Countercurrent Multiplier System

by Thad Wilson, PhD

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    So now, let’s move on to the countercurrent multiplier. How do you utilize having both these cortical collecting ducts, these nephron loops, and these blood vessels all right at the same spot? How is that going to allow for this gradient to occur? I’m going to through the theory of the countercurrent multiplier first, and this sets up the reason why we have the gradient. Does it ever really occur in the body? Well, maybe not. But this is how the process is set up to start. Once it’s started, you will continue to have this process go over and over again until the gradient develops, but this is just assuming that you start off with no gradient. But you will always have a little bit of a gradient, so it’s a little bit artificial. But unless we go through the theory of it, you will never really know how this gets established. So let’s start off prior to the multiplication process occurring. Let’s assume that the thin descending limb, where the fluid is first traveling into, is 300 milliosmoles. It’s going to travel down through the tube, through the hairpin loop, and then back up again through the thin ascending limb. All of them are 300 milliosmoles. We have to have a starting place. What happens is, as you start to enter the thick ascending limb, there’s active transport of sodium. So you start kicking out sodium into the interstitium. There’s also sodium leaving via the thin ascending limb. So in this condition, we’re going to have now movement of sodium from the ascending limb into the interstitium. We call this a single effect. So we’re moving some of the sodium out of the ascending limb. What this does is concentrates the sodium in the interstitial fluid. It doesn’t...

    About the Lecture

    The lecture Countercurrent Multiplier System by Thad Wilson, PhD is from the course Renal Physiology.

    Included Quiz Questions

    1. Firstly Sodium is released in the interstitium
    2. Firstly water will be released into the interstitium
    3. Sodium will release after water release
    4. Water is released through thin ascending limb
    5. Sodium is released through thin descending limb
    1. Movement of Sodium in the interstitium
    2. Movement of water in the interstitium
    3. Development of osmotic gradient
    4. Fluid displacement
    5. Creation of iso-osmotic environment

    Author of lecture Countercurrent Multiplier System

     Thad Wilson, PhD

    Thad Wilson, PhD

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