Transcript for:
Urinary System and Kidney Anatomy

hi everybody and welcome back today we're going to be looking at the urinary system please note that in this video we're going to be looking at the microscopic and macroscopic features of the kidney and in follow-up videos we will be touching on the different processes like ultra filtration and tubular secretion don't forget to like this video and subscribe to make sure that you never miss a new video so of course we need to start off with our components and the most obvious component of our urinary system is going to be our kidneys you'll notice that we have two bean-shaped kidneys one on the left and one on the right and they're slightly at an angle to one another just because we're going to fit all our organs inside of us they're about the same size as your palm and they are really important for filtering our blood the next component that we see coming out of each of our kidneys so we have one for each kidney is this tube over here this tube is called our ureter and it's really important to get the spelling right on this one because you'll see in a later label you might confuse it with another structure now the ureters are tubes that join the kidney to our bladder which is this structure down here now our bladder is a muscular bag it is where we store our urine um before urination and it can contract and relax making more or less space then finally we have this tube exiting our bladder which is the urethra and you can see why some people get the spelling incorrect why they might confuse them and so in a test or an exam you need to make sure that you're getting that spelling right lastly something that's a little bit difficult to see on this picture here but we need to know it exists is there is a structure that is sitting right here at the base of the bladder but also right here at the base of the urethra and that is something called a sphincter a sphincter is a special kind of muscle that's in a circle and essentially it contracts and relaxes involuntary which means you don't control it your brain does it for you and make sure that the urine stays in the bladder until you are ready to urinate next we're going to look at the regions of the kidney so what we've done is we've taken one of our kidneys we've cut it in half so we can see on the inside and as you'll notice there are regions on the inside and it's important to know what these regions are because they're not just structures that we would have to label but they are also locations of certain processes now the first most outer region is this lighter pink region that we can see sitting here and that is known as our cortex now to make this a little bit easier and this is often where confusion comes in i'm going to color in the cortex but essentially the cortex takes up all of this space that we see sitting on the outside of our kidney predominantly the majority of this lighter pink but you'll notice i'm not actually coloring in between these sort of fan shaped structures and the reason for that is that is another layer and they sort of overlap on top one of the of each other so that's often why they're misidentified the next region we have is just inside of that and it is the medulla now the medulla consists of almost this entire region that we see sitting on the inside of our kidney um it is sometimes a little bit confusing to identify because it actually has these fan shaped structures inside of it as well as this lighter pink which often we misidentifies being part of the cortex but remember we're doing regions here so it's almost like layers if that's what you want to call it which is a better way to identify the regions it's a layer and so that's why sometimes layers can slowly fade from one to the next the last region of the kidney that we need to be aware of is this brownie yellow area over here and this is known as the pelvis or the renal pelvis and the renal pelvis is the innermost part of our kidney it's basically where all of our collection of our fluid is going to take place so to give you a brief overview of why these regions are important they are important because blood when we look at this at a later stage is going to move from the cortex into the medulla from the medulla into the pelvis and then down and out into the urethra which is what this structure is over here now that we are familiar with the regions of the kidney we're going to move into the macroscopic structure of our kidney and remember we don't just need to be able to identify these structures we also need to be able to know what they do and their functions now let's start off with our easiest structures and that's going to be the blood vessels that are going into the kidneys the first one is this one over here this is our inferior vena cava and if you remember the inferior vena cava that blood vessel is going to be bringing blood away from our kidneys whereas on the other side over here we have our aorta which is going to be bringing blood towards our kidneys now probably in a test or an exam they are going to ask you what is the difference between these two in terms of composition like what is in the blood at this point and i think it's important to know that because this is the blood vessel that is leaving the kidneys and going back to the heart it's deoxygenated but it's been filtered which means it doesn't have any wastes in it whereas the aorta which is coming into our kidneys that is filled with wastes but it's also high in oxygen so that's another little key tip to remember when you're studying for the macroscopic structures now these two blood vessels branch down into much smaller vessels and the first vessel over here that enters into our kidney is known as the renal artery the renal artery as i said before is going to be bringing in a lot of our what we would call our wastes which we're going to learn about in our next video and but it's going to be high in oxygen on the other side of that we have our renal vein and our renal vein is going to be leaving our kidney and it's going to be taking all of our filtered blood and it's going to be returning to the heart where we're going to re-oxygenate the blood then moving into a structure which we have already identified before but we need to know where it's labeled on this picture and that's going to be the ureter you will remember from an earlier section of this segment that we looked at the ureter right at the beginning and it is the tube that exits out of our kidney and it goes down and joins the bladder lower down next we have an outer protective layer that sits on the kidney it's a membranous layer known as the renal capsule now the renal capsule is specifically there