the loop of Henley is massively important structure of the net front that not Onley, absorbs a lot of water and in salt, but also plays an important role in maintaining the osmotic Grady INTs of the kidney that are necessary for water and salt re absorption. Now the loop of Henle E connects the proximal tube you'll to the distal tube you'll and it goes in and out of the medulla. It kind of dips its loop into the medulla and then comes back out. And remember, depending on the depth to which the loop of Henle E enters the medulla. You know, you, uh, would classify in Effron is either cortical or Juckes. Tim Edgell earn Ephron, and the first part of Loop of Henley, the one that goes into the medulla that connects to the proximal convoluted tubules is known as the descending limb. And this is a thin portion, and it's permeable toe water and lots of water. Re absorption occurs here. This is going to cause the volume of the fill trait to decrease because it's losing lots of water. However, it's not re absorbing any salt Onley. Water is being re absorbed here that means that the solute concentration of the fill trait is going thio increase, so it's actually going to become a Mork concentrated Phil trait. The ascending limb has a thin section and a thick section, and basically within ephron, thin sections don't do active transport. Thick sections do active transport. That's the difference. You need a thicker tube, you'll in order to attach all those pumps and, you know, specialized structures to actively, um, transport molecules, whereas you want a thin structure when it's your mostly gonna be relying on passive transport. Because, remember, uh, the distance that something has to travel will affect its rate of diffusion. So the ascending limb starts off with passive transport in the thin section, and it's going to be re absorbing salt, and it's impermeable toe water on. Then the thick section will active actively re absorb salt and the whole the whole ascending limb is is impermeable to water, so Onley salutes will be reabsorbed. I'm saying salt, it's other salutes to It's just easier toe thio to just say salt. So, uh, here, because salutes air being re absorbed. But water is not. The volume won't change volumes going to stay the same, but we're diluting the fill trait because we're taking solids out. So the fill trait is concentrated in the descending limb and then diluted in the ascending limb because we're absorbing water on one side and salt on the other. Now, this actually is a special type of counter current exchange. We call a counter current multiplier system, which is basically a system that expends energy to create a strong concentration radiant that it's going to use for counter current exchange. The way this happens is the deeper you get into the medulla, the salt here, it iss water will flow out of the descending limb because of the osmotic Grady int created by the ascending limb. So this portion of the loop of Henley creates the Grady int necessary to re absorb water on this side. That's the counter current aspect to this, Um, because uhh just something to consider is that as the fill trait moves down the loop of Henle E, it gets more and more concentrated right, because it's going to lose water along the way because water is gonna be reabsorbed. But as the fill trait gets more and more concentrated, so does the osmotic radiant outside of the loop of Henle E. You know, that's the other aspect of this counter current system is that, you know, as as it requires a greater and greater Osma Larry T to re absorb the water. The medulla provides a saltier and saltier environment to accomplish that. So basically high solute concentrations, um, at the beginning of the ascending limb are what are going to drive solute transport. Because by the time the fill trait makes it here, it's going to be so super concentrated that when it moves into the ascending limb, where it's no longer permissible toe water and now permissible to salutes, the fill trait is going to be more concentrated, then the environment outside of it. And so it's going thio re absorb salt. Salt is going to move out of the fill trait into this super salty environment, and that's going to dilute the fill trait as it moves up the ascending limb. However, when it reaches this thick portion, it's like the Phil trait is to dilute, to be moved based on those osmotic radiance anymore. And that's why active transport is used in the last portion in order to keep re absorbing salt and maintain those osmotic radiance despite no longer being able to rely on passive transport. And finally, after that, you know long journey up and down the loop of Henle e Phil traits going to make it to the distal, convoluted tube you'll, which is almost the end of its journey. So let's flip the page.