Alright Ninjanerds, we're going to talk about the kidney today. So if you look here, we have the kidney, the kidney bean shaped and we have two of them, right, so you'd have them - in the abdominal actual area, so the abdominal cavity So if you look here you're going to see this nice little connective tissue That's actually surrounding the kidney- there's actualy three layers but we're gonna talk about this one first. It's actually called the renal capsule It's made up of a alittle bit like loose connective tissue and basically it's job is to prevent certain types of infectious micro organisms from spreading into the kidney Now just for your information, there is other connective tissue surrounding it like outside of this one, so more superficial to this one which is called the perirenal fat capsule and that's a adipose tissue that's surrounds it and also is helpful for being able to cushion the actual kidneys and there's also one more, actually called the renal fascia which is like a dense fiberous irregular connective tissue that anchors it to the actual surrounding structures to keep it retroperitoneal, which means behind the peritoneum Alright If you look here, at the kidney, You can't see it, but imagine it There's like a slit-like space So a little hole here, where example the renal arteries going in, the renal vein is coming out, and the ureter is coming out There's a little slit-like space where all of these structures are going in and out Tha'ts called the renal hilus, okay That's very different from what's called the renal sinus The renal sinus is in this area, it's basically like a plumbing of the kidney. It's like this area or this space, which consist of the renal pelvis the renal artery, the renal veins, and other different structures in this area, okay? Now that we've done that, let's look at different parts of the kidney here So if you look here, this is actually going to be this outer granulated tissue out here, all of this kind of beige colour here, all this part here too All the way around is actually called the cortex, so it's called the renal cortex, okay? Deep in the actual part of the kidney is this nice little dark striated types of tissue. That is actually called the renal medulla - and if you kind of look at the renal medulla it kinda appears to look like a pyramid, right? So that's like a renal pyramid, a renal pyramid a renal pyramid and a renal pyramid and they just keep going down. So again renal medulla is this dark striated colour and then they look like pyramids so you call these renal pyramids, okay? Next thing, you notice number 23 right here? It's like an inward extension of the cortical tissue So if you notice, here's the cortex and then there's the little extension and it dips down into the medulla These are called the renal columns, okay? So thats called the renal column. So the renal columns are inwards extensions of the cortex alright? So there's another example of a renal column, a renal column, and over here there's also a renal column. Alright! Next thing. If you look at the end here, the end of this renal pyramid that we said, this is the renal pyramid part of the renal medulla at the end of the renal medulla all the way at the bottom the end part right there number 6, is called the renal papilla Okay, so that's called the renal papilla. The renal papilla- empties the actual urine, into this little like tube here you see, this little tube right there guys? That's called the minor calyx So every renal papilla empties their urine off into for an example this is a minor calyx minor calyx, minor calyx, minor calyx right there but what happens is, when multiple minor calyces actually come together, they form a major calyx So look right here, minor calyx, minor calyx These guys will actually join together, there's a minor calyx and a minor calyx, they'll come together and form this big structure here which is called the major calyx Okay? The major calyces will actually join and actually form this big, big structure which is called the renal pelvis, number 4. So it's the big, big joined structure of multiple major calyces and again that forms the actual renal pelvis and then once the renal pelvis exits the kidney and goes out of the hilus, it becomes this big structure here number 3, which is called the ureter, okay? So again one more time, minor calyx and then all of this once you have minor calyces joined together they form a major, and then again over here minor will join together to form a major and all of those major calyces empties into whats called the renal pelvis and the renal pelvis exits the actual ureter- i'm sorry exits the kidney as the ureter Alright! Another thing. We need to talk about the arteries, the blood flow to the actual kidney. So let's go ahead and follow a drop of blood from what's called the abdominal aorta and into the kidney. So coming- like imagine theres the abdominal aorta here. Off the abdominal aorta you have an artery - number 2. That number 2 is called the renal artery (lat: a. renalis). Okay, so it's the renal artery. The renal artery, once it enters into the kidney through the hilus it splits into 2a. 2A is called the segmentary artery So again, 2 is renal, 2A is segmental Then the segmental artery goes into what's called the interlobar artery Number 13 Now, if I tell you what a lobe is, it's gonna help you understand what number 13 is. So a lobe of the kidney because you have multiple