay with a cortical nephron. Notice the renal corpuscle is fairly you know it's it's it's it's ... certain way out in the cortex all right it's actually very close ... to What's called the capsule which surrounds the entire ... kidney okay that's where you would find the renal corpuscle ... and another thing to notice with a cortical nephron is that ... the loops of henle don't dive down very deep into the ... medulla this would be the medulla part down here so ... you can see the loop of henle doesn't go very deep into it ... where is juxtamedullary I think it helps to know what the the ... word juxtamedullary the word juxta means like near to or ... close to in the medullary means medulla they got this ... name because noticed that the renal corpuscle sits a lot ... closer to the medulla area then the renal corpuscle of a ... cortical nephron does okay it's farther away so you know in ... both cases the renal corpuscle is still going to be ... out in the cortex but. Adjust the medullary won the ... renal corpuscle sits closer to the medulla than it does in a ... cortical nephron. Another key thing to notice about the juxtamedullary ... nephron is look at the Loop of henle alright they have these ... really long Loops of henle that go down deep into the medulla. And those long Loops of henle are really important when we ... start when we start talking about the kidneys ability to ... make either I dilute urine or a concentrated urine so we'll ... talk about that a little bit later on. Cortical nephrons are the most common they make up ... 80 to 85% of the million or so nephrons ... that are in the kidney their renal corpuscle is as I sat are ... going to be located in the outer portion of the cortex and ... they're going to have short Loops of henle okay that only ... go a small ways into the medulla. If you look at the a sending limbs of the loop of henle ... they're only made up of a sick part they don't have any thin ... portions to them. And then the the nephrons. Received their blood supply only from this group of blood ... vessels called the peritubular capillaries okay so after you if ... you remember the blood supply you're going to have ... an afferent arteriole going to the glomerulus then you're ... going to have an efferent arteriole come out and then ... after the efferent arteriole you'll encounter these ... peritubular capillaries. So here's another picture of a cortical nephron. You'll notice again the. Renal corpuscle is way out in the cortex it has a very short ... Loop of henle and then notice you know as the blood moves ... away from the glomerulus as part of the efferent arteriole ... you then go into something called the peritubular ... capillaries which is shown surrounding here okay so the ... peritubular capillaries are what are used to supply blood to ... the tubules basically. So the juxtaglom excuse me the juxtamedullary nephrons ... they only make up 15 to 20% okay they have a renal ... corpuscle that lies deep in the cortex and sits very close to ... the medulla thus named juxtamedullary and then they ... also have these really long Loops of henle that penetrate ... deeply into the medulla if you look at their a sending Lambs ... it's going to be a combination of Thin and Thick a segment. Now another thing you need to know about him to is ... because they have such long Loops of henle they have to ... have special blood supply to provide the blood to these ... long loose and they do in in addition to having the ... peritubular capillaries they also have long blood vessels ... called Vasa recta that are specially designed to provide ... the blood to the long Loops of head. Here's a picture then of a juxtamedullary nephron okay ... so notice the renal corpuscle sits you know relatively close ... to where the medulla is. I noticed the really long Loop of henle that goes deep into the medulla. And then notice on this picture these blood vessels that you ... see here that are following. The loop of henle those are called the Vasa recta all right ... you still have peritubular capillaries but the peritubular ... capillaries are mostly supplying blood to the ... proximal convoluted tubule and the distal convoluted ... tubule whereas if you want to get blood to the loop of henle ... you have to use the Vasa recta okay and for the life of ... me I have no idea why they didn't label these Vasa recta ... here but if you just want to write me to put an arrow to ... these blood vessels and just call it the Vasa recta that's ... probably a pretty good idea. Another thing you should know about the nephron is ... there's an area known as the juxtaglomerular apparatus so ... if you look at a nephron the final part of the ace ending ... lamb of the loop of henle actually makes contact with ... the afferent arteriole. And if you look at that last part of the a sending limit the ... loop of henle the cells that are in the wall there are very ... clumped closely together and they refer to that as the ... macula densa okay which means like dense spot and ... when you look under a microscope if you're lucky if ... you look in this area you can often see the macula densa ... you can at least see how the cells are kind of bunch ... together very tight. I'm alongside the macula densa if you look in the wall of ... the afferent arteriole at South you're going to find some ... modified smooth muscle cells that are called juxtaglomerular cells. So if you look at these two things together the ... combination of the macula densa which is in the wall of ... the ascending limb of the loop of henle and the ... juxtaglomerular cells which are in the wall of the afferent ... arteriole together they refer to that whole thing as the ... juxtaglomerular apparatus so let me try to show you a ... picture of that so it makes maybe a little bit more sense okay. So on this diagram here they're showing you a super ... duper close up of the renal corpuscle over here and then ... right over here they're showing you like the last part ... of the a sending limb of the loop of henle okay by the way ... the other name for the loop of henle that they sometimes ... use they just call it the nephron loop so. Or if I can go back actually let me go back just for a moment ... to one of these other pictures. So. If you look at this picture I hear what they're talking ... about would be like in there if there's a basically focusing on ... like this little area right in here that's where you're looking at ... when you're trying to look for the juxtaglomerular apparatus ... okay so let me go back to the close up then. Alright so here's here's the clothes up and if you look like ... I said in the wall of the a sending them of the nephron ... loop you should find some closely packed together cells ... that they call The Jug this method called the macula densa. And then if you look in the wall of the afferent arteriole ... you should find what are called juxtaglomerular cells ... okay and so collectively this whole thing is referred to as ... the juxtaglomerular apparatus and it's really important for ... helping to regulate your blood pressure okay and I'll talk ... about sort of how that works if you remember before way ... back in the endocrine chapter when we are talking about the ... RAS the renin-angiotensin-aldosterone system. It's actually the juxtaglomerular cells that are ... in charge of releasing the the renin. All right so that's kind of the end of the anatomy part of the ... kidneys that I want to talk about now I'm going to spend ... a significant amount of time talking about the physiology. Of the kidneys what's going on and is upset a couple of ... times there's three basic processes that are going to ... happen the first step is always glomerular filtration that's ... happening at the renal corpuscle part and then you ... have these two other steps that can take place that are ... going to happen along the tubules someplace you have ... reabsorption and secretion okay so with filtration you ... make your initial urine or your preliminary urine that's called ... the glomerular filtrate. Re-absorption is a step that allows your body to basically ... look at the preliminary urine and decide whether there's ... maybe some substances that it doesn't want to get rid of ... that it would actually like to hold onto so reabsorption is a ... way to look at the preliminary hearing and say you know ... what I really don't want to get rid of that let me let me hold ... on to it let me reabsorb it and bring it back into the blood so ... that I don't get rid of it. Versus secretion is a way of looking at the at the urine and ... saying you know what there are some materials that ... maybe you were too big to make it in make it through the ... filtration membrane but there are still things that I actually ... want to get rid of so during secretion it's a way of putting ... materials into the two bills so that you can get rid of a ... materials that maybe like I said we're just too large to ... make it through the filtration membrane and get into the ... urine that way. So here's a diagram that shows the the three-step sort ... of taking place there I'm after you've done all three of these ... steps that's what we'll give you your final version of the ... urine that you'll actually get rid of. All right so filtration is always the first step and as I started ... to show you on one of those earlier slides it's all about ... pressure that that controls filtration and those pressures ... are really the exact same pressures that you learned ... about in the blood vessel chapter when we were talking ... about you know bulk flow. It's happening during capillary exchange are you got to ... remember the glomerulus it's just a capillary bed okay so no ... surprise all of those forces that you learned about before ... with capillary exchange like the blood hydrostatic pressure ... in the blood osmotic pressure all that stuff is going to still ... apply I'm here okay there are some slight modifications but ... it's still basically are the same type of math problem that you ... had to do in order to figure out which way the fluid was going to move. Now I'm in the average adult the body's entire extracellular ... fluid volume will be filtered about 12 times per day. And in an average like you know man that's like 70 kg in body weight. That's going to be a you know the extracellular fluid volume ... is going to be about 14 years. Not all substances can pass through the filtration ... membrane that's really important to remember I ... showed you a close-up of that filtration membrane here's a ... little table website that shows you some of these ... substances and I'm going to keep coming back to this table ... as I go through the other physiological processes but ... for now just kind of focus on these two columns here that ... are in green where it says the amount in plasma and then ... the amount infiltrate. And again you're looking basically on a on a 24 hour basis okay. So if you look here you can see that you know in your ... plasma you've got about 3 L of water and if you consider ... the fact your blood is going to keep circulating again and ... again and again and through your kidneys throughout the ... day and if you counted the amount of water that showed ... up in Bowman's space. You know throughout the entire day. About 180 L of water would be showing up as the kit as it ... continues to recirculate okay what's the point the point is is ... that water has no problem getting through the filtration ... membrane so water is easily fill. If you look at glucose there's about three grams of glucose ... in your Plasma in on a daily basis as the blood recirculates ... through your kidneys I'm about a hundred and sixty-two ... grams is going to show up in your filtrate okay again the ... point here is that glucose is easily filtered it has no ... problem getting through the filtration membrane urea ... which is a waste product of. When you when you break down like amino acids things ... that contain nitrogen that's has no problem being filtered ... or creatinine which comes from you know the breakdown ... of like creatine phosphate from inside your muscles. That's also going to be easily filter okay obviously I skipped ... over one of them that's cuz protein if you look here you ... got about 200 grams of protein in your plasma. But on a daily basis only about 2 grams of protein is ... showing up in the filtrate okay so the take-home message ... has protein in it usually cannot get through the filtration ... membrane okay the only proteins that are going to be ... able to get through our once I give you really really small ... okay you know but anything that's medium large size ... there's no way that it's going to get into the filter. Now the important thing to remember from this table ... though is just because of material lines up in the filtrate ... though doesn't mean it's necessarily going to wind up ... in your final urine okay and I'll talk about these other two ... columns in a mole. So what makes filtration happen it's all about pressure. You know the four pressures that you had when you talked ... about bulk flow in the capillaries and if you recall ... from the blood vessel chapter you had blood hydrostatic pressure. And then interstitial fluid osmotic pressure being the ... key factors that were going to force fluid out of blood vessels ... and into the tissues and then you had the blood colloid ... osmotic pressure and the interstitial fluid hydrostatic ... pressure as being the forces that are going to try to move ... fluid back into the blood. You basically have those same pressures here to go ... with slightly different name so essentially your your your ... your blood hydrostatic pressure they refer to as the ... glomerular blood hydrostatic pressure so that's an outward ... Force okay that's going to be promoting filtration that's ... going to be trying to move fluid out of the blood vessels ... and into Bowman's space. You also have capsular hydrostatic pressure okay that ... would be due to the fluids building up in Bowman's ... space okay that pressure never really gets all that high ... because you got to remember that Bowman space is ... connected up with the proximal convoluted tubules ... so fluid is constantly being carried away from Bowman ... space so that value doesn't get very high. Another factor is the blood colloid osmotic pressure and ... you know that's a fairly high pressure that's going to be ... trying to pull the fluid back into the blood vessel so that's ... going to be opposing filtration. And then the fourth possible factor which would be ... analogous to like your interstitial fluid osmotic ... pressure would be your capsular osmotic pressure okay. You know that. In a healthy person is going to be very very tiny and that's ... because in order to have a high osmotic pressure you ... really need protein and in a normal healthy person very ... little protein is going to be getting into Bowman space so ... you can essentially ignore this fourth possible factor and just ... look at these three factors okay and it's going to be a ... math problem just like you did before I'm so what you're ... going to do is you're going to take the first guy. And then you're going to subtract from it. The sum of the other two guys okay and let me go on ... then to the next slide which shows you that. So you're going to take the glomerular blood hydrostatic ... pressure which is an outward Force which is promoting ... filtration and you're going to subtract from it the two other ... forces that are trying to pull the fluid back into the capillary. And if you do that you'll see this is the value you get so you take 55. And you subtract from 8:15 and then subtract from at 30 ... and you should get a value of 10 mL of mercury okay and ... the fact that it's a positive value means that this Force. Is beating out the other two forces another words you're ... making urine which is a good thing you always want this to ... be a positive value okay if this ever becomes you know a ... negative value that's an indication that your kidneys ... are not working properly that you've stopped making urine ... so that would actually be a very bad thing. A value that you sometimes see calculated in clinical ... settings especially like in a patient that might be in the ... Intensive Care Unit would be something called the ... glomerular filtration rate. This is the amount of filtrate that's formed in all the renal ... corpuscles of both kidneys every minute so kind of ... represents the total filtration that's taking place every min. An average man it's about 125 per minute in an average ... woman it's about 105 ml per minute or if you want to look ... on a daily basis it's about a hundred and eighty in a man ... in about 151.2 l in a woman so that's how much. Filtrate or how much preliminary urine you're ... making on a daily basis. Obviously that's a huge amount and like I said before ... that does not represent your final urine okay if you if you ... peed out that much urine each day you would clearly become ... dehydrated very quickly so we'll talk about that later but ... that's at least how much of the initial urine you're making ... on a daily basis to stay relatively constant. For proper homeostasis of your body fluids okay if the ... glomerular filtration rate gets too high. Then the urine Mike flow too quickly through all of the ... tubules and you won't be able to reabsorb materials properly ... and so you might actually end up getting rid of some ... important materials in your urine that you didn't really ... want to get rid of so you don't want the glue made a filtration ... rate to be too high or else you might lose some important ... things in your urine on the other hand. If it's too low you might have too much reabsorption taking ... place and then you might be retaining waste products that ... you might have I actually wanted to get rid of. There are three mechanisms that your body will use to ... control the glomerular filtration rate to keep it more or less ... stable okay there's something called Reno autoregulation ... that's where the kidneys themselves maintain a ... constant glomerular filtration rate. I understand two mechanisms that are involved in that that ... I'll discuss in a moment but it's it's the ability of the kidneys to ... keep a fairly stable glomerular filtration rate. Even though your systemic blood pressure can change ... throughout the day. Neural regulation refers primarily to sympathetic ... neurons regulating blood flow and regulating glomerular ... filtration rate. Women hormonal regulation refers to things like ... Angiotensin II or atrial natriuretic peptide on your ... kidneys to regulate the glomerular filtration. So let's talk about the renal autoregulation again there are ... two mechanisms that are going to be used by the ... kidneys to the themselves to make sure that the glomerular ... filtration rate stays about the same even though you'll have ... daily fluctuations in your stomach blood pressure okay ... one of them is called the myogenic mechanism ... basically the walls of the are afferent arteriole are sensitive ... to changes in blood pressure. And the smooth muscle in the wall will contract if the blood ... pressure increases or relax if it decreases okay so if your ... systemic blood pressure were to increase okay. That would ultimately lead to a very high glomerular blood ... hydrostatic pressure okay and that would in turn would lead ... to a very high good made a filtration. But by Contracting. The smooth muscle in the wall of the afferent arteriole would ... you know when the when your systemic blood pressure is ... high by Contracting that will reduce the amount of blood ... flow that gets into the glomerulus and thereby bring ... down your glomerular blood hydrostatic pressure so you ... so that you don't end up having a super high ... glomerular filtration. On the other hand if you're systemic blood pressure was ... running very low on you would want the smooth muscle in the ... wall of the afferent arteriole to relax in other words to dilate ... to try to let is much blood flowing into the glomerulus as ... possible to try to keep up a very high going to be in the ... blood hydrostatic pressure so that you're limited or filtration ... rate doesn't fall too much just because you systemic blood ... pressure had fallen. The other mechanism is called the tubular is called ... tubuloglomerular feedback okay and this is going to ... involve that juxtaglomerular apparatus that I mentioned ... before okay remember the macula densa that's in the ... wall of the last part of the ascending limb of the loop of ... henle that area is actually able to monitor how much sodium ... and chloride and water is coming in or it is present in ... the urine of the ascending limb of the loop of henle. If those items sodium chloride and water are high okay that's ... a suggestion that urine is being made to quickly that you ... have a kilometer filtration rate that's too high and under ... those circumstances the macula densa will send a ... signal to the afferent arteriole and cause the smooth muscle ... cells in the wall of the afferent arteriole to contract when that ... happens that's going to reduce the blood flow that ... gets into the glomerulus which in turn will reduce the ... glomerular blood hydrostatic pressure which in turn will ... reduce your glomerular filtration rate. On the other hand if you have low amounts of sodium low ... amounts of chloride low amounts of water that's a ... suggestion that you're not making the urine quick ... enough another words that's a suggestion that the glomerular ... filtration rate is too low under those circumstances. The macula densa will send signals that are basically ... caused the smooth muscle in the wall of the afferent ... arteriole to relax another word the afferent arteriole will dilate. That will allow as much blood to flow into the glomerulus as ... possible which will lead to a high. Glomerular blood hydrostatic pressure which will in turn me ... to a higher glomerular filtration. An effort to try to increase how quickly you're making your. Neural regulation of the glomerular filtration rate really ... refers to what sympathetic neurons are doing if you ... remember back in amp1 it's mostly your sympathetic ... system that connects up with blood vessels and not your ... parasympathetic system okay there are some exceptions but ... primarily it's sympathetic neurons that connect with ... blood vessels and you know the afferent arteriole is richly ... supplied with sympathetic neurons that can cause ... vasoconstriction okay and of course when you constrict the ... afferent arteriole. That's going to reduce the amount of blood that flows ... into the glomerulus and when the amount of blood in the ... glomerulus is reduced that's going to reduce the glomerular ... blood hydrostatic pressure which in turn is going to ... reduce the glomerular filtration rate okay now at rest those ... sympathetic neurons are not very active. And the glomerular filtration rate is mostly going to be ... controlled by the renal autoregulation that I ... mentioned on the previous lot. But during an activity such as exercise okay or for example ... if you had lost a lot of blood from like a trauma situation ... and you had Hemorrhage are those neurons are going to ... become very active. And you can see a market drop in renal blood flow and ... the glomerular filtration rate under those circumstances ... okay so if you're exercising or if you've had a lot of ... hemorrhage okay there's a there can be a big drop-off in ... urine production because what will happen is the ... sympathetic neurons will send signals to the afferent arteriole ... to the smooth muscle that are there they will constrict. That's going to decrease the amount of blood flow that gets ... into the glomerulus which in turn decreases the glomerular ... blood hydrostatic pressure which in turn decreases the ... glomerular filtration rate and that's going to significantly ... reduce your urine output which you know in an exercise ... situation or especially in a hemorrhage situation you ... usually don't want to decrease your blood volume okay ... another would you don't want to make a lot of urine during ... these situations you want to hold on to as much blood ... volume as possible in order to be able to maintain a good ... blood pressure to keep the blood flowing throughout your body. And also what that will do is by sending less blood flow ... you know into the kidneys it's going to be able to send more ... blood flow to other tissues that really need it so you know ... during exercise you know you're going to want to send ... more blood flow to you like your skeletal muscles for exam. Or you going to want to send more blood flow to like the ... coronary vessels to supply your heart with a blood supply ... that it needs you don't need to send as much blood flow you ... would want to send as much blood flow to the kidneys. And then finally there is a hormonal regulation the ... glomerular filtration rate and there's two important ... hormones that play a role in Angiotensin II if you ... remember Angiotensin II is a big vasoconstrictor throughout ... the body okay and it actually can cause a constriction of ... both the afferent and efferent arterioles and the result of ... that especially of constricting the afferent arteriole is to ... reduce the GFR okay anytime you constrict. The afferent arteriole you're going to be reducing the ... amount of blood flow that can get into the glomerulus and ... when that happens you're also going to be reducing the ... glomerular blood hydrostatic pressure which in turn will ... reduce the glomerular filtration rate. So you know Angiotensin II is usually released under ... circumstances when your blood pressure throughout ... your body is low and when you want to raise your blood ... pressure and the last thing you want to do when your ... blood pressure is low is to make a lot of urine okay you ... don't want to potentially you lose any of the fluid of your ... blood in your urine so it makes sense that Angiotensin ... II would reduce the glomerular filtration rate so that you make ... less urine in other words you're going to keep more of ... the fluid in your blood and not not get rid of it in your urine. On the other hand atrial natriuretic peptide if you ... remember this is a great hormone that you want to ... release when your blood pressure is too high another ... words when you want to bring down your blood pressure ... okay so how does it work on a glitch made a filtration rate will ... win this is this is released okay again this is going to be ... released basically when the walls of your Atria get ... stretched from having a blood pressure that's too high by the ... way it actually works is when it gets to the kidneys. In the wall of the glomerulus I didn't mention this before but ... in the wall of the glomerulus there are actually some ... smooth muscle cells they're okay and when a MP is ... released it causes the smooth muscle smooth muscle cells in ... the wall of the glomerulus to relax and what that does. Is it basically increases the surface area of the glomerulus. That's available to do filtration in the more surface area that you have. The easier it is to do filtration and the more filtration is going ... to take place okay so another words you're going to ... increase the glomerular filtration rate when a chill ... natural attic peptides around you end up making more urine ... in the more you're in that you make the more the fluid inside ... of your blood is going to drop and that's going to bring down ... your blood volume which in turn will bring down your blood pressure. Okay so that was filtration again filtration is always going ... to be the first step it gives you your initial urine or your filtrate ... but there are two other important things that are that ... are going to happen that are going to determine what your ... final urine are going to be like okay re-absorption as I ... mentioned is a way for your body to basically look at the at ... the preliminary urine and say you know what there's some ... materials in that initial urine that I don't really want to get ... rid of another words I'd like to hold on to them I'd like to ... bring them back into my body that's what reabsorption is ... okay so what kind of things are getting reabsorbed well ... water is going to get reabsorbed glucose is going ... to get reabsorbed electrolytes vitamins amino acids and then ... any small proteins that might have gotten into the filtrate okay. The vast majority of material that gets into the filtrate is ... gonna get reabsorbed 99% of the filtrate will get ... reabsorbed okay and most of that reabsorption two-thirds of ... it is going to happen in the proximal convoluted tubule ... and if you look at the proximal convoluted tubule okay. There's actually What's called the brush border of the ... proximal convoluted tube. And this brush border basically represents little ... microvilli so the cells that are in the proximal convoluted ... tubule they have tons of little microvilli on them. Which is there to increase the surface area so that they can ... more effectively do the reabsorption okay so that's ... important to keep in mind 2/3 of the reabsorption happens in ... the proximal convoluted tubule and actually when you look ... under the microscope. You know you're in you're trying to tell the difference ... between say a proximal convoluted tubule and a distal ... convoluted tubule you want to look for sort of a haziness ... inside of the proximal convoluted tubules all right ... they're not going to be you're not going to have a nice clear ... Lumen because of this brush border you know when you ... when you create the microscope slide when you look at. Alright so here's the same table as before but now I just ... highlighted a different column hear what I wanted what I'm ... showing you hear is how much of the stuff that got into the filtrate. You know gets reabsorbed. And you can see that like on a daily basis if you kept ... counting the water again and again and again there's $180 ... but almost all of that. Is getting reabsorbed so that in your final urine you know ... your your typical urine output per day is only about 1 to 2 L ... okay so tremendous amounts of reabsorption of water are ... taking place in that you know obviously that's a very good ... thing or you would become severely dehydrated. Likewise with proteins remember with proteins first ... off in proteins it's very hard to even get through the filtration step. But even if you get through the filtration step almost all of ... those proteins are getting reabsorbed so then your final urine. You have you know a very minut amount of protein in ... your final year. I'm glucose same type of thing glucose is freely filtered. All of its getting reabsorbed so in a normal individual you ... know you shouldn't have any glucose in the final year. Urea is kind of interesting urea gets freely filtered and ... then about half of it ends up getting reabsorbed so yeah ... you know having like 30 grams does it show up in the urine. um with uh creatinine uh creatinine is freely filtered okay. But then none of it ends up getting real reabsorb okay so ... sometimes when they want