Renal Physiology: Overview - Video Tutorials & Practice Problems
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concept
Overview of Renal Physiology
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This video is just gonna be a general overview of renal physiology. Now, I'm gonna preface this by saying that people often assume that the way that kidneys make urine is by just taking all the bad stuff out of our blood. And then that's what becomes the urine, but it's actually not like that at all. It's more like kidneys take almost everything out of our blood, then they have to put all the good stuff back into the blood. And then the leftovers of that process are what ends up being our urine. So it's much more complex than, than those people initially think. And nephrons are gonna be carrying out three distinct physiological processes to help us get to that end goal of creating urine. So our first process is called glomerular filtration. And this is the actual formation of the filtrate. Now, as we kind of alluded to in our video on the renal corpuscle, what's happening here is that blood pressure basically forces water and other solutes out of those leaky permeable capillaries and into that capsular space and then that fluid is gonna be called filtrate. So as you can imagine this is happening mainly within our glomerular capsule which we have um drawn for you here in purple. So that, so that's our first step. It's just making the filtrate. Next, we have our tubular reabsorption. So, tubular reabsorption is the process of reclaiming essential substances from the filtrate. And when I say essential substances, I mean, things like water, electrolytes, like sodium and potassium, nutrients like glucose. You know, we don't wanna lose all of that to urine, right? We wanna keep that, that's that, that stuff's really good for us. We we need that. So, reabsorption is a really, really important process and I'll give you um some context in a second or just how intensive the process of reabsorption can actually be. But again, what's basically happening here is that this is the selective transport of substances back into our bloodstream. So we're um transporting them from the filtrate back into the bloodstream. Now, reabsorption is gonna is gonna be happening mainly in our proximal tubule and our Nephron loop. But we will see some reabsorption in the distal tubule and collecting duct as well. You can see here in our image, we've colored basically the entire renal tubule and collecting duct in green. But our proximal tubule and Nephron loop are in this darker green to indicate that, that, that that is where most reabsorption is happening. But again, we're gonna see some of that in our distal tubal and collecting duct as well. And then our final process is tubular secretion. So, tubular secretion for the most part happens simultaneously with tubular reabsorption, but they are very distinct processes. The tubular secretion can help us maintain an electrolyte and acid based balance. And it can also help us remove any toxins or drugs from the blood that were not originally filtered for whatever reason. And tubular secretion is often considered the opposite of reabsorption. So remember, reabsorption is when we basically take substances from the filtrate and put them into blood tubular secretion is gonna be taking substances from the bloodstream and putting them into the renal tubule or putting them into the filtrate. They're literal opposites of each other. And secretion is going to be happening within our proximal tubule distal tubule and our collecting duct which you can see we have colored on all of those here in blue for you. And as you can see, there is no secretion happening in the Nephron loop. The Nephron loop is just gonna be doing reabsorption. Now, to give you some context again, for how intense this process can be. Our kidneys process about 100 and 80 L of blood derived fluid every single day. That means that we're making about 47 gallons of filtrate every day and about 1.5 L of that will actually leave the body as urine. So that can be like approximately 1% or even less than 1% actually turns into urine. So you can see how intense this process of reabsorption actually needs to be. It's about 99% of the filtrate has to go back into the blood. So um very, very fun stuff we're gonna learn all about it. I'm very excited to take this journey with you and I will see you guys in our next video. Bye bye.
2
example
Renal Physiology: Overview Example 1
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58s
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OK. So the main purpose of tubular reabsorption is to what? So remember, the point of reabsorption is to literally reabsorb all of the essential good substances that ended up in the filtrate. We wanna pull them back into our bloodstream. So looking at these choices, our answer is going to be b it's to help us reclaim important substances from our filtrate. Remember that creating filtrate happens in step one in glomerular filtration. By the time we get to tubular reabsorption, the filtrate has already been created and then it can't be c because tubular reabsorption actually helps us decrease urine volume. So if we were not reabsorbing water, for example, all that water would end up in our urine, meaning we'd have a much higher urine volume. The reabsorption helps us to decrease urine volume if anything. So that's why the answer can't be C and our answer here is B.
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Problem
Problem
Tubular secretion occurs in the…
A
Glomerular capsule only.
B
Proximal tubule, distal tubule, and collecting duct.
C
Glomerular capsule, proximal tubule, distal tubule, and collecting duct.
D
Proximal tubule, nephron loop, distal tubule, and collecting duct.
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