Urinary System

by Geoffrey Meyer, PhD

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    00:00 In this lecture, I'm going to describe the histological structure of the kidney, ureter, bladder, and the male and female urethra. These organs make up the urinary system.

    00:16 There're a number of learning outcomes that I'd like you to achieve at the end of this lecture. I'd like you to know the structure of the kidney, and be able to define a lobule in the kidney, and then understand the structure of the nephron and the renal corpuscle. And then, be able to describe the structure and function of what the glomerulus is all about, and how it filtrates the blood and forms an ultrafiltrate. We will then look at the different tubule systems that make up the nephron, and it's important that you understand how to identify each of those tubules, because it's important to relate the structure of these tubules to the function that they carry out when you learn physiology of the kidney in physiology lectures. It's also important to understand the role of the macula densa and the juxtaglomerular apparatus.

    01:24 The blood supply to the kidney is also very important, particularly, to supply to the nephron and the vasa recta. It's also important when you look at the kidney to be able to differentiate cortical and juxtaglomerular nephrons. And finally, you should be able to describe the structure of the bladder, the ureter, and also the urethra in the male and the female.

    01:55 The kidney is very important. It removes all the toxins of the body.

    02:01 These four dot points summarize the function of the kidney. It removes toxins and also retrieves back from the filtrate, substances and water that the body needs. The kidney has a role in adjusting blood pressure, an acid-base balance of all the body fluids. It produces the hormone erythropoietin and also assists in the production of vitamin D. And I want you to remember this as we go through this lecture. I'm not going to mention these last functions of the kidney except now. But I want you to be able to recall later on when I talk about the peritubular capillary plexus around the nephron that those endothelial cells secrete erythropoietin when they detect that the oxygen levels are low in those capillaries. And erythropoietin then stimulates the bone marrow to then release more red blood cells, and therefore hopefully, increase the oxygen content in the blood. And vitamin D is converted into an active form by the cells of the proximal convoluted tubule, and vitamin D is very important in bone growth, in bone development, and calcium levels.

    03:33 So although we won't mention this again, just remember these two functions, and also, remember the component of the kidney that carries out these two functions.

    03:42 It's important before we look at the urinary system, and particularly the kidney, to at least understand its growth or general structure. On this slide, there is a list of important structures. On the left-hand side, there is a diagram in the center of the kidney. And on the right-hand side, there is a diagram of the region of the cortex and the medulla illustrating the nephrons. And I want to just go through the central diagram and explain a few points about the general anatomical structure of the kidney.

    04:23 You can see a renal artery comes into the kidney at the hilum of the kidney.

    04:28 The hilum is the region where blood vessels, nerves, and in this case, the ureter, pass in or out of an organ. Where the renal artery travels in to the kidney, it breaks up into various components and then supplies the different lobes of the kidney which I'll describe shortly. Then this artery divides into an interlobar artery and travels up between the lobes, and then bends around and travels parallel to this region as an arcuate artery. And this region that these vessels have travelled through is the medulla of the kidney. These arcuate arteries then give rise to interlobular arteries that travel up through the cortex. And those interlobular arteries are going to supply the glomerulus, a component of nephron we'll mention in a moment. And the vein is drawing back through the renal vein. So the kidney is divided into the medulla and the cortex. In the cortex on the right-hand side diagram, you can see the structure of a cortical nephron, and I will describe its structure in a moment. But really, if you look at the cortical nephron, the glomerulus, and the major components are up high in the cortex. And then you see these straight tubules passing down into the medulla region. I want you to push that last little bit or last loop from the medulla up into the cortex, because really, the very thin loop you see there, the very thin loop of Henle it's called, doesn't really extend down into the medulla from these cortical nephrons. There is also a juxtaglomerular, or should I say juxtamedullary nephron, where the nephron and the glomerulus sit on the border between the cortex and the medulla. And in this case, those straight tubules do descend in the medulla. So, when you see parts of medulla, you can see tubules running in the same parallel direction, and they tend to be of different length. And because of that, when you look at the growth structure of the kidney, you can see pyramids. These pyramids, labelled on the diagram, represent all these tubules, these straight tubules and the collecting ducts running in parallel. And those pyramids are the boundaries of the lobe of the kidney. On either side are the interlobar arteries that I referred to earlier. And then when neuron passes all through the tubules and down through the collecting duct, that collecting duct opens at the base of this, or should I say the apex of this pyramid because the base is actually up against the border of the cortex. The pyramid, by name, is a triangular-shaped region of all these straight tubules and the collecting ducts, as I mentioned before.