to evaluate how well the filtration ... process is happening they'll look at creatinine levels of the ... blood because it's a way of directly looking at the filtration ... process without confounding the results with what could be ... happening with reabsorption okay so it's this is a very ... common actually these are both very common blood tests ... the blood urea nitrogen and the creatinine levels are test ... that they'll do to evaluate kidney function and you can ... see again with the creatinine it's a way of just looking at the ... filtration stop without having to worry about reabsorption ... because none of the creatinine ends up getting reabsorb. Now when you do reabsorption there's two sort ... of methods that can happen the first of all what I want you ... to notice here this is a super duper close up. Of the proximal convoluted tubule like I said here you can ... actually see the cells this would be the brush border ... these a little microvilli that are on the surface and again by ... having microvilli it increases the surface area that's ... available for a reabsorption okay so I'm over here in the ... middle of course this would be the inside of the two of y'all. And you can see there's two general methods by which ... reabsorption happens paracellular reabsorption is ... when materials basically squeeze between the tubules ... sells okay it's a passive process. And it's so it's the material the reabsorption is happening ... between the cells versus transcellular resorption means ... that the reabsorb material is going directly through the cell ... membrane are the individual cells. Re-absorption of these materials you know in terms of ... the process it could either be active or passive this goes way back to. You know what earlier chapter in ep-1 remember active ... transport processes mean that energy is required ... passive processes mean that no energy is required. And then you know if you look at active transport there is ... something called primary active transport that's where ... you use ATP directly as the energy source and probably ... the most famous example of primary active transport would ... be like your sodium potassium pump. So that's a method of reabsorption at rest about 6% of your total body ATP use is used to power you know ... these these pumps secondary active transport gets its ... energy from the from the from the movement of one ... substance down its natural concentration gradient. You know the energy of motion the kinetic energy is ... then used to power the movement of a different ... substance against its concentration gradient. And I you know if you have the two substances moving ... across the membrane in the same direction those are ... referred to as symporters if the two substances are ... moving in opposite directions those are referred to as anti course. So again this is still requiring energy it's just using the ... kinetic energy of motion of one substance in order to ... power a different substance against its concentration gradient. And then passive transport processes again those ... referred to not needing energy to make the substance move ... across a membrane by diffusion. Again it's just a natural property for a substance to ... move from the side of a membrane where it's in high ... concentration to the side where it's in low concentration ... and then ozmosis specifically refers to the movement of ... water the diffusion of water through a selectively ... permeable membrane. Here's a picture of showing you the two types of ... secondary active transport again anytime with secondary ... active transport you're going to have one substance that's ... following its natural diffusion gradient. That's going to be providing the kinetic energy that's ... needed to move a different substance against its ... concentration right so in this example I will actually in all in ... all the three examples that you see here the natural ... substance that's moving is sodium. Okay. And then your coupling that motion with something ... different so in this example you have sodium moving in naturally. And the energy of motion of the sodium is using to move ... glucose in at the same time okay because the two ... substances are moving in the same direction across the cell ... membrane this is an example of a symporter. Verses in this example. You're actually using sodium. Moving in one direction to move hydrogen in the ... opposite direction so this would be an example of an antiporter. Likewise. In this is this example I'm you're using a sodium moving ... in One Direction and then hydrogen moving in the other ... direction so that would be another example of a Nancy Porter in. Because they're moving in the opposite direction is opposed ... to moving in the same direction. Actually sorry these these two pictures are showing you the same. They're showing you the same antiporter this is ... showing you basically the first step. And then this is showing you the second step and how this ... antiporter can actually be used in order to get ... bicarbonate to be reabsorbed through the sort of chemical ... reaction here but anyway the point is an antiporter is when ... you have two substances are moving in opposite directions ... across the cell membrane. Passive transport just means that no energy is required to ... make the movement happen so you know appear you can ... see like chloride potassium calcium magnesium urea they ... could do passive transport either you know paracellular ... route or they can do a transcellular route on same ... thing down here with water again that the fancy name for ... when you do diffusion of water is just osmosis and it ... could be either a paracellular or it could be transcellular Now I'm a little bit more though it's to say about water ... so let me talk a little bit more well I shall move it the water ... part of come up again a little bit. Actually the next slide gets into water again but before I ... go into that let me just talk about something that's known ... as the transport maximum and the renal threshold okay you ... know in order for all of these substances to be reabsorbed ... there actually have to be little ion channels or other things ... that are present okay and every every transporter has ... what's called a transport maximum okay that's the ... maximum amount of a substance that can be ... reabsorbed Express in milligrams per minute okay ... you don't have an unlimited supply of Transporters there's ... a finite number of Transporters and it is possible. To Simply have too much of a mature of a particular material ... in your urine that you overwhelm the Transporters in ... other words you don't have enough Transporters in order ... to reabsorb all of the material that you would like okay. I'm in that considered the topic of What's called the ... renal threshold the renal threshold refers to the ... concentration of a substance in the blood. For the filtrate that once you go above that amount. You're going to be overwhelming the transport ... maximum for that particular chance. So what did okay what do I actually mean by that so free ... sample let's take glucose as an example okay. You know in a healthy individual you know assuming ... you don't have a problem like diabetes you're going to have ... normal blood glucose levels and when the blood gets filtered. You're going to have you know you're going to have ... some some glucose showing up in the filtrate but you're ... going to have plenty of Transport is available to ... reabsorb that glucose so that in your final your end you ... won't see any glucose right. Let's suppose you had a problem like diabetes okay ... and you have really high blood glucose levels you know ... suppose you had like a blood glucose level of 200 mg per ... deciliter okay when that blood goes into the kidneys and it ... gets filtered you're going to have super high levels of ... glucose in the filtrate. In fact you probably have levels that are so high that ... you just won't have enough glucose Transporters to do all ... of the reabsorption that you would like to so what's going ... to happen well the only result is you're going to end up ... having some glucose show up in your final urine okay you ... just simply can't reabsorb all of the glucose you've ... overwhelmed the Transporters there's just not ... enough of the Transporters to reabsorb all of the glucose that you need. Okay so let me go back to the water re-absorption that I ... mentioned before so why reabsorption can be classified ... into two groups based on whether you your body can ... control it or not okay there's something known as ... obligatory water re-absorption which your body really can't ... control in other words obligatory means that the ... water re-absorption has to happen Okay water basically ... has to follow the solutes that are being reabsorbed in order ... to maintain the osmotic gradient. Obligatory reabsorption is usually going to happen ... earlier on in the tubules so obligatory reabsorption of ... water is what you typically see. You know mostly in like the proximal convoluted tubule ... okay and indy you know Loop of henle alright this is water ... re-absorption that just sort of has to happen you can't really control. Yes you can further along in the tubules as you get to like ... the distal convoluted tubule and as you get to the ... collecting ducts you then have more control over the water ... re-absorption and that's known as facultative reabsorption. You know what do I mean by control what I mean is you ... can influence how much water gets reabsorbed through the ... effects of hormones such as antidiuretic hormone and aldosterone. Those hormones can make the tubular cells more ... permeable to water so that you can get more water reabsorbed. When you don't have those hormones around the. Tubular cells become less permeable and the water ... basically is trapped inside of the tubules and you won't get ... as much reabsorption taking place okay so again just to. Just to summarize obligatory reabsorption your body can't ... control that that's water re-absorption that has to ... happen faculty reabsorption your body can control it ... through the effects of different hormones. Alright finally the third and final process that's going on in ... the kidneys is tubular secretion and this is a way as ... I said before your kidneys basically looking at the at the ... urine and saying you know what there's some material ... that's