Health and medicine
- Meet the kidneys!
- Kidney function and anatomy
- Glomerular filtration in the nephron
- Changing glomerular filtration rate
- Countercurrent multiplication in the kidney
- The kidney and nephron
- Secondary active transport in the nephron
- Introductory urinary system quiz
- Intermediate urinary system quiz
- Advanced urinary system quiz
Changing glomerular filtration rate
Created by Raja Narayan.
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- How come people with infections have hematuria if there is a basement membrane preventing RBCs from entering the filtrate?(13 votes)
- It can be caused by damage to the bladder or ureter itself causing blood to leak into the urinary tract. Things that may cause this are UTIs ans kidney stones. Also in hemolytic diseases, broken down blood cell particles may be able to pass through the basement membrane causing to urine to have red coloration.(36 votes)
- I think I understand the effects on filtration with respect to the diameters of the afferent and efferent arterioles. However, I'm not sure if it was actually mentioned whether the efferent arteriole has a smaller diameter than the afferent arteriole. Does the afferent arteriole have a larger diameter than the efferent arteriole?(9 votes)
- Yes, the efferent arteriole has a smaller diameter, which makes sense because much of the plasma's volume was filtered into Bowman' s capsule so it doesn' t need to be as large as the afferent arteriole. However much of the water, electrolytes and nutrients are soon 're-absorbed in the proximal convoluted tubule. Since arterioles have smooth muscle they can also dialate and constrict to autoregulate GFR of the nephron.(7 votes)
- In the endothelial cells there are holes where the waste leaves, correct? If this is true, I was just curious as to if there are diseases or sicknesses because of the holes being too big or too small and what they're called.(3 votes)
- Yes, there are "holes". The more correct way of saying that there are holes is that they are "fenestrated" (coming from the latin word "window"). A common misconception is that there are holes between the cells. Actually there are holes IN the cells.
As far as I can tell, I've looked online and it doesn't seem like there are any diseases out there, but I could be wrong since I'm not a med student!
I suspect that sizes won't make a huge difference because the basement membrane is semi permeable too, so is like a secondary filter, and should be a back up if the endothelial cells go wrong.(4 votes)
- Do you need both kidneys to live?(2 votes)
- One kidney can do the work of two, but it takes longer.(4 votes)
- Why do people pee?(1 vote)
- The same reason we poop, to get rid of waste products that can harm the body.(5 votes)
- May I ask where do the numbers in the Harris-Benedict equation for calculating BMR arise from?
Also what about the number 140 in Cockcroft-Gault equation for calculating creatinine clearance?(2 votes)
- I am not sure. If you look up the paper where they first propose the equation, you'll get your answer.
In my opinion, it will mostly be an outcome of a multivariable regression. These numbers come form the observed data, what coefficients for the various variables best predict say the creatinine clearance. Although the factors that actually affect these numbers will be complicated, they are not "derived"as you would expect the coefficient of an equation to be.(2 votes)
- Is there a video where he talks about these kidney diseases mentioned at the very end?(2 votes)
- I searched and did not find a KA video on kidney disease. Renal artery stenosis is discussed at the US National Institute of Diabetes and Digestive and Kidney Diseases website
There is much of kidney disease at this site, see the index at
- If you can't absorb enough nutrients in the digestive system, could it overwhelm the kidney's later on?(2 votes)
- why does it named efferent arteriole, why not named by efferent venule, i mean it already passthrough the glomerulus ?(1 vote)
- Arterioles have more smooth muscle then venules and regulate the blood flow by constricting and relaxing that smooth muscle. Therefore, the flow into and out of the glomerulus is managed by the afferent and efferent arterioles that change the glomerular filtration rate. It is an arteriole.(2 votes)
- ‘’Arterial” in subtitles = “Arteriole”?(1 vote)
- In this video, he is talking about the unusual arrangement (for the body) where an afferent arteriole connects to a capillary bed called the glomerulus and then that connects to another arteriole, the efferent arteriole. Usually, the afferent arteriole connects to capillaries and then then connect to a venule, or little vein.