to prevent any infections that you might have in the kidney it's thin and it's membranous some textbooks identify it as a region but it's not a region it is just a structure that surrounds the outside of the kidney now let's look into the inner structures now you will notice each of these kidneys has these sort of fan shaped structures throughout and in particular this kidney on the left hand side here has one two three four five six of these fan shaped structures and what these things are are pyramids now they are essentially a collection of tubes that all flow in the same direction and because they all flow in the same direction these tubes it creates a sort of pyramid shape where you are wider at the base and then more pointy at the end now the pointy part or the part that seems to filter down into the lower area in other words if i were to just quickly label it this little area down here that is known as the papilla and the papilla is essentially where what we call collecting tubes or collecting ducts all joined together and that's essentially where we're collecting all of our filtrate our urine eventually when we get to that part and it's going to filter down and out of our kidney the next structure we're going to look at is the renal pelvis which is this sort of dark and yellow area that we see on both of our kidneys and the renal pelvis is responsible for collecting urine from each of the pyramids it's a hollow cavity within each of our kidneys and so essentially what's happening is the urine is slowly but surely draining out of our pyramids down the papilla and then it's going to end up into the pelvis which is where all of the collection of the urine eventually happens and then eventually urine will make its way down the ureter and then towards our bladder now the next structure is quite tricky to see so i'm going to actually highlight a little bit of it so that maybe it makes a bit clearer in this diagram and that is going to be what we call the calax so we just spoke about the pelvis and in these pictures the pelvis is this inner region but if you look very closely you will notice that it sort of reaches up i'm going to cut color it in in green here it reaches up to each of the pyramids and this little area here that it reaches up and extends into the pyramids is the kalax so let's actually label it so you can actually see what i'm talking about it is this structure over here um and essentially that is where all of the collecting ducts form a single tube the calax which then drains into the renal pelvis basically to make it simple the renal pelvis is the big hollow chamber that each of the kayla sees or calax for singular drain down into so essentially you have these funnels which are the pyramids they funnel down the liquid through their papilla into the calax the calax joins into the renal pelvis one structure slowly fades into the next now we move on to the microscopic structure of the kidney and what we've done is we have zoomed in on our regions first of all let's just familiarize ourselves so we know exactly what we're looking at here this section up here is going to be our cortex remember that is the outer region of our kidney then we have our inner region of the kidney which is lower down here this is the medulla it is the more um central region of our kidney and then we have this yellow structure which is microscopic so we can't actually see this the naked eye and keep that in mind if you are ever asked whether or not you can see it you can't see it um and so you wouldn't be able to see it in a dissection of a real kidney you need a microscope but this entire yellow structure that you are looking at here now including the capillary network that is wrapped around it this structure here is called the nephron and the nephron is the functional and structural unit of the kidney basically what that means is this yellow network of tubes is responsible for carrying out the function of the kidney as well as being the main structure of the kidney this is where filtration occurs through this long network of tubes now in the next slide we are going to look at all of the components and a rough overview of what they do keeping in mind in this video i'm not going to cover the processes i will do the processes in separate videos now what we've done is we've zoomed in on one of those nephrons and remember that is going to be our functional unit of the kidney it's the part of the kidney that's doing all of the filtering and so if we are going to label it it is going to include this entire structure here that we see and essentially it's a selection of tubes where they are going to carry out our filtration then you will notice wrapping around our nephron is going to be a set of capillaries and there is a larger venule that sits just above it and a arterial and if you're confused about those words please remember that a venule is basically a small vein and that would have come from the renal vein and an arteriole just basically means that it is a small artery now that small artery is going to break up even smaller and it is going to become the afferent and different arterial now it's actually really important to tell the difference between which one is which so let's just also clarify here the direction of blood flow blood is going to be coming in via the afferent arterial and it's going to exit via the efferent arterial so let's quickly label those so if we have our afferent arterial we're going to label it as this particular arterial it is and it's an easy way to remember afferent means to enter it means it's going into so why is this so important to know the difference between the two because the afferent and efferent arterials dictate what blood pressure the organism is experiencing at that time it also maintains um the filtration system that's actually happening in the kidney so the afferent and efferent arterial are essentially the arterials that go into and then out of so afferent is in and efferent is out it exits so what exactly is the afferent and efferent arterial exiting well it is this circular structure that we can see over here and it's made up of a couple of components and so the whole thing collectively together is called the mel figgian body it has quite an unusual name and some people struggle to pronounce it you can call it malfizian malpigian but it is called the mel fijian or phigian body it is also known as the renal corpuscle in a lot of textbooks so those names are actually interchangeable with one another now the malfizian body is made up of two components the first component you'll notice here seems to be this like cup shaped structure looks like a cup that structure is known as our bowman's