in the blood. That I don't want but maybe that material that was in the ... blood was just too big to make it through the filtration step ... but I still want to get rid of its secretion is a way of getting ... materials into the urine That Couldn't necessarily pass ... through during the filtration step okay secretion is always ... going to occur by active transport. A secretion is also the way that the kidneys can control the pH okay. You know so for example hydrogen in ammonium ions ... this is this is what ammonium looks like those are ways of ... getting rid of excess hydrogen ions when there's too much ... acidity in your blood okay so if the pH of your blood is getting ... too loud another words if your blood is becoming a city. Your kidneys can actually secrete extra hydrogen ions ... into the urine in other words get the hydrogen out of the ... blood put it in the urine and that'll help to raise the pH of your blood. You know another thing that you can do is you know when ... your blood is becoming too acidic is to conserve ... bicarbonate another words don't get rid of as much ... bicarbonate in your urine can serve the bicarbonate and ... that'll help raise the ph okay we'll talk more about this a ... little bit later on we'll also talk about it in. The next chapter chapter 27 which is devoted to acid-base ... balance in the body. Another thing sorry before I leave another thing I should mention to is. You know hydrogen potassium those items can ... also be secreted by the two bills and then some drugs you ... know the way that your body metabolizes certain ... medications I is through secretion some of your ... antibiotics for example in order to get them out of your ... system your body has to do tubular secretion right the ... drugs are just too large in size to be able to be filtered so you ... have to do secretion to get them out of the body. Maintaining the pH of the body really falls on two organ ... systems your lungs and your kidneys okay your lungs can ... adjust the body's pH by controlling how much CO2 is ... building up in the blood okay I'm the more CO2 that builds ... up in the blood the more acidic your blood will become. And so if you hyperventilate and you're going to be ... releasing more CO2 you're going to be getting the CO2 ... out of your blood and that's going to help to read to raise ... the pH of your blood on the other hand if you breathe ... more slowly if you hyperventilate that's going to ... retain more CO2 in your blood and that's going to be two ... more acidity of your blood and that's going to reduce the pH ... of your blood okay on the thing you should know about ... the lungs is that they work fairly quickly alright they work ... within minutes cause changes in the pH. Are the kidneys can also adjust the pH but like I said ... eliminating hydrogen or eliminating ammonium ions ... and by conserving bicarbonate about that ... process takes more step that occurs more slowly that takes ... hours to days in order for that to happen Okay so again will ... it will mention this more in the next chapter but I just wanted ... to put it out here your GI tract which is known as the ... alimentary canal or you can just call it that's an older term ... that means GI tract as well as your skin they can also adjust ... like hydrogen and in bicarbonate levels so they can ... play at a slight wall in a crawl and adjusting the pH of your body. Hormones can also play a role in adjusting the reabsorption ... in the secretion steps so you know so hormone Taino I had ... mentioned before how. You know you can take a hormone like Angiotensin II or ... atrial natriuretic peptide and how they can influence the ... filtration step how they can influence the glomerular ... filtration rate what hormones can also influence the ... reabsorption and the secretion steps and there's five ... hormones that can influence the extent that sodium ... chloride calcium and water re-absorption as well as ... potassium secretion take place in the tubules and so ... you know all of this hormones they're super important for ... effecting renal blood flow and blood pressure but also ... influencing systemic blood flow in systemic blood ... pressure so those five hormones are Angiotensin II ... antidiuretic hormone aldosterone HUD director attic ... peptide and parathyroid. You know I had mentioned Angiotensin II NHO naturally ... peptide before as affecting glomerular filtration but they ... can also have an impact on reabsorption and secretion. So yeah I did mention atrial natriuretic peptide in the ... glomerular filtration rate in Oho natural Reddit peptide ... can also promote the secretion of more sodium into ... the urine and when you have more sodium in the urine ... water will follow during us due to osmosis and the more ... sodium and water to get rid of in the urine. The more your blood volume is going to decrease and then ... the more of your blood pressure's going to go down ... okay it like I said before hu you know remember that ... remember the the meaning of the word a trail means it ... comes from the Atria natural Reddick is a word that means ... peeing out sodium getting rid of more sodium in your urine ... when you put more sodium. Into the urine water's going to follow due to osmotic ... properties and that's going to that's going to increase your ... urine volume but you crease your blood volume which will ... decrease your blood pressure. Antidiuretic hormone becomes from the posterior pituitary as ... hopefully remember for the endocrine chapter I generally ... released when there is low blood flow in in that part of the ... brain or when there's evidence of high a blood ... concentrations another words when there's evidence that ... your blood is super concentrated in other words ... when there's evidence that your body is dehydrated okay ... I'm a DHS acts facultative water re-absorption. Basically putting little channels into the cell ... membranes of water called the principal cells in the wall of ... the District of lewdity Bill and the collecting duct okay the ... main cells that make up the walls of the two bills are ... something called principal cells and if you were to look in ... the cell membranes of those principal cells in the distal ... convoluted tubule and collecting duct. You may have little water channels that are called ... aquaporins okay now. When ADH is not around you tend not to have as many of ... these aquaporins which means that you won't be able ... to do the facultative water re-absorption in the distal ... convoluted tubule in the collecting duct. When ADH is around you will see more of these aquaporins ... in the cell membranes of the principal cells which will mean ... that these cells are make more able to do a ... reabsorption okay you don't we we had talked a long time ... ago about how day eh promotes water re-absorption ... in the kidneys we just didn't get into the nitty-gritty details ... of what it actually does and that's and that's what it does it ... actually puts water channels known as aquaporins into the ... cell membrane of these principal cells which will allow ... them to reabsorb. All right so we've talked about what atrial natriuretic peptide ... does to reabsorption we talked about what antidiuretic ... hormone does let's talk now about what like Angiotensin II ... and aldosterone do to like absorption and secretion okay ... and to do that we have to sort of talked about that whole ... crazy raas system which is shown here again in all its ... Glory you know so when blood volume and blood ... pressure decrease or when the sympathetic nervous ... system is stimulated the walls of the afferent arteriole are ... stretched less and again in the walls of the afferent ... arteriole are where you have those juxtaglomerular cells ... and that's going to trigger the juxtaglomerular cells. To actually release renin as you see here okay the rent in ... his then going to seek out angiotensinogen which is ... made by the liver and it's going to convert the ... angiotensinogen to Angiotensin 1 Angiotensin 1 is ... going to go to the lungs where angiotensin-converting-enzyme ... is going to converted into Angiotensin II. And then the Angiotensin II he is going to do a basal ... constriction of arterioles throughout your body that's ... going to help to increase resistance throughout your ... body with your Lantern increase your blood pressure ... within the Angiotensin 2 is also going to go to the adrenal ... cortex and cause it to release aldosterone and when you ... have aldosterone released her own increases sodium and ... water re-absorption in the tubules of the kidney at the ... same time and also causes secretion of potassium and ... hydrogen on the reabsorption of the sodium along with the ... water is going to increase the blood volume which then in ... turn increases the blood pressure I'm just remember ... from this whole thing that you can bypass all of this ... nonsense and cause aldosterone to be released if ... you have high potassium levels in the extracellular fluid ... again high potassium levels in the blood is referred to as ... hyperkalemia. A life-threatening situation and ... if that happens that will directly cause a Dodge Ram ... release which is going to help you secrete more potassium ... which will help to bring down your blood potassium levels ... and help protect you from like cardiac arrest for exam. This like basically just reiterates you know the ... process of what's happening with the raas system and you ... know it's leaving out some of the steps but it just mention it ... one of the things go to mention about any attention to ... you no attention to is a great hormone to increase your ... blood pressure and it actually does it in three ways are two ... of the three ways I've mentioned several times you know. You know it causes vasoconstriction of your W-4 ... on Eastern and your Affair in arterioles and buy basil ... constricting especially the afferent arteriole that's going ... to decrease your glomerular filtration rate which in turn you ... know cause you to make less urine which again helps to ... increase your blood by. I've also mentioned the third step here as well I'm ... Angiotensin II causes aldosterone to be released. And that's you know of course going to help you reabsorb ... sodium and water but I didn't mention the second thing is ... you know Angiotensin II actually also directly causes ... reabsorption of water and