iron engineers in this video we're going to talk about the loop of Henle now if you guys in haven't already seen it I want you guys to go into the actual of specifically the kidney playlist and take a look and watch the government filtration and the proximal convoluted tubule video before you guys come in watching a little of handly videos so that you guys can tie it all together okay so loop of Henle and there's two parts to the loop of Henle so looper family consists of the descending limb which is this part here and then coming up the a sending limb so again let's actually define that again so the loop of Henle is broken into two parts one is the descending limb and we're going to talk about this one first and then the second one the other component of the loop of Henle is the a sending limb now before I do this I want to introduce another term that you guys might not have been familiar with or you might be familiar with this term is called nephron so I want to talk about this term called nephron so nephron what is a nephron okay so nephron you remember we talked about this and within the actual glomerular filtration video it's consisting of a renal corpuscle so what's a renal corpuscle consisting of this right here the glomerulus and the associated Bowman's capsule right so so far what's gonna from I made up of let's put in like a little like a maybe like a little a mathematical equation here will say glomerulus plus Bowman's capsule plus we already talked about the proximal convoluted tubules so this is another component the proximal convoluted tubule so put PCT it's also going to be the loop of Henle so the descending and the a-standing limb so we're also going to add loop of Henle to this and then the last part is the distal convoluted tubules and that's this part that we'll talk about in the next video this is what's making up our nephron now our nephron again one more time is made up of the glomerulus which is the capillaries the Bowman's capsule the proximal convoluted tubule the loop of Henle and the distal convoluted tubule you know within one kidney you have about 1.2 million nephrons which you don't usually have two kidneys so if you have two kidneys how many total nephrons does that make then 2.4 million of these nephrons within your two kidneys that's unbelievable okay so now let's get back to the loop of Henle so the loop of Henle is a component of the nephron right so let's talk about the descending limb first so if you guys remember what if we caught catch up we had filtration the common filtration process right after that we had this process of tubular reabsorption of certain types of chemicals right and we had the process in which we discussed tubular secretion of certain chemicals right so again this is called tubular secretion and this right here is called tubular reabsorption now I got to get some numbers in here again sorry guys I really wish I didn't have to do all these numbers but if you remember what was the osmolality with inside of the glomerulus it was approximately 300 milliosmoles what was it when it went into the Bowman's capsule it was approximately 300 milliosmoles here's the next question what is it when it leaves the proximal convoluted tubule some of you might be like blown away by this some of you might understand it it's 300 milliosmoles you're probably like holy crap Zak you reabsorbed a lot of different salts and bicarb and nutrients and all that kind of stuff why would it be a 300 milliosmoles shouldn't it be less no why I'm gonna tell you I out of the substances that you reabsorbed remember that we had 65 percent of that was actually sodium and how much of it was water exactly the same amount 65 percent of it was also water if you reabsorb the same amount of water and sodium ions into the blood don't you have the same amount being reabsorbed so if that same line is being reabsorbed then that what's coming into this actual loop of Henle the descending should now be the same as the actual plasma osmolality so it's 300 milliosmoles so it's also it's what we refer to as isotonic with the blood plasma so this is isotonic with the blood plasma and then the actual filtrate in the actual Bowman's capsule is also isotonic with the blood plasma meaning it's equal but watch what happens here as we're actually coming down this actual specifically about renal medulla because whenever you get to the nephron loop this loop of Henle it's dipping down into the actual renal medulla so as it's dipping down into the renal medulla look what happens to the actual concentration of the actual osmolality as we move down so right here it's about 300 milliosmoles then as you move down it gets to about 500 million holes if I move down even more it gets to about 700 million holes if I move down here it's about 900 million holes and then all the way down here it's about 1200 milliosmoles if you're looking what's happening to the actual the plasma osmolality or just I'm sorry this actual medullary interstitial osmolality what's happening it's getting saltier or more hypertonic as you go down the renal medulla so as I'm moving down this renal medulla the actual concentration of this actual salty ions are actually increasing it's getting becoming more salty as I move down I should not talk about osmolality osmolality okay if you remember we said that if there's a high osmolality that refers to specifically high amounts of sodium and chloride in the blood right there's a lot of solutes in the blood so we can refer to this as solutes and then we said that was a very low amount of water this is referred to as when I have high amounts of salt and low water this is referred to as hypertonic now let's do this another way let's say we do it like this now what if the sodium chloride or the sodium and the chloride and the different types of solutes in the blood let's say that this is less and then the amount of water is more when this is the case this is referred to as hypotonic and what would this person with osmolality be this person's osmolality would be osmolality would be very very low but now let's