lobes in the kidney - let's say I call a renal lobe, I am actually gonna cut around this renal pyramid all the way so from this part of the renal pyramid all the way up, and the surrounding cortex, so all the way up here, all the way over here and down this way, right there So all this I kind of chuncked out that's all a lobe of the kidney, so to define a lobe as the renal pyramid and the surrounding cortical tissue. This artery here is called the interlobar artery So if this is a lobe of the kidney, and this is a lobe of the kidney The interlobar artery runs inbetween those two. Its the interlobar artery The interlobar artery is actually gonna move up through the actual lobes and as it gets to the top part of the cortex, it starts branching off So you see number 16 here? and you'd also see again heres an interlobar artery coming up this way and branching this way This branch and this branch is called the arcuate artery - so number 16 is the arcuate artery Then the arcuate artery as it's moving up it gives off these branches, you see these little branches coming off here? All this one, this one, this one, this one, this one that red one there, these ones that are actually getting radiated up into the cortex is called the cortical radiated artery. So this is the cortical radiated artery, cortical radiated artery, cortical radiated artery cortical radiated artery. Then, that cortical radiated artery has whats called an afferent arteriole. It's not very well seen on this model, so i'm going to show this on you another model in just a second But just for right now, trust me that the cortical radiated artery feeds into whats called an afferent arteriole, then into the glomerulus and then through the efferent arteriole and then it comes out of the efferent arteriole and then it goes to what's called a peritubular capillaries. From the peritubular capillaries, it comes down through whats called the cortical radiated veins You see this vein right there guys? Right next to the cortical artery, thats called the cortical radiated vein The cortical radiated vein then actually moves back down so look, it actually comes here And as it moves, it joins with the arcuate vein So you have cortical radiated vein, arcuate vein and then look what happens - i'll show you this way too cortical radiated vein joins with the arcuate vein, and empties into whats called the interlobar vein Okay, so thats the interlobar vein there Then the interlobar vein joins with other interlobar veins and form whats called the renal vein you see the number 1, right there? That's called the renal vein. So again, one more time - the cortical radiated vein join the arcuate vein forms what called the specifically interlobar vein The interlobar vein will then actually join with other interlobar veins and form whats called the renal vein. If you've noticed, there's no segmental veins here, alright. In the other enlarged, we're gonna look at an enlarged lobe with a nephron, we'll be able to see other structues, that'll really really help us understand the actual kidney anatomy. So lets go ahead and move on and look at the actual enlarged lobe and the nephron. Alright guys, so now we're taking a look at the- like an enlarged view of a kidney lobe - right, so lobe of the kidney. And again what was a lobe defined as? It's defined as the renal pyramid Right? and it's surrounding cortical tissue. So this is a lobe here. Now, let's keep going and show you what I couldn't show you before when we got into some of the smaller arteries here. So if you remember this artery right here kind of follows up here it's actually moving in between the lobes, remember that one? It's called the interlobar artery, so this is the interlobar artery right here number 12 So the interlobar artery is moving up and then as it moves up, it gives off that branch, right, around the actual cortex, it gives off this branch right here So this branch right here, and you'd see it over here right there, all the way over, so number 7 if you will, so following up is interlobar then it gives off a branch which is called the arcuate artery Okay? Now, what happens is, the arcuate artery is gonna start feed up here So if we feed it up here, you see as it comes up here number 8, as we follow this all the way up it's like a branch going straight into the cortex here this one right here is called the cortical radiated artery, just like this one over here is also called the cortical radiated artery So now cortical radiated artery here, cortical radiated artery here they give off branches, so you see these tiny little branches right there? We'll even see these even better when we look at what's called a renal corpuscle but if you see this tiny little guy right there that is called the afferent arteriole. That little branch right there. That also is an afferent arteriole and that one right there is an afferent arteriole, just like this one is also and that one - so 9 is the afferent arteriole. What happens is the afferent arteriole feeds into this little structure right here, so you see this little structure here? This little like beige tan looking ball? This is actually called a renal corpusculum And what are renal corpusculum made up of? and we'll see this in a better view, it it's made up of a tuft of capillaries which is called the glomerulus and the surrounding Bowmann capsule, but we'll talk about that. For right now, just know that the afferent arteriole feeds