electrolytes in the proximal ... convoluted tubule okay so all of these like I said all three of ... these things are great to do when your blood pressure is ... too low another which when you're having problems ... maintaining your blood pressure all three of these ... things are going to help to increase. Bob again just to go back to aldosterone aldosterone ... stimulates the principal cells in the collecting tubes ... specifically to cause them to reabsorb more sodium and ... chloride and at the same time to secrete more potassium. When you reabsorb more sodium and chloride that then ... is going to create an osmotic imbalance that then is going ... to attend a draw water along with it so as sodium and ... chloride gets reabsorbed Waters going to go along with ... it which is then going to increase your blood volume ... and increase your blood pressure. And then the last hormone that I mentioned that affects ... reabsorption on although I don't have a slide for it is a ... parathyroid hormone okay remember parathyroid hormone. Is a hormone that your body releases when your blood ... calcium levels are too low another words parathyroid ... hormone increases blood calcium levels and one of the ... ways that it does that is by going to the kidneys and ... promoting the reabsorption of calcium okay specifically. Parathyroid hormone works on the distal convoluted tubule ... to promote reabsorption of calcium. Okay let's go onto a slightly different topic and talked ... about how your kidneys or how your body control ... whether you make a really dilute urine or where do you ... make a concentrated urine okay. You know when you hear dilute or you hear ... concentrated urine I think you should think of a couple of ... things first of all the most important nephrons for doing ... this are going to be those juxtamedullary nephrons that ... have those really long Loops of henle that go deep into the ... medulla okay that's number one on the other thing that ... you want to think of when you hear this is think of antidiuretic ... hormone and I think of facultative water re-absorption ... okay I'm the key hormone that determines whether you make ... a dilute or a concentrated urine is antidiuretic hormone. You know when you are overly hydrated other words ... when you got too much water in your body. That will actually prevent your posterior pituitary from ... releasing antidiuretic hormone And when you don't release antidiuretic hormone you end ... up making a very dilute urine another words when and ... when ADH is not around you're going to pee alot and ... the urine that you make he's going to have a lot of water in ... it going to be a very clear looking you know very dilute urine. On the other hand when your body is very dehydrated that's ... going to stimulate the posterior pituitary to release ... ADH when ADH is around. It's going to put those little aquaporins into the cell ... membrane of the principal cells that are in the distal ... convoluted tubule and in the collecting duct and that's ... going to allow water to be reabsorbed in the DCT and in ... the collecting duct and the more water that gets ... reabsorbed the less urine that you're going to make in the ... urine that you do make is going to be very concentrated ... it's going to be like a dark yellow or even a brownish colored urine. So that those are the things you know that I want you to ... think about when you hear the term you know production of ... dilute or concentrated urine. Okay so let's talk about the first situation let's assume that ... you're overly hydrated another would you have too much ... water in your system. And what's going to happen to those circumstances well the ... posterior pituitary is not going to release ADH so you'll end ... up making a very dilute urine so let me walk you through it. This picture over here is from a cortical nephron and these ... numbers that you see inside and outside of the two bills ... how does represent how concentrated each fluid is in ... terms of milliosmoles per liter right this is just a general way of sort of. Grading the the concentration higher number indicates a ... fluid that's more concentrated lower number indicates a fluid ... that's less concentrated. And when you can see here is as you leave Bowman space ... going to proximal convoluted tubule you're going to have a ... concentration of about 300 Emilio's moles per liter right ... now as you go down the descending limb of the loop of ... henle more and more water is getting reabsorbed alright it's ... a you can see on this diagram it say it would be like a simple ... squamous epithelium so it's going to be very thin water ... gets reabsorbed very easily. You know as you reach the the band in the loop of henle ... you reach a maximum of about 900 million moles per liter. Now after you turn the corner though. The water is basically trapped inside of the loop of henle so ... as you go down. I should say as you go up the loop of henle as you're going ... into the a sending limb of the loop of henle. Other solutes are getting reabsorbed okay and it has ... the other side I use get reabsorbed noticed that the ... concentration is going to go down so water is trapped ... inside of the two of you but solutes are getting reabsorbed ... so you go from 900 down to 550 down to 350 as down to ... 150 down to 100 you know again water is trapped inside ... but solutes are getting reabsorbed this number is ... getting lower and lower another words the ... concentration is getting more and more dilute. Until finally. Your final version of the urine you've got a concentration of ... only 65 milliosmoles per liter per liter of a that's a very ... dilute urine another words that has a high water content to it ... but not that much solute So that's exactly you know this again is exactly what you ... would want to do if your to hydrate if you got too much water in your. Now let me show you a similar picture. First of all I should know it's a similar picture but in this ... diagram they're actually taking this from a juxta medullary ... nephron okay so the numbers that you see inside here are a ... little bit different than on the previous slide but basically ... the same pattern follows but I'll also to walk you through it ... okay to key difference between this slide. And the previous slide though is what's happening in the ... distal convoluted tubule and what's happening in the ... collecting ducts let me let me walk you through it again so ... as you leave bone in space going to proximal convoluted ... tubule you got a concentration in the tubules of about 300 ... Milio's moles per liter as more and more water gets ... reabsorbed that number's going to go up so you going to ... 380-587-8980 okay you reach a maximum in this example ... because it's a juxtamedullary of about 1200 Milio's moles per liter. As you start to turn the corner it's very similar to what you ... had before okay initially no water initially the water is ... trapped but solutes are being reabsorbed. And as the solutes are being reabsorbed again this value is ... going to go down okay so again so far this looks very ... similar to what you saw in the previous I slide as more sites ... without but now look what happens though when you get ... into the DCT in the DCT see these little black lines MK the ... black dotted lines and you see him also in the collecting ... ducts okay these indicate water re-absorption is taking ... place why is the water re-absorption taking place ... while because ADH is around in a t h has put these little ... aquaporin channels into the cell membranes of the ... principal cells of the DCT and the collecting tubules so that ... that's going to allow the water to get ribs or and so as water ... gets reabsorbed in the DCT and in the collecting duct look ... what's happening to the concentration right you are ... down at a hundred here. But instead of this number getting lower lower and lower ... like it did on the previous slide now all of a sudden it's ... starting to go up okay that's because water is getting ... reabsorbed and as more and more water gets reabsorbed ... the value goes from 200 to 300 to 3:20 to 400 all the way ... until you reach your final urine in this example with a ... concentration of 1200 Milio's moles per liter that's a very ... concentrated urine that urine would look like very dark ... yellow or maybe even brownish okay and this is ... exactly what you would want to do when you're dehydrated ... you would want to make a very concentrated urine and ... you wouldn't make much of it in an effort for your body to ... retain to hold on to as much water as possible. So again it's all about the ADH if you have a 82 round ... you're going to make a very concentrated urine if you don't ... have a DH around you're going to make a dilute urine ... okay now ath is what's in charge of putting aquaporins ... into the two bills cells so that the water can get reabsorbed ... but you may have asked yourself you know why does ... the water even want to be reabsorbed in the first place in ... the answer to that is because there's a really high ... concentration gradient that's trying to pull the water out of ... the tubules and into the interstitial space okay you ... know the truth of the matter is there's a very high amount of ... solute building up in the interstitial space of the renal medulla. That's trying to draw that water out and the deeper you ... go in the medulla the higher the concentration is in the medulla. You got a high concentration or high solute concentration in ... in gradient in the interstitial fluid of the medulla you know ... how does that high saw you how did those I saw you ... levels get there and how did they stay there there's two ... water called counter-current mechanism that are involved ... with a countercurrent just refers to fluid flowing in ... opposite directions the counter-current multiplication ... method refers to the fluid first flowing downward in the ... descending limb of loop of henle and then flowing upward ... again in the a sending them. Okay this is what is in charge of establishing or setting up ... the high solute levels and the gradient okay so this creates ... very high solute levels in the interstitial space of the medulla. It's primarily due to sodium chloride symporters that are in ... the thick ascending limb of the loop of henle let me go back ... to some of those pictures and see if I can show you this. Counter-current