    08:00 So you imagine the triangle with the base up against the cortex and the apex is at the tip, the papilla of the pyramid that actually opens into the minor calyx.

    08:14 So urine will drip into that minor calyx and then flow into the major calyxes and then out through the ureter, that you can see on the diagram. So that's a general arrangement of the kidney, mainly its anatomical details, but also some of the microscopic details you'll see in a moment, particularly of the nephron. Let's now look at the kidney in more detail. Here is a section of the kidney on the left-hand side, low power. This is actually a section through the lobe of a kidney. And on the right-hand side is a higher magnification of the cortex of the kidney. I want you to look at this section, or both these sections, very carefully.

    09:03 Look at the cortex and then locate the medulla. This medullary region represents a section through the pyramid that I've described earlier. That pyramid will open at the papilla, the apex of the pyramid, into the minor calyx which is shown there, and then the urine will flow out through the ureter, as I explained before.

    09:26 And you can see components of the heart and there're also a bit of fatty tissue, but you also see a very small artery, a branch of the renal artery. Now, on either side of that pyramid or that medullary region, you have components of the cortex more or less overflowing the lobe. They're called the renal columns. Turn your attention now to the right hand section of the cortex, and you could see little dots or specs.

    09:57 They represent the renal corpuscle. That's the filtering component of the nephron, and I will describe that in more detail in a moment. You can also see some straight tubules that are called medullary rays. There are number of these in this section, several. Have a look at the section and just see if you see regions where they appears to be parallel tubules arranged next to each other.

    10:26 They represent the straight tubules in the cortex and collecting tubules as well, and some of the collecting ducts. And they actually define the central component of the kidney lobule. And if you look in the middle towards the middle part of that section, and also a little bit towards the top, you can see the renal corpuscles are arranged in a sort of a line. And that's because the peripheral border of the kidney lobule is in fact the interlobular artery. They run up on the periphery of the lobule and they give rise to blood to supply the glomerulus inside those renal corpuscles, and then the glomeruli then filter that blood from a filtrate which goes through all the tubule systems, and then follows the collecting ducts in those medullary rays. So again, the medullary rays are the centre of the lobule, and the interlobular arteries are on the periphery. It's hard to see here, I know, because there aren't connective tissue components that separate the lobules apart, as you see in other organs.

    11:48 Now, turn your attention to the left-hand diagram, and we're going to describe the structure of a nephron. Concentrate on, perhaps, the juxtamedullary nephron shown there, because it's drawn a little bit larger and a bit easier then to understand. On the right-hand side, you can see circular structures with a little white hilar around them. They are the glomerulus in the renal, in the Bowman's capsule, that's part of the corpuscle, the renal corpuscle I'll describe in a moment.

    12:27 And all the other profiles you see are going to be profiles through the tubule system. Go back to the diagram. Have a look at the juxtamedullary nephron, and let's just see if we can remember its components. In the center, there's a little round red structure. That's the glomerulus. It sits in Bowman's capsule, which is also a component of that little round red structure. And then you have this tubular system leaving the renal corpuscle and forming rather a cold blue colored structure there. It's a coiled tube. It's proximal to the renal corpuscle.

    13:18 So it's called the proximal convoluted tubule, because it's all coiled. And then you see a straight segment going down towards the papilla of the medulla.

    13:34 That's called the descending straight segment. Then there's a little loop.

