hi welcome back to educator calm this is the lesson on the urinary system the functions of the urinary system is not just as simple as making urine and getting rid of it I mean that is the primary function it's the removal of metabolic wastes that's really what urine contains solid waste of course would be in the fecal matter which is part of the digestive system in terms of getting rid of it but here is is all about filtering blood and getting rid of metabolic wastes out of your bodily fluids in addition to that you have the regulation of blood volume and blood pressure your kidneys actually secrete hormones in response to how much blood is flowing through them the pressure either the you know lack of fluid or too much fluid and that has an effect on your blood pressure and blood volume it also regulates plasma concentrations of various electrolytes various minerals like sodium potassium chloride etc because it's going to get rid of more of those or less of those through urine depending on how much you have and it also helps to stabilize blood pH in addition to getting rid of stuff like sodium or hanging on to it hanging on to H+ or getting rid of H+ these hydrogen ions that has an effect on pH in addition bicarbonate ions which has an effect on the alkaline levels so if you know enough about pH you know hanging on to this would actually make the blood slightly more acidic getting rid of this would actually make the blood slightly more basic and the the normal pH for blood in the human body is seven point four on the pH scale that's slightly basic it also conserves valuable nutrients you want to hang on to certain things in your bloodstream and not get rid of them and that comes down to kidney function so we look at the different organs and tissues the urinary system there are four main players here's a little drawing of it you've got the kidneys of course they look like kidney beans this is the left kidney this is the right kidney the left kidney is ever so slightly higher the right kidney is a little bit lower because of the liver kind of hanging down over it so you know it's normal with two kidneys there are the ureters which of these tubes that take recently made urine out of the kidneys to a temporary storage spot known as the urinary bladder just calling it the bladder is not sufficient in anatomy because there's also the gall bladder so you want to specify that this is the urinary bladder and then the urethra the urethra is that tube that finally takes urine out of the body and it is of course longer in males shorter and females I'll discuss that more later all right so when we look at kidneys these amazing organs that actually make urine you do have two kidneys on either side of the spine between the thoracic vertebrae at the bottom of the thoracic curvature so number 12 where your last ribs are found and down to about the third lumbar vertebra which means that they're only partially covered by your ribcage just just the top portion has some ribs going just posterior to it and your kidneys actually are very much a posterior organ there's this term kidney shot if someone you know hits you right back they're right under the ribcage and that kind of impact could definitely damage kidneys that happens in contact sports often but the left kidney is slightly superior slightly higher to the right one they are held in place by surrounding connective tissue and that surrounding connective tissue includes the peritoneum and it's it's a nice wrapping around abdominal organs that that keeps them in place and there's other neighboring organs that help keep them in place their reddish brown the reddish this of course because of the high blood flow there's a lot of blood going to your kidneys every second of the day they're about 10 centimeters long five and half centimeters wide and about three centimeters thick with a mass of about 150 grams each so here are the the major parts let's label these so the renal cortex renal cortex you see that right here as with the adrenal glands or any other organ that has the term cortex that means the superficial outer part of it so the the renal cortex you're going to see a lot going on in the next few slides in terms of how the filtration process gets started the renal medulla or medulla some people pronounce it that way that's a bit deeper just like with the adrenal medulla so you can see that these little areas that kind of look triangular that's really where most of the module is going on and those are called renal pyramids because they do look pyramidal triangular so here's a renal pyramid real pyramid renal pyramid so those make up most of that medullary layer in the kidneys and this is of course a cross-section a frontal section or coronal section through a kidney from the outside you would not see the pyramids and you know seeing that medulla so you'd have to cut into it to see and then you have these two areas they're each calluses or calyxes major and minor so once you have development of urine it comes out of the medullary area into what are called minor calyxes and all of the minor calyxes lead to major calyxes these are the major calyxes here and then it goes into what's called the renal pelvis so the renal pelvis I use yellow for like the calyxes and and here these are the calyxes and then the renal pelvis is this collecting area right in here and this other term the hilum is kind of that exit region of the kidney through which the renal pelvis empties into the ureters so renal pelvis is actually at the the medial side of the kidneys because the kidneys kind of point towards each other and the renal pelvis --is feed into the ureters which of course then go into the ladder so blood flow to the kidneys amazingly in a healthy individual over one litre of blood flows through kidneys each minute of your life that's incredible to think about because the average person has about five liters of blood in their body or ten pints so yeah it's amazing to think that 20% of that is is constantly just there