into this thing called a renal corpusculum. and then what happens is it gets drained by another arteriole, you see this one right there? That's called the efferent arteriole, this one would also be an efferent arteriole. This one over here would be an efferent arteriole. So it's going in to here, getting filtered through the glomerulus and coming out of what's called the efferent arteriole, number 10 also efferent arteriole, and also efferent arteriole. Okay? So interlobar, arcuate, cortical radiated, afferent, glomerulus, efferent. Now the efferent arteriole as they're coming out they start branching into smaller little capillary networks You see this whole capillary network right here? This whole capillary network is called the peritubular capillaries. Okay? So all this capillary network that the efferent arteriole branch into, is called the peritubular capillaries The peritubular capillaries are important for secretion absorption, we'll talk about that in physiology but as we drain the peritubular capillaries, they all drain into this main vein, you see this number 8 here? That main vain That right there is called the cortical radiated vein so it bringing the actual blood, deoxygenated blood, all the way down from the cortex going towards the medulla Okay? So now this cortical radiated vein is coming down, right? It's gonna join with this blue vein right there. What's this one? It's called the arcuate vein. Remember I told you that the efferent arteriole gave off the peritubular capillary branches? Well there's another peritubular capillary branch that it actually feeds into. This is the efferent arteriole. This is also an efferent arteriole. You see how it actually gives off this branch? This big, big capillary network here? This big, big capillary network - it's a peritubular capillary but it's in the medulla, so we give it another special name. So this big big peritubular capillary network here is called vasa recta. Okay? So again, efferent arteriole, gives off a branch that feeds deep down into the medulla and forms this capillary network, and this capillary network is called the vasa recta. It's very important for being able to concentrate urine, and we'll talk about that. So again, efferent arteriole, vasa recta the vasa recta has blood that can also drain into arcuate vein So arcuate vein, blood from the vasa recta and the cortical radiated vein all dump their blood into this main moving down inbetween the lobes, so this main vein coming all the way down here is going to be number 12 is going to be the interlobar vein. Okay? and if you remember the interlobar vein will actually feed into the renal vein and then go back to the inferior vena cava. Alright now! Let's come back to the glomerulus So if we go back to the glomerulus, the little capillary network inside the renal- it's a part of the renal corpusculum, inside the Bowmans capsule If you look here, 20, it's a little capillary network. That's called the glomerulus. What the glomerulus does is, it filters certain types of plasma components out of the blood and into the little like tubes here. Alright? So you see this little membrane here that's kinda surrounding it all the way around? That's called the Bowmans capsule Okay? What happens is once the fluid that plasmas filtered to, it drains into this Bowmans capsule and then it goes into this like coiled tube. You see this little coiled tube like this? That's called proximal convoluted tubule. Okay? So this little thing right here surrounding glomerulus is the Bowman capsule but then this tube that's coiled is called the proximal convoluted tubule Then the proximal convoluted tubule goes down to what's called the descending limp of the loop of Henle, and then through a little thing section of the descending limb. Then it goes down and it comes back up to the ascending limb of the loop of Henle. So descending limb, thin section, ascending limb of the loop of Henle. Then as it comes up back into the cortex, look, it starts getting coiled and like convoluted again right? So it comes up, ascending limb? Look. Bom, get's coiled again. This little coiled part here is called the distale convoluted tubule. Okay, so one more time. Bowman's capsule, proximal convoluted tubule, descending limb, thin section, ascending limb, distale convoluted tubule. The distale convoluted tubule dumps its actual filtrat into this big long structure, all the way down here you see this guy right there? All the way here This is called the collecting duct So number 6 is the collecting duct. Now, one more term I wanna give you guys is you know how I said the Bowmans capsule, proximale convoluted tubule loop of Henle and distal convoluted tubule That makes up what's called the nephron, okay? So a renal corpusculum is the glomerulus and the actual Bowmans capsule but a nephron is the Bowmans capsule, proximal convoluted tubule, loop of Henle and again the distal convoluted tubule. Alright? And again this is the collecting duct Now as the filtrate actually moving down the collecting duct, it'll get to the end of this actual renal pyramid here, what was that little [..] of the renal pyramid called down here? This is called the renal papilla, right. Well, there's a little duct portion here at the renal papilla, that's called the papillary duct And once this is actually at the papillary duct, it's now urine and it drops off of the papillary duct of the renal papilla, and into that minor