    13:39 It's a thin loop. It's a thin segment. That's called the thin loop of Henle. And then it descends as an ascending thin limb of the loop of Henle, and then joins to a thicker red colored part of the tubule system. That's the distal straight tubule as opposed to the proximal straight tubule you saw earlier. And then that ascending distal straight tubule gives rise to another coiled tubule. That's called the distal convoluted tubule. And then that opens into a collecting tubule, and a series of collecting tubules open into the collecting duct, which carries the urine then down and it then drips from the papilla of the renal pyramid.

    14:38 So make sure you understand then the tubule system of the nephron. Proximal convoluted tubule, descending thick limb, then thin segment, descending thin segment loop of Henle, ascending thin limb of Henle, and then the ascending thick limb or segment of the distal tubule and then the distal convoluted tubule emptying into the collecting tubule and then the collecting duct. They are the components of the nephron that function. They do all the important parts of the kidney does that you'll get explained to you in your physiology lectures. Let's now have a look at some of the histological details of those components. So if you can imagine a line or a section taken through that top part where the renal corpuscle is of the nephron you've been looking at, you'll see the sort of image you'll see on the right hand side.

    15:46 Again, sections through the renal corpuscle and profiles through all those convoluted tubules, the straight tubules you'll see down towards the lower region and in the medulla.

    15:58 Here is a diagram explaining the structure of the renal corpuscle.

    16:05 Focus on the yellow colored part of the renal corpuscle. That really is Bowman's capsule. It's a capsule wrapping around another structure I'll describe in a minute.

    16:17 That Bowman's capsule has got a very thin squamous parietal epithelium. And it then becomes continuous on the left hand side with the beginnings of the tubule system, the proximal convoluted tubule. Bowman's space confined within that capsule is where the filtrate is going to go after filtration from the blood capillaries. Now focus on the right-hand side of the diagram and locate an efferent arteriole and an afferent arteriole. The afferent arteriole brings blood in and forms a tuft of capillaries, a very coiled series of capillaries called the glomerulus. And blood flows through that glomerulus and then out through the efferent exiting arteriole. But during development, those vessels embedded. They're pushed up against Bowman's capsule and became encapsulated by the Bowman's membrane, the Bowman's epithelium. So we now call that covering shown here in yellow as the visceral layer of Bowman's capsule. It's like having a balloon and you're sticking your fingers into the balloon. The outer part of the balloon is the parietal layer of Bowman's capsule. And the part of the balloon that's now around your fingers is the visceral layer. Now as you see, that visceral layer is very specialized. The cells aren't squamous. The cells are called podocytes and they are very important part of the filtration process. They're structurally very important for filtration, and I'll show you details of that in a moment. Before we leave this diagram, look across now to the right-hand side and you'll see a tubule, a distal tubule. If you recall from our diagram when the distal ascending tubule or segment travels up, it becomes convoluted. And it becomes convoluted next to the glomerulus.

    18:43 And that's very important because that distal tubule, that convoluted part of the distal tubule is in very close approximation to the afferent arteriole, and also the efferent arteriole. And that forms a complex that I'll describe towards the end of the lecture. It's called the juxtaglomerular apparatus. So just remember that area on the diagram that I've just shown you for later on when I start describing the details. On the left-hand side is I repeated that diagram just to help you recall structures. On the right-hand side is a structure of the glomerulus. You can see Bowman's space and you can see very flat squamous cells lining the parietal layer of Bowman's space, and you can see podocytes that are on the external surface of the blood capillaries in the glomerulus. These podocytes are the visceral layer of Bowman's capsule.

    19:54 You can see red blood cells inside the capillaries. You can see other nuclei besides the podocytes which tend to be on the outside.

    20:03 Those other nuclei probably belong, or certainly, belong to endothelial cells, but also mesangial cells. Embedded in that glomerulus are cells called mesangial cells which support the structure of the glomerulus, support the close association of the endothelial cells of the capillaries with the podocytes. But those mesangial cells are also phagocytic, and they also tend to regulate the flow of the blood through these capillaries. Here now is a diagram explaining the filtration apparatus in the glomerulus. Down the bottom is a diagram illustrating a vessel, a fenestrated capillary that's shown here in orange.