every minute going through your kidneys so they're doing an amazing job of filtering blood they receive blood through renal arteries the term renal always applies to the kidneys so here's these different parts here the segmental arteries are right here so the segmental arteries actually branch off of the major renal artery into the kidney the inter interloper arteries let me show you those they actually end up going into each little lobe so here here here here here all of these are interloper arteries which branch off of of the little segmental arteries here the arcuate arteries finally take blood branching off of the interloper mobile sorry lower arteries all the way up to the more superficial cortex regions so here and here and so on you're going to see those arcuate arteries and then finally those branch off into these tiny little capillary bundles you can call them afferent arterioles that lead to the capillary bundles because number arterioles branch off of arteries slightly smaller and then they lead to capillaries so afferent arterioles because they're going to these little filtering regions in the kidney those all these up here these afferent arterioles get super super tiny to the point where they're microscopic and they form little capillary bundle was called glomeruli and you're gonna hear more about those on the next few slides so the afferent arterioles i'm not going to code those those are all in here in the the cortex of the kidney and they branch off into millions of little bundles of capillaries so blood leaves through the renal veins so you have this blue little tube here the renal veins take blood out of the kidney the blood that hasn't been filtered out to make urine and of course blood flow is going to be regulated by nerves they're called renal nerves alright nephrons these are the little filtering units of the kidney this is where all the action happens so they are microscopic tubular structures in the cortex of the kidneys at least that's where they begin that do the filtering of blood and production of urine here's a model of what it looks like because it's in three-dimensional space some of the precise arrangement of where these tubes are kind of Criss crossing can vary and you're going to see that represented in future slides in this lesson where sometimes this little tube you'll is actually slightly off to the side over here but the names are still the same based on the order in which fluid is moving through there so 1.25 million nephrons per kidney Wow amazing to think about that you're going to have two and a half million total microscopic little amazing filters getting the job done so first off the glomerulus okay the glomerulus is this little bundle here it's a bundle of capillaries and they go into this little capsule and then you have certain items water ions etc moving across into the capsular space which then leads to these little tubes these little tubules so the Bowman's capsule is act so I'm going to label actually glomerulus that's I'm gonna check mark there because that's in red the Bowman's capsule named after dr. Bowman I presume is this right here and together you could call them together the glomerulus and the capsule around it a renal corpuscle so I didn't actually write that but this thing here that little box that's describing the interaction between those two renal corpuscle so the Bowman's capsule that leads into this here that's known as the proximal convoluted tubule its twisty turny proximal to where this began and then later it'll be distal more more distant proximal convoluted tubule or PCT so this right here keeps going he's gonna go and leads to the loop of Henle o Henley another scientist I presume that's what's going on here so this is the loop of Henle and there's actually two parts to it there's the descending limb of the loop and then there's the a sending limb going back up and then the distal convoluted tubules what's let's use blue for that one again so the DCT is a little bit more distant here it is and then eventually we get into some other parts this is the the collecting tube which has some ducts that lead into what's called a papillary duct and of course that's going to lead deeper and deeper deeper into the kidney and by the time you get down here it's urine and that you're in collects from all these millions of different nephrons together going out the ureters to the bladder so you can hear more about that in a few slides so how does a stuff get filtered out of a glomerulus and and plural is glomerular so a glomerulus is a bunch of capillaries of course and I didn't label this on the last slide so I'll tell you here this is the afferent capillary going into here into the what's what we call the glomerulus and this would be the efferent one just like with nerves going to the brain out of the brain afferent neurons efferent neurons is the same idea here afferent defferent they are fenestrated and if you watched the blood vessel lessons previously a finestra that that means window so instead of solute little microscopic particles having to go through the barriers of these capillary wall cells they don't just go through little borders of the cells they're actually in each cell are little holes essentially and the fenestrated capillaries make it very easy for stuff to quickly pass through that small enough to fit through so blood pressure forces water is that small enough and small solutes across the membrane through the fenestrated capillaries and into the capsular space the Bowman's capsule here and some important nutrients like glucose fatty acids amino acids and vitamins can also pass through you don't want to let go of all those things because especially if you're if you're low on them in that moment you you need these things in your bloodstream to supply these nutrients to your cells there is a way to get that stuff back in your bloodstream which we're going to cover a little bit later it has to do with them being reabsorbed into the proximal convoluted tubule ah the