multiplication and the high solute levels in ... the interstitial fluid of the medulla are primarily due to ... notice in hearing green see the sodium and chloride that ... are being reabsorbed here that's due to a sodium ... chloride symporter that's in the thick ascending part. Of the loop of henle okay so that's creating high and high ... amounts of sodium and chloride in the interstitial fluid ... levels is what's called urea recycling okay notice here ... with the white line that says urea you have high amounts ... of urea that are constantly being reabsorbed from the ... collecting duct and they're being at least temporarily put ... into the interstitial fluid and then they're being actually ... drawn into the tubules so you have constant reabsorption ... here it goes into the two bills then it travels along the two ... bills only do get reabsorbed again so. The net result of all of this is high amounts of sodium ... chloride and high amounts of urea at all times in the ... interstitial fluid of the medulla and the deeper you go in the ... end of the medulla the higher the levels of urea and sodium ... chloride you're going to find there. The other mechanism is called counter-current exchange that ... involves the counter-current flow through the Vasa recta all ... right again the Visa recta are the blood vessels that run ... alongside of the loop of henle okay and they're going to ... know there they go in opposite directions as well ... and what they basically do is there going to be able to ... deliver oxygen and nutrients to the cells that are in the ... medulla in order to allow those cells to survive. But without washing away the high solute gradient in high ... solute levels that you have set up there with the first ... mechanism okay so another words it's a way of delivering ... needed materials to the medulla without washing away ... the solute levels another with Soviets and other words going ... to maintain the high solute concentration and Grady. This is a pretty good summary slide of the three physiologic ... processes and what's happening we're okay let me ... just highlight some of the you know some of the main points ... from this again up here in light orange. Corresponding over here you have the renal corpuscle and ... again that's where the filtration step is going to take place and. You know depending on if you're a woman or a man your ... glomerular filtration rate is going to be somewhere ... between 105 to 125 milliliters per minute okay what kind of ... things get filtered will water gets easily filtered and then ... most of the solutes in your blood get easily filtered except ... for you know medium and large-sized pro they're not ... going to get sold. Buy as you go into the dark orange you're coming into the ... proximal convoluted tubule again I think the real ... take-home message with the proximal convoluted tubule is ... that where most of the reabsorption takes place. Again just to reiterate 99%. Of your filtrate is going to get reabsorbed and roughly ... two-thirds of that reabsorption happens in the proximal ... convoluted tubule and the cells there are specially ... designed with microvilli to increase their surface area to ... make it easier for that reabsorption to take place. If you were to check the concentration of the urine at ... the end of the proximal convoluted tubule it would be ... about 300 milliosmoles per liter which is still roughly the ... same concentration that you would have in the blood okay ... go into the loop of henle or the nephron loop as they're ... calling it here there's still a lot of reabsorption taking place ... again the descending limb is always going to have you ... know it's how it's going to be very thin there's a lot of ... reabsorption are taking place as you turn the corner and go ... into the a sending them remember there may be a sick ... part to it and generally the thick part is going to be less ... permeable than this in Paris. By the time you're at the end of the loop of henle the ... tubular fluid is going to be a hypotonic relative to your ... blood in other words the concentration as you're right ... about here is going to be about a hundred to 150 million ... moles per liter. You're then going to go into the distal convoluted tubule ... and then you're eventually going to go into the collecting ... duct okay you know the distal convoluted tubule and the ... collecting duct is where you start to get into the facultative ... water re-absorption not going to be able to be controlled ... through the effects of antidiuretic hormone and then ... also through the effects of aldosterone. Notice to they also mention here calcium as I had pointed ... out parathyroid hormone is going to act on the distal ... convoluted tubule and when it's around its going to ... promote calcium reabsorption. And so you know by the time you reach the end of your ... you're collecting duct down here the concentration of the ... urine is going to be very dilute you know about 60 ml to ... moles per liter if there's no ADH around. Versus if you do have ADHD around your going to have a ... very concentrated urine you know around 1,200 ... milliosmoles per. All right let me shift gears now and talk about some of the ... ways that you evaluate kidney function. You know at least these are things that you might see in a ... hospital setting. Diabetic kidney function increases in the glomerular ... filtration rate usually result in an increase in urine ... production so as a GFR goes up you'll make more urine as ... the GFR goes down you'll make less urine however as ... we've seen there's mechanisms that control ... reabsorption and you know as well as secretion and that's ... going to influence what your final version of the urine is ... going to be like. You know on a daily basis typical normal urine output is ... about 1 to 2 okay again you have tremendous amount of ... water that are beat that are showing up in the filtrate ... about 180 L of water are showing up in the filtrate on a ... daily basis but about 179 or 178 of those leaders get ... reabsorbed so that you should only have a urine output of 1 ... to 2 liters per day. Over here you can just kind of read through this but this ... shows you some of the normal characteristics of urine ... that you'd expect to see. Your analysis is probably the most common urine test they ... do you know you can you can take some a sample of ... someone's urine you can send it away to a lab to get the ... formal urinalysis done or you can do what's called a dipstick ... urine where they put one in you know they put this little ... stick in that can measure you know some of the substances ... that are in the urine and can measure like the pH of urine ... and things like that. Urine is primarily just water you know even when you ... have a DH around urine is still going to mostly be Water by ... definition you know what are you going to find in the urine ... well by definition you're going to find substances that got ... filtered or that got secreted but that didn't get reabsorbed ... okay so that should make sense now I'm if disease ... Alters metabolism a kidney function you might start to see ... things you know present in the urine that you are nearly ... wouldn't see or you'll see it in abnormal a mouse. Urine should be sterile so you shouldn't see bacteria in the ... urine albumin as you know is like your most common ... protein that you have in your blood you should not see that ... in the urine if urine is doing anal if you're doing your your ... job with reabsorption of glucose should not be in the ... blood right again glucose gets into the filtrate no problem but ... all of the glucose should be getting reabsorb. White blood cells that can be an indicator of infection red ... blood cells that could be due to damage of the filtration membrane. Or it could represent something like bleeding later ... on like if you had anal bleeding from an irritation from ... like a kidney stone for example to the ureter or you ... had bleeding inside of your bladder that could put red ... blood cells into your urine. The other most common test done to evaluate kidney ... function I think I already mentioned it before are ... actually some blood tests that they run and that's called the ... vun in the creatinine levels all right these are ways to it to ... test your blood as a measure of how well your kidneys are ... performing the blood urea nitrogen measures you know ... nitrogen wastes that are in your blood from the the ... breakdown of amino acids again amino acids if you ... remember there's 20 different amino acids in your body ... every amino acid contains a nitrogen group so when you ... break down your amino acids. You're going to produce some urea as a waste product and ... you can actually measure blood urea nitrogen if I ... measuring that that's going to give you an indication of how ... well your kidneys are doing in terms of getting out of urea ... out of your body no remember your kidneys will freely filter ... the urea and then they end up reabsorbing about half of the Greer. Creatinine on the other hand that comes from the ... breakdown of creatine phosphate in skeletal muscle. Creatinine is I mentioned before is freely filtered so ... creatinine makes it through the filtration step very easily ... and then the creatinine doesn't get reabsorbed at all ... so another words Whatever Gets filtered for your ... creatinine is going to end up in your final urine so it's kind ... of a way at looking at directly at the filtration ability of your ... kidneys without. You know having to think about whether reabsorption or ... secretion have. Alright finally I'm going to kind of leave the kidneys behind ... and talk about the other parts of the urinary system I know ... I've been going off on the kidneys that's really because ... that's where all that hardcore physiology takes place but ... obviously you know the other parts of the urinary system ... are important mostly to collect urine and then take it out of ... your body right so connected to your kidneys are going to ... be your ureters are your ureters about 25 to 30 cm ... long they originated on your an intended area of the kidney ... known as the hilum that I mentioned before the ureters ... then travel down and they connect to your bladder okay. From the bladder as you know you then have a urethra of the ... urethra is about 4 centimeters long and women about 20 cm ... long in men