    20:57 The kidney has fenestrated endothelium in the glomerulus to enhance the chance of filtration, to enhance the ability for the plasma to leak out into Bowman's capsule. And when it leaks out, it passes through gaps between the podocyte and a molecular sieve I'll describe in a moment. Have a look at the podocyte.

    21:23 It's colored yellow in the bottom diagram. The podocyte is like an octopus wrapping its tentacles all around the capillary. And as you see here when it wraps its processes around the capillary, it creates filtration slits. And then between the podocyte and the endothelium is the basal lamina. It's a combined basal lamina produced by both the podocyte and the endothelial cells.

    21:54 That's a very important structure too. And you can see details of that in a higher magnification or a higher representation on the top part of the diagram in the little square, or probably rectangle. Now here's an electron micrograph showing the details of that filtration barrier. Let's orientate ourselves. Down the bottom is the lumen of the capillary in the glomerulus. It has got fenestrations or little gaps in the wall. So the plasma is going to move out through those fenestrations. And then it confronts this basal lamina, which I said was produced by both the podocyte and the endothelial cell. It's a fairly thick layer. It's a molecular sieve.

    22:53 It prevents certain substances, molecules, from passing through it.

    22:57 Most proteins, for instance, are too large to get through that sieve. It's anionic so it tends to repel negatively charged molecules. And then further filtration is achieved by substances passing through this molecular sieve then through the filtration slits created by those podocyte processes, and there's also a very very thin molecular diaphragm there. It also participates in the filtration process. Finally, the filtrate passes into the luminal space or Bowman's space.

    23:40 And that's the urinary space. And up on the top, you can see part of the cell body of one of these podocytes. So that's the filtration apparatus, and filtration is achieved by the hydrostatic pressure created by the efferent arteriole having a smaller diameter than the larger afferent arteriole. And this pressure here created across the glomerulus achieves the pressure required to drive that plasma filtrate through the molecular sieve into Bowman's space.

    24:16 Let's have a look at some details now of the tubule system, diagrams to remind you of the tubules, the types of tubules.

    24:25 And on the right, you can see a glomerulus sitting in Bowman's space, Bowman's capsule. And you can just see the beginnings of the urinary pole, the beginnings of the proximal convoluted tubule. There's the urinary pole labelled and proximal convoluted tubules. You know the glomerulus or at least the kidney overall filters about 180 liters perhaps, of blood a day. And of that 180 liters of blood, or should I say 180 liters of filtrate that passes through these glomeruli into Bowman's space, about 140 is reabsorbed in the proximal convoluted tubules. The proximal convoluted tubules are responsible for absorbing back into the blood 65% to 70% of everything that was passed out in the filtrate. So they're extremely busy cells. And for that reason, they stain very eosinophilic in this section, in normal H&E sections, because they've got large factories, mitochondria, to provide energy for all the active transport processes for absorbing all that material back into the system. They also have various basal foldings and mitochondria there to again have channels and transport mechanisms to take material back from the lumen of the proximal convoluted tubule that's been filtered back into the blood, back into the body. So they're extremely active cells.

    26:12 And they have a microvillus, brush border, which you don't appreciate here because it's very often hard to see them and to even preserve the tissue well enough to see them, particularly in H&E sections. But you see a rather undulating luminal border, representing microvilli, and also the very large cells of these proximal convoluted tubules. They are very, very busy cells. And they're easy to distinguish from the distal convoluted tubules, which are rather pale staining, more cuboidal, and they are doing less of the workload I guess. They are doing very important functions that the physiology lecturers will explain to you. But at least here, now you should be able to distinguish, the glomerulus, Bowman's space, and now, the proximal convoluted and distal convoluted tubules. Up in the cortical region, you'll also have collecting tubules. These are very small stained lightly structures you see, very thin. And if you look very very carefully along the epithelial cells, you often see a hint of the little lines between the cells representing where the lateral borders of these cells are joined together to stop material leaking back into the blood from the urinal space or the space within the collecting tubule. They're often hard to see. But certainly, at least in this section, you can make out the very eosinophilic stained proximal convoluted tubules in this region. Here, a section through the straight tubules.