say the last scenario so let's take the last scenario and let's say that the sodium chloride or just our solutes in general is equal to the amount of water what's that referred to this is referred to as isotonic okay so now we have to take this into consideration now that we understand what these terms of osmolality and hypertonic hypotonic isotonic means let's look at this as we're moving from the actual cortex all the way down deep to the renal medulla down to the renal pyramids all the way down to that pepillo what's happening to the osmolality it's increasing so what does that mean if awesomo ality is increasing that means there's a lot of sodium and a lot of chloride ions in that area and very little water okay how in the heck am I getting this salty I'm glad you asked you see this googly-eye frickin guy light right there you see that googly eye guy that googly eye guy is a very special transporter this googly eye guy is called a sodium potassium to chloride cotransporter holy crap that was a lot right has a mouthful but again that's what this guy is this googly eye guys are going to be sodium potassium 2i2 chloride co-transport look what they transport they take sodium they take potassium and they take chloride ions and they transport it all from the actual lumen of the actual filtrate into this actual tube you'll sell of the a sending limb and then there's special transporters or special types of channels here on the basolateral membrane and each one is specific to these guys so there's B right here let's say that's a sodium channel let's say that this one right here is going to be a potassium channel and let's say that this one right here is actually going to be a chloride channel what happens chloride is going to get pushed out what's gonna happen to the sodium he's going to get pushed out now the potassium some of it a small amount of it will actually leak out but some of it will actually stay in this area we'll discuss that in just a second here but now what's getting really really concentrated out in this area then we're having a lot of sodium concentration is increasing so a lot of sodium is going to get pushed out here let's show a lot of sodium ions increasing on this area and that's why it's getting solved here what else is increasing in this area there's also going to be a lot of chloride ions in this area there's gonna be a lot of chloride ions in this area because they're also getting pumped out here too so what is this what did I just say as we're going down it's getting saltier why is it getting saltier because the sodium potassium to Clio transporters are active are actually pumping this not actively they're pumping this sodium this chloride and some of that potassium out here so what is going to be doing here same thing so what will this be pushing out sodium it'll be pumping out potassium some of that potassium will actually stay out here though we'll talk about why in a second and then chloride is also going to be pushed down so what's happening to the concentration of chloride concentration is increasing the sodium concentration is increasing and the potassium concentration is increasing just a tiny bit nothing significant will be like a tiny little arrow there okay but either way nonetheless what's happening to the concentration out here it's getting Alti in saltier and saltier as you're going down right now this so this as you're going this way is pumping out sodium potassium and chloride but as this is going down what's going to be one of the components in here you're going to have a lot of water in this area so water loves to follow sodium chloride I told you that right where's that sodium and where's that chloride at it's out here in that medullary interstitial space so out here in this medullary interstitial space what's happening we're having a lot of sodium ions out here and we're having a lot of chloride ions pushed out here and if all of these guys are accumulating out in this area what's happening to this area is becoming very salty what's water going to want to do he's going to want to go to the areas of where salt is so where's water going to start flowing it's going to start flowing out into this area here by a type of obligatory watery absorption right now you might be wondering how does this water get out what are these blue channels now they didn't just draw them for no reason they have to have a specific type of name they do these channels here are called aqua pouring type one and the only reason I mention is that because we'll talk about the collecting duct and we'll talk about aquaporin two and three and four but aqua form one is these channels that are always open in the descending limb of the loop of Henle and as this actual filtrate is going down consisting of a lot of water what happens is as it's going down the a sending limb as it's going up it's pumping out so sodium potassium and chloride ions and the concentration of the salt is increasing in this area so as this is going down and this is going up it's making the medulla really really salty so what happens to the water it wants to move out of the descending limb and into this medullary interstitial space so you start losing water passively what does that call whenever as the a signaling is going up this way it's pumping out sodium potassium and chloride as it's going up it's doing that and while water is going down waters following the salt out into that modular interstitial space that mechanism is called it's right over here called D counter-current multiplier mechanism okay so one more time let's explain the counter crow multiplier mechanism as this actual filtrate is moving through this area I should mention something also you're probably wondering will Kant salt and stuff leave no because the actual descending limb of the loop of Henle is completely impermeable to solutes what does that mean that means salts can't go out and they don't really come in either okay so again one more time as this is actually flowing down the only thing that it's permeable to is water it's impermeable to solutes on the a