proximal convoluted tubule so right after we leave the glomerulus and a mixture of water solutes and maybe some of those slightly larger organic compounds are coming through here here we're now in the proximal convoluted tubule or PCT it is the first segment of this renal tubular system and it's lined with simple cuboidal epithelium so if you remember back to the tissues lessons we went over what simple cuboidal epithelium looks like if you were to take a cross-section of the PCT you would see kind of cube looking one cell layer thick cells and of course they're all going to have their own little nucleus so here's that rounded cuboidal epithelium this would be called the lumen within this tube and reabsorption of nutrients happens here and what's meant by that is you have water and solutes coming through here and that's eventually going to be urine but at this point as you go through this tube you can actually suck out because of osmosis in diffusion some of the nutrients ions water and plasma proteins that happen to come in there that you want to hang on to so as you go through the PCT you're going to have the release of these items into the peritubular fluid fluid that is around here speaking of which if you were to look at a highly detailed version of this diagram you would see your your venous blood or just capillaries in general that aren't part of the glomerular complex just coming around these tubes and so you can get that stuff back into your bloodstream once it's exited this tube you'll and that's good you don't want to let go of ions that you're low on or plasma proteins that are important to have once you have some of that reabsorption occurring through this PCT you're going to end up in the loop of Henle and this is actually under exaggerated it should be much longer some of these loops go very deep into the medulla of the the kidney so it's found in the medulla area of the kidneys and like I mentioned before here is the descending limb and the ACE ending limb of the loop of Henle and so what's going on here well you actually have active transport occurring in this section I mentioned how diffusion and osmosis would drive reabsorption here that's a passive process but active transport actually can occur here you're going to pump out some sodium and chloride ions which is going to move water out of the tubules and start to make urine more concentrated you don't want to let go of too much water in your urine and water movement out of that loop helps concentrate the tubular fluid as the fluid moves through here next up the distal convoluted tubules the DCT which is here and here in kind of this salmon pinkish color it differs from the PCT that was in kind of this purplish because of a small diameter smaller than the PCT and lack of microvilli you actually would find some microvilli associated with that cuboidal epithelial layer and so what does the DCT do it's important for three basic processes it will actively secrete ions acids drugs and toxins so your kidneys are actually helping out with you know getting rid of drugs and toxins the liver of course plays a big part in that too but your kidneys are gonna help with this that's great selective reabsorption of sodium and calcium ions based on your needs depending on your calcium sodium levels in your blood that's going to determine how selected that absorption is and selectively absorbs water so it's just finalizing what's going to become urine how much stuff you're going to let go of how much stuff you're going to hang on to finally it's the collecting system so we've already talked about this renal corpuscle the glomerulus and the Bowman's capsule here's that PCT the loop of Henle the DCT and then you finally get to what's called the collecting system so there is some final filtration that happens here secretion and reabsorption i'm going to talk more about what these terms specifically mean on the next slide but now concentrated urine passes through the collecting duct this purple region which merges into papillary ducts so the papillary ducts get all the different collections that you're in collected from the different nephrons in this region and finally empty into what's called the minor calyx which I mentioned before the minor calyx is lead to these major calyxes these kind of hallways that lead urine into the renal pelvis and finally out into the ureters alright so summary of urine formation three terms that you need to keep in mind three basic processes and the first one is filtration filtration that's mainly what's going on with the glomerulus that collection of capillaries and the Bowman's capsule so blood pressure forces water and some other solutes into the Bowman's capsule to start it off so that's the initial filtration from out of your blood then reabsorption reabsorption is getting the stuff that you want to hang on to out of that tube so that it doesn't escape through your urine so water and solute are removed from the tube you'll you know the the PCT etc and go into the peritubular fluid outside of those tubes important fluids and nutrients are reabsorbed into the blood through active transport in osmosis so as blood leaves the kidney that stuff is not going to escape through your urine and secretion solutes are transported from the peritubular fluid back into the tube you'll that that's the final chance to to get stuff that you do want to get rid of out of that pair of tubular fluid where stuff's been reabsorbed and it can go back into that distal part of the tube you'll and then into the collecting system this is necessary to do because filtration alone is not enough to get unwanted wastes out of the plasma so if we didn't have the secretory ability the amount of wastes we get rid of every time we urinate would not be sufficient to maintain homeostasis urine it's about 95 percent water sometimes is 93 percent sometimes it's 97 percent this is an average for most of the time but eight what's the other five ish percent what else is in it so here are some main