    28:09 You're looking now down, perhaps, in the medullary region, or at some part of the medullary rays in the cortex. Again, you can make out proximal straight tubules from distal straight tubules, because of the staining characteristics between the two that I've described before because of the high activity of these proximal tubules. And on the right-hand section, you can see profiles of the thin segments, the descending thin limb, the ascending thin limb, and even the loop region. They're also often hard to see because they are very very thin, as their name suggests, and they're lined by just a simple squamous epithelium. And they're seen best here when they're cut transversely.

    28:58 When we want to identify collecting ducts, it's quite an easy exercise, particularly if we're looking in the papillary area or the pyramid area of the medulla. You can identify them because again, like the collecting tubule, these cells have very fine lateral borders that you can just see in sections, in H&E sections.

    29:26 Have a look carefully along the epithelium lining this collecting duct, and you can certainly see the nice round nuclei, but you can also see little fine pink lines that represent the junction or borders between these cells. Again, it's to stop contents leaking back into the system, into the vascular system, and then back into the body, because these tubules now contain the urine that's now destined to be passed down through the ureter to the bladder and then eliminated. And then finally, when the urine passes down through the collecting ducts to the papilla of the pyramid, the apex of the pyramid that then passes into the minor calyx and then down the ureter towards the bladder for storage.

    30:22 Note the epithelium on the minor calyx. It becomes rather stratified.

    30:30 We're going to call that transitional epithelium. We're going to refer it also to urothelium. And just finally, well, as we're talking about the nephron, sometimes the term uriniferous tubule is named. That refers to the nephron and the collecting duct to which that nephron passes urine too. Let me now explain the vascular supply to the nephron. I've already explained that blood enters the glomerulus from the afferent arteriole arriving. It then breaks into the capillary bed, the glomerulus that I've described, where the podocyte wrap around. And then the blood leaves via the efferent arteriole, the exiting arteriole. That blood then forms a capillary network, another capillary network.

    31:32 And in the cortex, in the cortical nephrons, this capillary network is called the peritubular network. It wraps around all the tubules and then drains into corresponding veins and then out of the kidney. And remember, they're the important capillaries that send oxygen levels and then can secrete erythropoietin. In contrast, the efferent arteriole in the juxtamedullary nephrons, they do a different thing. They form a network that then follows parallelly all the straight tubules going down into the medulla, in the pyramids. And this is a very important relationship. Running parallel to these tubules, these capillaries called the vasa recta are able to participate in a countercurrent mechanism that concentrates our urine. And again, the physiologist will explain about the role that these vasa recta have in doing that.

    32:43 On the right-hand side, you can see a section through the medullary portion of the kidney, the pyramids. And you can see the vasa recta stained here, the red blood cells. They form an enormous network around these straight tubules.

    33:03 And then finally, that blood passes out again through the venous system into the renal vein.

    33:09 I want to now go back to what I was talking about earlier when I mentioned the macula densa cells and the juxtaglomerular apparatus. On the left-hand side of the diagram, the macula densa cells are a group of cells right up close to the efferent arteriole. They're part of the distal convoluted tubule, and they're shown in yellow at the top of the diagram.

    33:39 They're called macula densa cells because they're concentrated together, the nuclei look very close together.

    33:47 Dense spot is what macula densa means. And they're actually in very intimate contact with mesangial cells outside the glomerulus called the extraglomerular mesangial cells, but also they're in direct contact with cells or smooth muscle cells of the efferent arteriole. And those smooth muscle cells get a special name.

    34:12 They're called juxtaglomerular cells. And there are gap junctions joining all these cell components together. And the distal tubule detects sodium chloride concentration and blood pressure. When sodium chloride concentration is very low in the distal convoluted tubule or if blood pressure is low, those macula densa cells stimulate the juxtaglomerular cells to secrete renin.