sending limits the exact opposite it is completely impermeable to water but only permeable to solutes so what is it doing in this area here in the a sending limb its pumping out sodium potassium and technically to chloride ions right to chloride ions and as that's doing that it's pumping the sodium potassium into chloride ions in its area and making it really really salty and concentrated and very very hypertonic as the actual descending limb of the loop of Henle is going down what happens to the water it wants to be where the salt is so it leaves the descending limb and goes out into the medullary interstitial and what happens then if you're losing a lot of water what would it be let's say it takes this turn the filtrate takes the turn here and it's going to get ready to go into the ascending limb what do you think the osmolality will be in this area here it started off at 300 but then it gets saltier as you go down so technically if water was flowing out here let's say that it was let's say it was 300 right and it's almost about 300 there the water's going to want to flow out into this area where the sould is until it's about 500 million moles same thing here it's about 700 so waters going to want to flow out of the actual kidney tubular descending limb out into this area until the kidney tubules plasma osmolality is about 700 million holes right let's keep going down over here in this area it's going to be about 900 million Wells water's going to want to keep flowing out into this area until his osmolality in the kidney tubules equal to about what 900 million osmoles what do you think will continue to keep happening water will continue to keep going out into this medullary interstitial space until whenever it takes that turn and gets ready to go up it is now 1200 milliosmoles what is 1200 milliosmoles that a pretty high number I'd say this a lot so if it's a lot if it's a high osmolality what does that mean it's really really rich in its rich in a lot of solutes like sodium and chloride and very very low in water so we're going to say then that this plasma osmolality of the filtrate is now hypertonic to what hypertonic to the plasma osmolality of 300 milliosmoles okay now as we go up it's really really concentrated but then what does it do what it's in the ACE ending limb it's pumping out sodium potassium and chloride ions and it continues to pump out sodium and potassium and chloride ions when it goes away what was it pretty much pumping out it was only pumping out salt right sodium potassium - chloride anions no water was leaving it actually goes until when it actually moves up to this area it's almost equal to 300 milliosmoles it's approximately around like 200 million ohms about when it gets into the distal convoluted tubule so now again one more time it's going down it becomes at the end of it it becomes hypertonic why because you're losing a lot of water out into the medullary interstitial space why are you losing it because as the eighth-inning limb is taking the filtrate up it's pumping sodium potassium and two chloride ions out here do this co-transporter making the medulla really salty that's why you get the counter-current multiplier mechanism as it's going up though it's pumping the salt out so it loses a lot of salt or solutes so the osmolality when it gets up to this point here which is called the distal convoluted tubules it's a little bit less than 300 milliosmoles about like 200 okay what is that call whenever your eyes molality is really low let's look if the osmolality is really low that means that you don't have a lot of solutes and you have a little bit more water in that area than you do soils so we have a low osmolality that's referred to as hypotonic so now as the fluid leaves the a sending limb of loop of Henle it now is considered to be hypotonic with comparison to what the plasma osmolality of 300 milliosmoles okay and again it can range I could say really the range is about from 120 to about 200 millivolts really okay and I can then the filtrate we're going to the DCT which we'll talk about next but I got to talk about this guy now the vagus erecta so the Vaser recta is really important okay the VIS erecta is a branch of the peritubular cats actually a peritubular capillary in the medulla and so it's a branch of the efferent arteriole now we refer to the Vaes erecta as what's called the counter-current exchanger counter-current exchanger okay so let's go back to the osmolality what was it as we were moving down let's assume that was about 300 right here then as we move down and went to about 500 then as we go down a little bit more went to 700 then it went to 900 and then it goes to about 1,200 right so that's our renal medulla that's the the medullary interstitial gradient right the plasma osmolality gradient so you know blood flow through the Vasa recta is really really sluggish it's really really slow moving really really slow and as this blood is flowing through this area what's happened to the concentration is getting really really salty so what's really really high and concentration how you're going to of sodium ions in here you're going to have a lot of chloride ions in here right so as it goes down it picks up a lot of sodium chloride so it picks up a lot of sodium chloride and more and more sodium chloride as it's going down but at the same time if it's really really salty in this area and you know there's water coming from that area so there's going to be water where's water going to want to flow we've already talked about this it's going to want to flow from areas of low plasma osmolality right or Loas molality high osmolality where there's a lot of salt so water is going to come out here to where it's salty and if it's moving out here to where it's salty look what it's doing it's moving the water out and it's bringing sodium chloride in but then look what happens it makes this turn and it comes back up now as the plasma osmolality starts decreasing what are you going to want to do then you're going to want to get rid of the sodium chloride so now you're going to start