players that are going to be found in urine urea it's very abundant in terms of how concentrated it is in urine versus the other things it comes from the breakdown of amino acids that's happening constantly in your body it's a way to get that waste out and amino acids emember the building blocks of proteins a lot of protein stuff going on in terms of the decomposition of proteins in your body you need to remake proteins they don't last forever creatinine comes from the breakdown of creatine phosphate which is the muscles and if you watch the muscular lessons you learn about how creatine phosphate can aid with re making ATP quickly in muscles which is important uric acid for from the cycling of nitrogenous bases of RNA your making RNA in your cells constantly throughout life so uric acid is going to be from this RNA waste and what makes your in yellow euro billon is a term also some people refer to it as euro chrome euro chrome literally means color of urine so euro billon a byproduct of the breakdown of bilirubin that also influences the color of fecal matter but yeah the reason why urine is yellow is when Billy Ruben is broken down and this comes from the breakdown of red blood cells from from heme groups in RBC's that by itself is yellowish and so it makes up enough of of urine to give it that yellow color sometimes urine is a bit more clear and that typically means the specific concentration of water is just much higher so if your water is clear that means you're super hydrated you have so much water relative to other times that you're getting rid of that water you've taken in so much water you don't need that much or if your urine is clear it could mean you're drunk because you learn about this in a future lesson if you look at the alcohol lesson the ADH antidiuretic hormone that ability to hang on to water in the kidneys is definitely damaged by alcohol intoxication and the amazing thing about urine is even though you know some people will find it disgusting there's nothing that's actually harmful about it in terms of bacteria it's sterile I mean unless you have a urinary tract infection but your in itself is sterile when it comes out of the body there's no bacteria in it you may have seen survival shows or you know a list of things to do if you're stranded on a raft in the middle the ocean or in a desert where there's no water no moisture if you want to prolong life one of the things you can do is drink urine because it's a way to get those fluids back into your body that you just let go of and eventually if you just keep doing that you're going to stop making urine because you're not introducing any new water in your body but even though that's disgusting to think about it can keep you alive for a little longer but if you urinate into let's say a bottle and you wait a while let's say you don't drink it right away you just wait hours and hours and hours in that bottle that you just urinated in there was bacteria and your urine is warm has nutrients bacteria you're going to start eating stuff in there and dividing so if you do leave the urine in the container that can introduce a bacterial infection into your body but you're in itself sterile the ureters that is what is actually taking urine down into the urinary bladder it's a pair of muscular tubes here in yellow that connect the kidneys to the urinary bladder firmly attached to the posterior wall remember the kidneys are found in the back portion of your abdominal region so the tubes that are coming out of it are going to be right there three tissue layers similar to what we saw with digestive system stuff inner mucosa that's actually adjacent to the lumen that's where urine is going to be muscular layer because you do have to help move along the urine and the outer connective tissue that's going to help keep these tubes anchored to the neighboring tissues and organs peristalsis we've seen that term before with moving your digestive stuff through also through moving through the fallopian tube OVA eggs waiting for sperm peristalsis this wave-like muscular contraction actually happens here it sweeps urine down through these tubes it's not just gravity taking them down the the sweeping muscular action of peristalsis actually gets urine constantly into the bladder your urinary bladder hollow muscular organ that is a temporary reservoir for urine of course it can hold as much as one liter of urine so think about one of those soda bottles it's two liters that's that's a lot of urine that's when your really really really gonna have to go because just as much as 200 milliliters of urine you know 20% of that it is going to initiate some urinary reflexes that are going to start preparing your body for for urinary time the rugae so when we look inside of the urinary bladder you're going to see folds similar what you see inside of a stomach so the rugae those little folds as the the urinary bladder expands as a holds more urine those rootbeer less obvious because of the stretching mechanism of the bladder the trigon is this triangular feeding area that urine is going to be collected into and then eventually emptied into the urethra the border though between the trigon and the urethra is the internal urethral sphincter sphincter is always a muscular kind of doorway from one part of a tubular passageway to another and in this case this is involuntary you do not have voluntary muscular control over this this is going to open up as stretching happens in the inferior parts of the urinary bladder so that need to urinate as the the internal urethral sphincter relaxes and lets more urine out that's that's when you need to go so the urethra is that final tube leading out of the urinary bladder and then out of the body so it extends from the neck of the urinary bladder and finally exits out longer in males than in females and you can see from this image here when you take into account the external genitalia of men the urethra can sometimes be eight inches long because you're also including the internal