Excretion System (kidney Question)

[flin5845]

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I am getting tripped up on the wording when talking about the flow through the nephron. Here is what I am thinking, can anyone tell me if this is correct

Filtration- passive and nonselective, Filtration is when glucose,salts,vitamins and waste enter through the afferent arteriole into the glomerulus.

Secretion- active and selective, occurs in the proximal and distal tubules. I do not quite understand what is being "secreted" and where to. I think it is more toxins that did not initially get filtered, and they are being secreted INTO the tubules. (I am not sure though)

Reabsorption- passive, active, selective. Where solutes like glucose, vitamins, water get reabsorbed into the kidney.

Excretion- removal of waste.

I am mainly confused on what the secretion part is. Also I just was thinking about the flow and where the urine is most and least concentrated.

Most concentrated- proximal convoluted tubules sine this is where the most amont of molecules are present.

least concentrated- collecting duct since all the reabsorption has taken place.

Are all my assumptions correct?

 

[FROGGBUSTER]

I am getting tripped up on the wording when talking about the flow through the nephron. Here is what I am thinking, can anyone tell me if this is correct

Filtration- passive and nonselective, Filtration is when glucose,salts,vitamins and waste enter through the afferent arteriole into the glomerulus.

Secretion- active and selective, occurs in the proximal and distal tubules. I do not quite understand what is being "secreted" and where to. I think it is more toxins that did not initially get filtered, and they are being secreted INTO the tubules. (I am not sure though)

Reabsorption- passive, active, selective. Where solutes like glucose, vitamins, water get reabsorbed into the kidney.

Excretion- removal of waste.

I am mainly confused on what the secretion part is. Also I just was thinking about the flow and where the urine is most and least concentrated.

Most concentrated- proximal convoluted tubules sine this is where the most amont of molecules are present.

least concentrated- collecting duct since all the reabsorption has taken place.

Are all my assumptions correct?

Well, the proximal tubule is where the most amount of active re-absorption takes place, so it's probably more concentrated in the Bowman's capsule than it is there. The concentration also increases as you head deeper and deeper down into the loop of Henle as water flows out into the interstitial fluid in response to the increasing concentration gradients. And there is an increase in concentration again as you move from the distal tubule down the collecting duct because urea will passively flow into the interstitial fluid as the urine moves down the collecting duct, as well as the huge amounts of water re-absorption there.

There's multiple components that are secreted into the tubules, but I think one of the main things is acid. IIRC, it happens in both the proximal and distal tubules, although I could be wrong.

I don't think the DAT will test too deeply into this stuff though.

 

[PooyaH]

Reabsorption is when you move things (e.g. ions or water) from the tubular lumen to peritubular capillaries and secretion is when you take things from the peritubular capillaries to tubular lumen for excretion.

You do about 80% of your reabsorption of filtered solute in the proximal tubules. There is also about 25% reabsorption (mainly Na) in the loop of Henle, and about 8% reabsorption in the distal convoluted tubules and collecting duct. These are all active! Reabsorption of water is always passive and it happens in all three places (in the distal convoluted tubules and collecting duct, it is regulated by ADH).

Na, K, Ca, or P could be secreted OR reabsorbed in your kidneys depending on what your body needs at the time.

 

[flin5845]

thanks guys,

This is kinda off topic but I thought it was cool. I found online (so I took it with a grain of salt) that when you drink alcohol, it inhibits the secretion on ADH. Since ADH plays an important role in reabsorbing water, and if inhibited you can not uptake water. This is why you pee so much if you drink a lot I think. From this I was assuming if there is an inadequate amount of water removed from the large intestine, the feces becomes very liquidly and results in "party mud."

This is just something I was thinking but I am not quite sure if it is all true because I am not quite sure how the excretion system and digestive system connect in this idea because I know that the microvilli absorb the nutrients into the blood which then would go through the kidneys. So I am not quite sure if my party mud thinking is right, which might be bad......I need to study more

 

[PooyaH]

thanks guys,

This is kinda off topic but I thought it was cool. I found online (so I took it with a grain of salt) that when you drink alcohol, it inhibits the secretion on ADH. Since ADH plays an important role in reabsorbing water, and if inhibited you can not uptake water. This is why you pee so much if you drink a lot I think. From this I was assuming if there is an inadequate amount of water removed from the large intestine, the feces becomes very liquidly and results in "party mud."

This is just something I was thinking but I am not quite sure if it is all true because I am not quite sure how the excretion system and digestive system connect besides blood, which might be bad......I need to study more haha

You're on the right track. Alcohol is, in fact, a diuretic!