    34:46 And renin, therefore being a hormone, passes into the vascular system and initiates what we term the renin-angiotensin-aldosterone complex or system that again, you'll learn in your physiology. So this is a very important component of the kidney, controlling blood pressure and also some degree oxygen levels and content of the blood itself. It's a monitoring unit.

    35:24 These juxtaglomerular cells are often difficult to see because often, you don't see sections where you see both the relationship of the distal convoluted tubule to the efferent arteriole. Let's briefly now look at the ureter, shown here on the right hand side. It's a muscular tube. It passes the urine down to the bladder. It's lined by what we call a transitional epithelium or a urothelium.

    35:57 And this persist this type of epithelium all the way down through the bladder, and to some degree, through the urethra. It's called transitional epithelium because it changes its appearance. When the bladder and the ureter is distended during flow of the urine, the epithelium changes its shape. And because of that, it's called transitional, and I'll describe that in a moment. But it's just a muscular tube. Here is a section of the bladder on the right-hand side. Have a look at the diagram of the male bladder indicated here. It's a bag for storing urine.

    36:38 And on the right-hand side, you see sections through the mucosa of the bladder when the bladder is empty, and the mucosa and the epithelial cells, in particular, are very thick. It's a very thick stratified layer. On the left-hand side is this epithelium of the bladder, and it's typical of the epithelium of the ureter as well, stratified epithelium. Notice on the surface of these cells, there are some eosinophilic stains. These are plaques.

    37:12 And what you see here on the right-hand side is the bladder when it's distended, and the surface cells flattened out from the more cuboidal shape that you see at the surface on the left-hand side in more a relaxed bladder. Hence the name transitional epithelium, but also gets the name urothelium. Those plaques are very, very important, because what they do is they prevent water and salts going back, out of the bladder back into the body. They form a seal and they're impermeable, which is very important when you're storing rather toxic substances and components of the blood you feel that you don't want in the body. You want to eliminate in the urine. And finally, the male and female urethra. In the female, it's short. The urothelium persists for a while and then it changes to a non-keratinized stratified squamous epithelium. In the male, the urethra is long because there are three different parts, the prostatic urethra, the membranous urethra, and the penile urethra. There's a little star next to the urethra, the membranous urethra in the male because that's where urothelium changes from typical transitional epithelium I've described to stratified squamous epithelium throughout the penis and then beyond towards the skin. Sometimes in the urethras you find mucus secreting glands, which are probably there just to protect the epithelium from perhaps an acidic urine.

    39:00 So let's just summarize now what the functions of these components are.

    39:07 The kidney has a very important structure of the nephron, which consists of the glomerulus filtration apparatus. And all the tubules that you will learn in physiology have a very important role in filtering our blood, getting a filtrate plasma based solution, and it then gets rid of products that we don't want to retain, or excessive products, and passes it into the urine. The ureter conveys that urine to the bladder, the bladder stores that urine and make sure things don't leak back into the system, into the body. And the urethra is the tube whereby we eliminate urine from the bladder in both the male and the female. So I hope you now understand histology of the major organs of the urinary system. And thank you very much for listening to this lecture.

    About the Lecture

    The lecture Urinary System by Geoffrey Meyer, PhD is from the course Urinary Histology. It contains the following chapters:

    • Urinary System
    • General structure of the kidney
    • Nephron
    • Renal corpuscle
    • Filtration apparatus
    • Tubes of the nephron
    • Juxtaglomerular apparatus
    • Urothelium and urethra