part prior to it entering the penis that that you know empties out of the bladder so if you take into account you know P is length in men the urinary tract is going to be longer in females it's only about that big because once you come out of the bladder you're going to hit the external genitalia of females and so the UTI likelihood your inner tract infection likelihood is actually much more common in females which I'm going to talk more about later the external urethral sphincter is what is the final muscular doorway that's not letting urine out you have voluntary control over that similar to the external anal sphincter so voluntary control you know you can hold that to a point but once your bladder is filled up you know - that one liter max and urine is creeping into the urethra that the need to let it go is going to happen and micturition is the technical term for urinating and the micturition reflex that's going to happen as you get stretching in the bladder as your neurons connect to the bladder get sense of that stretching it's going to send a signal to brain and then send a signal back down to the voluntary muscles when you actually actively urinate but remember there is involuntary parts - as the involuntary muscles relax the need to actually finally let it go is going to happen so urinary conditions and disorders like I mentioned a bit ago UTI urinary tract infection much more common in women because it's typically a bacterial infection and if you think about the the urinary tract of a female being just this big the ease for bacteria or ability to take over this region happens much easier so the dividing the bacteria can quickly invade that tube if the tube is this long it's less likely that the bacteria are going to be able to conquer that tube and cause significant urinary tract infection it does happen in men don't get me wrong but it's just more common in women kidney stones kidney stones happen in men and women I've heard that they happen slightly more in men I don't know if that's dietary differences on average but kidney stones can happen for a variety of reasons it's basically a collection of hard deposits in parts of the kidney over time and it's they're so hard and so large relative to the size of the tubules kidney that they cannot get out completely through the urethra and they do get backed up you can see an image here these are actually fragments of kidney stones very tiny you can see that at most they are half a millimeter in diameter so very tiny but if you think about how tiny the tubules are leading urine out of the body you can see how they get stuck and of course you're going to get a back up there very painful one amazing way that you can get rid of them that doesn't require surgery is they've learned that if you project soundwaves at the kidney you can sometimes shatter these kidney stones into tinier bits that can naturally be eliminated from the body which is amazing to think about so the technical term is renal calculi the renal calculus would be one kidney dialysis is accompanied with renal failure so if somebody's kidneys are just not getting the job done to filtering their blood you will hook them up to a machine that basically filters their blood for them and since the kidneys also have a lot to do with stimulating the making of red blood cells and other cells in the the bone marrow drugs that help make red blood cells will also be introduced into the body in addition to the filtering of their blood and this is a temporary solution kidney dialysis does not cure kidney failure it will prolong life but the need is for a kidney transplant you can get a transplant from a donor who is deceased and and I've heard that that's 85% effective on average if you get a kidney from a relative who's alive your likelihood of success and prolonging your life is more like 90 something percent in terms of adding years on your life and it being a successful transplant but people who do get kidney transplants they need to take immune suppressing drugs because even if it's your brother that's donated one of his kidneys or a cousin she's donated one of her kidneys that's not your kidney and the precise protein makeup on those kidney cells is not close enough to fool your body into thinking oh yeah it's our cells so you actually would have to take immune suppressing drugs to kind of calm down your immune systems response to that tissue introduction and that makes a person who's received a kidney transplant slightly more successful to other illnesses but it's worth it prolonging your life glomerulonephritis so nephritis basically means like infection affecting the the nephrons and it has to do with the glomerulus coming into that region so the amazing thing about this is the infection is not in the kidney itself but some infection in the body is now affecting the kidney negatively and the reason why that negative impact happens is with certain infections in the body you're gonna get a buildup of a lot of different antibodies in response to antigens that's part of your lymphatic systems ability to beat the illness but that buildup can actually when it gets into the glomerulus that can really affect blood flow out of the glomerular into those corpus schools and into the the Bowman's capsule specifically so this is an infection that is negatively impacted the filtration ability of the kidney and then incontinence this is the inability to fully control when you're going to urinate and this tends to happen more in older people as they age the the muscular tone in terms of like keeping urine inside is not as it's not as good also you know strokes and Alzheimer's can have an impact on that ability to control urination and it also can happen in in pregnant women to the the baby is going to take up a lot of space in in that region of the abdomen and it can not only press on the bladder but also stretch out some of those urethral muscles makes it hard to hang on urine during pregnancy for some women so thank you for watching educator com