you should remember from the ... reproductive system chapters that the urethra is divided into ... three parts in a man right you know the first part you have or ... the I should say the the part as you're leaving the bladder ... is going to be called the prostatic urethra then you get ... into the short part called the membranous urethra which ... also known as the intermediate urethra in the ... final part of the urethra is called the penile urethra or the ... spongy urethra. The ureters transport the urine from the renal pelvis of ... the kidneys to the bladder using peristaltic waves are ... right there is smooth muscle layers in the wall of the urine ... actually the way that the smooth muscle is organized in ... the wall of the ureter is actually the exact opposite ... from what you saw in your GI tract if you remember with ... your GI tract you usually have an inner circular layer of ... muscle and an outer longitudinal layer with the ... ureters it's just the opposite you have an inner longitudinal ... layer of muscle and then an outer circular layer but those ... muscle layers can contract and they can actually create ... peristaltic waves that help to move the urine along from the ... kidneys towards the bladder all right you know gravity also ... I helps to keep the move the urine moving along now when ... the ureters connect with the bladder there's actually no valves there. So it does raise the possibility. That urine could move backwards from your bladder ... into your yours okay and that actually can happen that's ... known as a vesicoureteral reflux okay vesicoureteral ... reflux means that you're in is going backwards from the ... bladders it from the bladder into you you're okay and that ... can be a bad thing because when the urine sits around for ... too long or if it starts to go backwards that can set up a ... situation where bacteria will colonize and you can get a ... urinary tract infection really easily okay you know one of ... the reasons why the urine is sterile is because of urine flow ... in the urine constantly flushing out your system if the yarn ... moves more sluggishly or if it starts to move backwards it ... can sit around longer and bacteria can start to colonize ... it and you can get a urinary infection now the reason why ... in a normal. Person know that the urine ... doesn't go backwards in the ureters. Is because of the angle that the ureters attached to the ... wall of the bladder okay the ureters come in. At an angle such that when the bladder fills up with urine it ... will sort of naturally compressed the openings of ... the ureters so that you're there so that urine can't go ... backwards in the urine so even though there's not ... strictly speaking of valve there. The way that their position the way that the ureters attached ... to the wall kind of creates. You know sort of a natural valve that prevents the urine ... from going backwards. What are the thing I wanted to mention before I go away from ... this picture is unnoticed you do have urethral sphincters ... just like you had anal sphincters okay remember the ... anal sphincters from the digestive system chapter ... there in charge of controlling defecation the urethral ... sphincters are in charge of controlling urination or the ... fancy name for urination is micturition and I'll talk about ... that on the next slide but noticed you have an internal ... urethral sphincter right here that's. Made up of smooth muscle and it's going to be involuntary. And then right here. You have an external urethral sphincter that's going to be ... made up of skeletal muscle and it's going to be volunteer. And when you do urination. It's really very similar to what you did when you did ... defecation alright I'll come back to this picture and talk ... about this more in the in the next slide so let me go on to that. The bladder you know it's a it's a hollow distensible ... muscular organ with a capacity that averages about ... 700 to 800 ml if you look in the wall of the bladder you're ... actually going to find rugae just like you found in the wall ... of your stomach and that's what's going to allow the the ... bladder to distend when the lad when the bladder is fully ... distended with urine does rugae essentially disappear. I'm deactivating the platter you know that's known as ... your ignition issues inside that's enough in his urination ... or micturition okay and the process of micturition involves ... a combination of voluntary and involuntary muscle ... contractions okay when the volume of urine increases in ... the bladder there are stretch receptors that send signals to ... a Nutrition Center that sit in your spinal cord that Jen that ... then triggers the micturition reflex Okay so. Let me go back to that picture and kind of tell you what's ... What's Happening Here. Okay so. Here's that picture again. Let's suppose your bladder is empty right there's no urine in ... your bladder when your bladder is empty there's going ... to be a reflex constriction of the internal urethral sphincter ... another way to this is going to be contracted. The external urethral sphincter is going to be ... relaxed it's going to be open okay so that's what happens ... when you don't have to pee when your bladder is empty okay. When the bladder starts filling up with urine. The situation is going to shift. And what's going to happen is the internal urethral sphincter ... is going to become relaxed. And the external urethral sphincter is going to become ... constricted and basically what happens there is you have ... just shifted the control from something you don't have any control over. Do something you do have control over so you've you've ... caused the external urethral sphincter now to contract and ... that again is going to be a skeletal muscle and you're ... going to have voluntary control over it so you know ... now you know hopefully you can find a bathroom and you ... can then urinate because you have voluntary control over ... the external urethral sphincter. After you empty your bladder the control will then shift back ... to the internal urethral sphincter another words then ... the internal urethral sphincter will constrict and the external ... urethral sphincter will die later will become relax. And you know and child heard you basically learn how to ... initiate and stop that reflex voluntarily by controlling the ... contractions of the external urethral sphincter. Do you rethread self again you already learned about this ... in the reproductive system chapter you know in a female ... the urethra is just dedicated to carrying urine but in a male ... the urethra is dedicated to carrying both urine as well as ... carrying a scene. Waste Management in other body systems again one of ... the main functions of the urinary system is to get rid of ... body waste materials especially nitrogenous waste ... such as urea or ammonia or things like that okay. Other organ systems do play a role in in processing waste ... and things in the next chapter will talk about buffers buffers ... are chemical pairs that are able to quickly adjust the pH ... of your body so that it doesn't get too high or too low of ... blood of course plays a role in transporting waste products ... throughout your body the liver is an important place that can ... do you know the Weaver deliver can do a lot of ... chemical reactions and can convert gif. Compounds into other compounds so it plays a role ... there I can recycle substances as needed. The lungs as I mentioned a play an important role in ... adjusting CO2 levels in the body that can also adjust ... oxygen excuse me water levels and heat to some extent. Are sweat glands they can adjust you know your body ... temperature that can also adjust to a lesser extent water ... levels in the body CO2 in small amounts as well as salts ... and small amounts of urea and then the GI tract is ... important for getting rid of. You know solid undigested waste material that your body ... decided that it didn't want as well as small amounts of CO2 ... water assault in. Development of the urinary system this is this is the way I ... like it short and sweet the kidneys develop from ... intermediate mesoderm alright nuff said Aging in the urinary ... system after age 40 your kidneys don't function as well ... so you know you can start to see build ups in your body of ... waste products that you ordinarily maybe would have ... gotten rid of or you have problem is you know ... controlling your blood pressure as effectively. Common problems that you can see as you get older ... incontinence going to not being able to hold on to your ... urine losing a little bit of urine. You know when you know between. Urine episode urination episodes urinary tract ... infections can become more common polyuria. That means you know urinating in larger than normal ... amounts and other would your retaining your urine so that ... when you do urinate you urinate in larger amounts than ... normal nocturia means having to get out of bed at night to go ... urinate you know as you get older and as you don't empty ... your bladder as effectively you'll probably then have to ... urinate more frequently at night. Increase frequency of urination as a mention dysuria ... refers to painful urination that can be caused by different ... factors that can be caused by infections and other issues I ... retention I mention is, hematuria refers to bloody no ... blood in your urine that can be caused by different things that ... could be cause to like a kidney stone kidney stones ... scraping the inside of like the renal pelvis or the inside of ... the ureters and that creates blood in your urine or can be ... cut caused by things like a bladder tumor that's maybe ... bleeding and that's putting blood in your urine. Acute and chronic kidney inflammation you know what ... can be caused by stones that can be caused by urinary tract ... infections renal calculi that's just a fancy word for kidney stones. and then prostate disorders or cancer we already talked ... about those in the reproductive system but those ... become you know obviously more common as you get get ... older in a man. All right I think that's finally it this was a fairly long slide ... wasn't as long as the digestive system chapter ... though so I guess that's some good news again if you have ... any questions please don't hesitate to contact me and ... that's pretty much it so good luck and I will talk to you later bye.