capsule it is often considered a component of our malfujian body and so it often falls under the whole structure called the malfunction body so bowman's capsule it gets its name from the person who first um identified it then sitting inside of that cup-like structure you'll notice that the efferent and afferent arterioles seem to create what looks like a glob like a collection like a dense net of vessels and that is our glomerulus now the glomerulus is literally as i described it now a connection and a collection of blood vessels that sort of wrap themselves back and forth over one another it's a netting in sort of how it looks and basically this is where very important filtration happens why does it go back and forth over itself in other words why is it so dense why is there so many of them in there it's because you want to increase the surface area because you want to be able to filter as much blood as possible so you're going to use as many tubes as possible now leaving the malfudium body is going to be our first set of windy tubes and if you have a look here this first section is going to wind and then all of a sudden it gets a little bit thinner but this first thicker section does have a name and it is called the proximal convoluted tubule yes i know it's a very very long name proximal just means that it is close by or closest to so proximal means close and convoluted means it's a twisty tube then going down beyond the proximal convoluted tube you will notice that the tube gets quite skinny it goes down and takes the sharp turn and goes back up again that thinner section of the tube is called the loop of henle now the loop of henle is divided into two parts it is divided into the ascending and descending so ascending means going up descending means going down they have very different functions so the down part is different to the up part i will do that in another video as well as to how you tell the difference between what they're doing now i've just had to erase the big nephron label so i can fit in this next set of labels but now we're going to travel with our tube away from the loop of henle and it goes back to being this thicker tube that is also windy and it has a very similar name to the one we've heard of before this one however is called the distal convoluted tubule and distal in life sciences just just literally means like far away or the further side of it and so what they mean is it's the furthest tube away from the glomerulus and the malfunctioning body and so that's the distal convoluted tubule the final part of the tube you'll notice um actually collects down into this much bigger tube and you'll notice it has a couple of branches that enter into it and that actually means that each one of those little branches is connecting two different nephrons and this name of this particular structure is referred to as our collecting duct now the collecting duct or collecting tubule is responsible for just as its name suggests it collects all of the urine that is finally produced at the very end of this process and so what we've done is we've looked at all of the microscopic structures but we haven't done any of the functions of the different tubes which we will cover in the next set of videos at the end of every section i like to do a terminology recap because we learn a lot of terminology and biology and um it's really the basis for our understanding so let's quickly run through all of the terminology that we've learned in this video first of all we looked at the ureter which was a set of muscular tubes that exit the kidney towards the bladder the bladder is where we store our urine it's a muscular bag and then the urine is going to exit the body is through the urethra which is also a muscular tube a sphincter is a circular muscle that controls the um urine and how it moves through the tube so it contracts and relaxes and then we looked at the blood vessels associated with our kidney we had the renal vein which takes away filtered blood and we have the renal artery which brings unfiltered blood to the kidneys now attached to those slightly smaller vein and artery we have the largest vein and artery which is in this case the inferior vena cava it's the largest vein that is going to go back towards the heart and the aorta which is coming from the heart we then also looked at the kidney we have two kidney bean shaped organs in our lower back abdomen sitting above them is our adrenal gland our gland produces a few different hormones one of them we're going to focus on in other videos called aldosterone it maintains your salt then we looked at the regions of the kidney which is the cortex it's the outer region and the medulla which is their inner region we also looked at the renal capsule which is the protective layer on the outside of the kidney it prevents infection we have the pyramids which are collections of nephrons and collecting tubes normally you see six to eight maybe even a few more in some animals we looked at something called a k-lax a k-lax is um the beginning of the renal pelvis it's basically where our pyramids section into and fit into the hollow part of the kidney which links me to my next word the papilla the papilla is the tip of the pyramid and the papilla fits into the callax so let's not confuse them the propeller are part of the pyramid it's the bottom of the pyramid and the propeller slowly drain into the calax the calax then drains into this next terminology word the renal pelvis it's the hollow empty part of the kidney where urine will collect and then go down the ureters then we looked at the microscopic structures of the kidney we looked at the nephron which is the functional unit we looked at the afferent arterial which is the blood vessel that goes into the nephron and the efferent arterial which is the one that exits and they play a really important role in a few processes we looked at the malfugian body also known as the renal corpuscle which is this round globular looking structure that houses two things one it contains the bowman's capsule which looks like a cup and the glomerulus which is a set of um blood vessels that um are formed by the afferent and efferent arteriole we looked at the proximal convoluted tubule and the distal convoluted tubule so essentially the close twisty tube and the far away twisty tube the loop of henle um which was that deep little loop that the nephron takes has a very important purpose and lastly the collecting tube which is the final tube that collects all of the urine out of the kidney and takes it down into the ureters and then to the bladder as always i hope you've enjoyed this video and give me a like and subscribe and i'll see you soon bye