calyx. Okay? Alright so that covers everything we need to see here on the enlarged lobe of the nephron.Now lets go ahead and zoom in on this actual renal corpusculum and take a deeper look at that. Alright, so now we're gonna take a deeper look at the renal corpusculum. So you guys remember, like this is actually that little larger- like a smaller view of that renal corpusculum what we're gonna do is, we're gonna look at that in a way, way deeper view. So this is a renal corpusculum, so again what is the definition of a renal corpusculum? It is the glomerus capillaries and the surrounding, it's called, Bowmans Capsule So now feeding this glomerulus capillaries is this artery here, called the afferent arteriole so the afferent arteriole is the artery thats feeding the glomerulus draining it, is number 7 over here, this is the efferent arteriole. Okay, so afferent arteriole efferent arteriole. Afferent feeds the glomerulus capillaries and efferent drains the glomerulus capillaries Okay another thing, if you look here at the actual afferent arteriole, there's this like, you see these little structures here? It's like zooming in to the inner side of it In the afferent arteriole you have whats called these cells called JG-cells, or juxtaglomerularcells. These juxtaglomerularcells are like basically pressure-receptors. They are baro-receptors and mechano-receptors and they can have the ability to sense changes in blood pressure and stretch. When that happens, they have vesicules that they can secrete specific types of chemicals, like renin and renin helps to regulate our blood pressure Okay so afferent arteriole and then theres what's called the juxtaglomerularcells in it. Now since i'm here, you see these actual things in the back here? This is actually called, this is a portion of the distal convoluted tubule. In the distale convoluted tubule, you have these specific cells, that are like chemo-receptors so they pick up different chemical concentrations These cells right here are called the macula densa cells and again, they're actually located in the distal convoluted tubule and they're basically special chemo-receptors. So, what happens is we actually define this whole apparatus, we actually have like an apparatus, let's say I make a whole circle here around the distal convoluted tubule with the macula densa cells, around this afferent arteriole with the JG-cells This whole thing, if I kind of make a whole circle around this this is called the juxtaglomerular- apparatus and it consists of the JG-cells in the afferent arteriole, and the macula densa cells in the distal convolute tubule, okay. Now let's take a look at the glomerulus. So the glomerulus is this tuft of capillaries But if you notice, and it's actually fenestrated capillaries if you notice, this is actually the raw capillaries here but if you notice theres this like beige tan covering on it They're actually having cells clinging to the capillaries and this actually forms whats called the visceral layer of Bowmans capsule, and this visceral layer of Bowmans capsule is these simple squamous cells, modified simple squamous cells they're actually called podocyts, which means foot cells So there's these little podocyts that are litterally clinging on to these glomerulus capillaries, and these are forming the visceral layer of the Bowmans capsule and then this inner layer, this outer layer here, sorry, this outer layer out here, I kind of follow it over here too and just this whole out thing here it's actually made up of simple squamous epithelial cells too, but this whole outer layer here that's even continous with this actual podocyts visceral layer. This layer here is called the parietal layer of Bowmans capsule, so one more time The podocytes make up the visceral layer of the Bowman capsule and this outer part is the parietal layer of the Bowman capsule Alright, last thing we're gonna finish this off is if you see this Bowmans capsule is actually getting getting drained by this next structure, and it's just the small pierce of it, you see this, it's like little like simple cuboidal epithelial cells This is actually called the proximale convoluted tubule. It processes a lot of different types of nutrients and solutes and small proteins and we'll talk about that in renal physiology Okay? So this whole thing is the proximal convoluted tubule Alright so lets get a quick recap, guys so this is the afferent arteriole this is consisting of the JG-cells, which again is releasing renin that controls blood pressure, so they're baroreceptors, right then again, you have the efferent arteriole, then you have the macula densa cells, which are a part of the distal convoluted tubule they're like chemo-receptors and then this whole area of the macula densa cells and the JG-cells is the juxtaglomerular apparatus These cells are clining to the actual glomerulus capillaries, and is called podocyts they form the visceral layer of Bowmans capsule The actual glomerulus capillaries are fenestrated capillaries very porous and then this outer layer here is called the parietal layer of the Bowman Capsule, okay, and it's also very continous with the visceral layer and then we have the proximal convoluted tubule down here, which is gonna be very important for absorbing specific types of nutrients, and for secretion of like, certains types of chemicals. Alright Ninjanerds, I hope all of this made sense, I hope it helps, until next time.