So in the kidneys the advantage having of these muscular arterioles on either side of the glomerulus is they can manage the blood flow and pressure through the glomerulus, thereby managing blood pressure and the removal of urea waste. In the transcript of this video, it does not consistently say arteriole, although it should, it is all about arterioles. This is a mistake you are absolutely right.
Arterial = pertaining to an artery, a large diameter blood vessel.
Arteriole = a small diameter muscular blood vessel coming off an artery just before a capillary, that permits or prevents perfusion of the capillary bed.
Voiceover: All right, so I think we have a pretty good appreciation of how we have some smaller ions, amino acids, glucose and even water than can leak through these fenestrations and get into this space right here. Remember, this is just Bowman's space. They can get into Bowman's space where we can then process them into the rest of the nephron. This is Bowman's space, and we have these podocytes that hug the arterioles right here by holding on to the endothelial cells. We also have this basement membrane that prevents giant proteins in our red and white blood cells from leaking through. And we have these tubule cells that help line the other side, and they're epithelial cells, they're in the class of epithelial cells. Excellent. Now the last thing I want to cover is what's happening here from having an arterial go into a structure and then give off another arterial. That's a little weird, right, because we usually like thinking about arterioles going into capillaries and then giving out a venule. Well one way to think about this is sort of like a marathon where there are a lot of people running on the same street from point A to point B, and they're either running in a narrow street or a wide street. Let's make a table to think about this. What would happen if we look at our afferent and our efferent arterioles, and we change the diameter of the vessel. What does that do to the rate of filtration? We'll write filtration right here. How does the diameter of our vessels change the rate of filtration? If we increase the diameter of the afferent arterial, or if we have a very wide path that allows a lot of marathon runners to run into the glomerulus, that means there's going to be a lot of blood here that includes all of the ions, and the amino acids and glucose, in addition to our blood cells and giant proteins we talked about. There's going to be a lot of stuff over here. So if there's a lot of stuff running over these fenestrations you're going to have a lot of leakage, and so there's going to be a lot of filtration. More filtration occurs if there are more people or more marathon runners running into this space right here, so more filtration. What about if we did that with the efferent arteriole? Let's say we increase the diameter of the efferent arteriole so there's space for more marathon runners to run away from this very narrow street, or this place where a lot of people can run off the pavement and get into these holes and go elsewhere. If we increase the diameter of our efferent arterial and allow people to leave, they're not going to be able to stay around here for a long period of time, they're not going to be near these fenestrations. That means that our filtration rate will decrease, because the blood is moving away from the place that it would be filtered. The same thing goes if we decrease the diameter of our afferent arteriole. If we decrease the amount of runners or blood that can come into the glomerulus, that means there's going to be less fluid filtered out, so a lower filtration rate. This is actually what happens with renal artery stenosis. If we have a very narrow or stenosed vessel - that's what stenosis means, it's just narrow - renal artery, that means there's going to be less blood that branches off and goes to our afferent arteriole. There's going to be less blood that runs across our fenestrations and is filtered away. On the flip side, if we decrease the diameter of our efferent arterial that makes it difficult for our runners to leave this fenestrated vessel, so there's going to be some backup, there's going to be a lot of ions and amino acids and glucose hanging around here near these holes. If blood backs up that means so do these guys, so then they're going to be filtered through these holes and collected into Bowman's space, so our filtration rate will increase, it will increase because there's a lot of backup that allows more time for filtration. Maybe if you're interested in learning about kidney diseases later on there's a lot of stuff that tweaks this system, that messes around with the afferent arterial or the efferent arterial, sort of like what I talked about for renal artery stenosis. I encourage you to think about what can go wrong with this process and how things can change, that's kind of the best way to learn about it. That's how our glomerulus works. Let's move on to the next part of our nephron.