    Included Quiz Questions

    1. Production of vitamin E
    2. Retrieval of water and amino acids
    3. Acid-base balance of body fluids
    4. Regulation of blood pressure
    5. Retrieval of salts and proteins
    1. renal artery, interlobar artery, arcuate artery, interlobular artery
    2. interlobar artery, renal artery, arcuate artery, interlobular artery
    3. arcuate artery, renal artery, interlobar artery, interlobular artery
    4. interlobular artery, renal artery, interlobar artery, arcuate artery
    5. renal artery, arcuate artery, interlobular artery, interlobar artery
    1. Forms the boundaries of the lobes of the kidney
    2. Consists of straight tubules and collecting ducts running in parallel
    3. An interlobular artery is located on either side of the medullary ray
    4. The base of the pyramid lies against the boundary of the medulla and cortex
    5. The apex of the pyramid opens into the renal papilla then minor calyx
    1. Is a component of a renal column
    2. Consists of straight tubules and collecting tubules in the cortex
    3. Defines the centre of each kidney lobule
    4. May contain some collecting ducts in the cortex
    5. Have a interlobular artery at its periphery
    1. proximal convoluted tubule, descending thick limb/segment of the proximal tubule, descending thin limb, loop of Henle, ascending thin limb, ascending thick limb/segment of the distal tubule, distal convoluted tubule, collecting tubule, collecting duct
    2. proximal convoluted tubule, descending thick limb/segment of the proximal tubule, descending thin limb, loop of Henle, ascending thin limb, ascending thick limb/segment of the distal tubule, distal convoluted tubule, collecting duct, collecting tubule
    3. distal convoluted tubule, descending thick limb/segment of the distal tubule, descending thin limb, loop of Henle, ascending thin limb, ascending thick limb/segment of the proximal tubule, proximal convoluted tubule, collecting tubule, collecting duct
    4. proximal convoluted tubule, descending thin limb/segment of the proximal tubule, descending thick limb, loop of Henle, ascending thick limb, ascending thin limb/segment of the distal tubule, distal convoluted tubule, collecting tubule, collecting duct
    5. proximal convoluted tubule, descending thick limb/segment of the proximal tubule, descending thin limb, ascending thin limb, loop of Henle, ascending thick limb/segment of the distal tubule, distal convoluted tubule, collecting tubule, collecting duct
    1. ...form the visceral layer of Bowman's capsule.
    2. ...are squamous epithelial cells.
    3. ...lie adjacent to the distal convoluted tubule.
    4. ...lie adjacent to the afferent arteriole.
    5. ...lie adjacent to the efferent arteriole.
    1. fenestration, basal laminae of both the endothelial cell and the podocyte, filtration slit of the podocyte, filtration diaphragm of the podocyte, Bowman's space
    2. fenestrations, basal lamina of the endothelial cell, filtration slit of the podocyte, basal lamina of the podocyte, filtration diaphragm of the podocyte, Bowman's space
    3. basal lamina of the endothelial cell, fenestration, filtration slit of the podocyte, basal lamina of the podocyte, filtration diaphragm of the podocyte, Bowman's space
    4. filtration slit of the podocyte, fenestrations, basal laminae of both the podocyte and endothelial cell, fenestration, filtration diaphragm of the podocyte, Bowman's space
    5. fenestrations, basal laminae of both the podocyte and endothelial cell, filtration diaphragm of the podocyte, filtration slit of the podocytes, Bowman's space
    1. Macula densa cells respond to low concentration of sodium chloride in the lumen of distal convoluted tubules and stimulate juxtaglomerular cells in the afferent arteriole to secrete renin
    2. Macula densa cells respond to low concentration of sodium chloride in the lumen of proximal convoluted tubules and stimulate juxtaglomerular cells in the afferent arteriole to secrete renin
    3. Macula densa cells respond to high concentration of sodium chloride in the lumen of distal convoluted tubules and stimulate juxtaglomerular cells in the afferent arteriole to secrete renin
    4. Macula densa cells respond to low concentration of sodium chloride in the blood of the afferent arteriole and stimulate juxtaglomerular cells in the afferent arteriole to secrete renin
    5. Macula densa cells respond to low concentration of sodium chloride in the lumen of distal convoluted tubules and stimulate mesangial cells in the glomerulus to secrete renin

    Author of lecture Urinary System

     Geoffrey Meyer, PhD

    Geoffrey Meyer, PhD

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    By Niamh D. on 03. May 2017 for Urinary System

    The content of this lecture is very detailed and well explained.

    Great teaching professor Geoffrey Meyer, Thank you
    By Hossam W. on 13. January 2017 for Urinary System

    One of the best lecturer i have seen, keep up the good work!