pushing that sodium chloride out and when it leaves so it's about 300 going in so it's about 300 milliosmoles going in it's approximately about 325 millions moles leaving almost exactly equal so again you're pushing out the sodium chloride but look what else happens as you're going up the sodium chloride is actually going to get pushed out right it's actually going to pushed out the water is going to move back in okay so the water is going to move back in what is the significance of this the whole purpose of having the sodium going in the salt salt going in and the water going out going down the Vaes erecta and then the exact opposite occurring but while you're going up the Deseret where it's pushing the salt out and bringing the water in is because imagine this let's imagine all this area right here it's really really salty a lot of sodium a lot of chloride if we have a lot of like fluid coming through here and let's say it washes away that's sodium chloride you're not going to be able to maintain that nice medullary interstitial gradient so all this Vaes erecta are the counter current exchanger is doing is it's preventing the rapid removal of sodium chloride so it's not actually developing this medullary interstitial gradient or this counter-current multiplier mechanism right it's not the one generating it it's maintaining it so again one more time what is the function of the counter current exchanger as it's going down it's picking up salt and getting rid of water as it turns the corner and goes up it gets rid of the salt and brings in water and it takes a little bit more salt away what's the significance of this to prevent the rapid removal of sodium chloride from the medullary interstitial that you can maintain a nice gradient a nice salinity gradient okay that's one function you know what else it carries oxygen you know these cells they depend upon oxygen so he's also going to be delivering oxygen and certain types of nutrients to these tissue cells also so that's another function so two functions of the basal recta one is helps to maintain the medullary interstitial gradient by preventing the rapid removal of sodium chloride from this medullary interstitial and the second one is it provides oxygen to the tissue cells and again remember that the Vaser recta is a very very sluggish blood flow all right so let's go ahead and sum everything up then let's get this out of the way so let's go ahead and start with what's happening in the descending and what's happening in a sending so if you remember descending limb what was actually what was the whole purpose here remember that it was water permeable meaning that while it can move in or can move out right and it was solute impermeable so no salt can leave right so no salt can leave here so it's actually going to be water permeable solute impermeable now what were those proteins that were present within the actual membrane those were called aquaporin one so aquaporin one right and what was aquaporin one allowing for it was allowing for the water to move out where it into the medullary interstitial right so interstitial why was it moving out into the medullary interstitial because remember what was happening in the a sending limb and the a sending limb you had what you had that sodium potassium to chloride co-transporter and what was that sodium potassium to Clio transporter doing it was pumping sodium out it was pumping potassium out and it was pumping to chloride ions out out where out into the medullary interstitial if it pumps it out into the medullary interstitial what's it going to do to the magellan transition it's going to make it really salty if it's really really salty on that medullary interstitial as it's going up what you're going to do it's going to want to pull the water out into that area what does that call whenever the water moves out into the area of the medullary interstitial as it's going down well as the ascending limb was moving up it's actively pumping out that sodium potassium and the chloride that whole event is called the counter-current multiplier mechanism and who was maintaining this salinity gradient this salty gradient within the actual medullary inter station preventing the rapid removal of assault in providing oxygen to the tissue cells it was the Vasa recta or counter current exchanger oh and oh I actually told you I was going to tell you something about that potassium didn't I remember told that some of that potassium stays out here what happens is some of that potassium gets released out but what happens if some of that potassium actually gets pushed in to the lumen of the filtrate when it gets pushed in it creates a depolarization of the inner side of the membrane they sending limb what's present in this area is calcium and magnesium because there's a lot of positively charged or depolarization of this inner lining of the actual luminal membrane they can't move out they can't actually get out of this area usually they want to be able to get out of this area right what happens is because they're actually they're actually trying to get out into this area they get bounced around because of these positive charges right because they're repelled what eventually happens is they get bounced around boo boo boo boom and then move right through this area right here they actually move right in between these cells what does that call whenever the calcium and the magnesium moves in between the cells that's called para cellular transport so the calcium and the magnesium could also undergo reabsorption into this actual medullary interstitial space by para cellular route all right so we covered a lot of information guys a lot of stuff with respect to the loop of Henle we covered the counter-current multiplier mechanism the counter current exchange or a lot of different information I really hope all of it made sense I hope you guys enjoyed it if you guys liked it hit that like button subscribe leave any comments we'd appreciate it we really want to be able to help help you guys out and make a difference all right engineers until next time