Why do we urinate? (semi-serious thread)

[Knicks]

We have trillions of cells in our bodies.

We drink water for those cells.

Do we urinate because we drink more molecules of water than the # of cells we have?

GFR and intravascular volume status determine urination, right? So we basically urinate to get rid of waste.

But don't ALLLLLLL those cells in our bodies need that water? or is it surplus?

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[KeyzerSoze]

First, remember that we don't just drink water, we make it; it's a product of oxidative phosphorylation.

 

[45408]

But don't ALLLLLLL those cells in our bodies need that water?

To do what?

 

[Iapyx]

To do what?

To carry out photosynthesis of course (obviously a little light helps too)

🙄

 

[Slowpoke]

I love these questions, I ask them all the time myself, in curiosity, and attempt to put a valid big picture explanation.

So the explanation that I would conjure up, which is void of heavy scientific proof and lies mainly on logic and basic biology from school is this:

Amazingly, we have two outlets for waste (your butthole, and peehole)

Why then do we need two outlets, couldn't we just function on one?

Not necessarily, one outlet is for cellular waste (cells secrete out "waste" into the sewage pipes and is filtered later by the kidneys). The other one is for food waste, the organic matter/foreign material that is of no use for us.

Now the outlet for cellular waste is dependent on your sewage pipes (veins/arteries/etc.) which is partially made up of water.

The water within your pipes need to be isotonic with your blood cells so that they do not rupture/shrink.

So one logical conclusion is that we urinate to regulate the water within our blood stream (sewage pipes) to stabilize our blood cells.

So to integrate this into the big picture. After the cells in your body are adequately hydrated, the excess is found in the sewage pipes waiting to be peed onto toilet seats all across the world.

So I believe you are correct, we pee because we just have too much water (explains the observation of "clear pee when we drink a lot of water, yellow pee when we drink too little water")

 

[thechad]

We have trillions of cells in our bodies.

We drink water for those cells.

Do we urinate because we drink more molecules of water than the # of cells we have?

GFR and intravascular volume status determine urination, right? So we basically urinate to get rid of waste.

But don't ALLLLLLL those cells in our bodies need that water? or is it surplus?

The more you post, the more I think you may have some sort of cognitive disability...

 

[richse]

We have trillions of cells in our bodies.

We drink water for those cells.

Do we urinate because we drink more molecules of water than the # of cells we have?

GFR and intravascular volume status determine urination, right? So we basically urinate to get rid of waste.

But don't ALLLLLLL those cells in our bodies need that water? or is it surplus?

I don't know how serious you are but I'm reading physio stuff so I'm gonna answer anyway. I would say the main reason we must excrete water is not that we have a surplus of water. It's the waste we need to get rid of that will hold at least a minimum amount of water in the lumen due to osmotic forces. Additionally, there's no way we could have a perfect reabsorption system so loss of non-waste (e.g. electrolytes) will drag some water out too. I guess if we had no waste products then theoretically we wouldn't need to urinate. Even then though, we'd still have to drink to replace the loss of water through the bowel.

 

[PMPMD]

Also, it's fun.

 

[richse]

Also, it's fun.

I could do without it during long surgeries, flights, and movies though.

 

[PMPMD]

I could do without it during long surgeries, flights, and movies though.

Yeah, I've definitely had to re-consider my love for caffeine when I'm in a long case.

 

[Isoprop]

The answer is evolution. Our ancestors evolved to fit a specific terrestrial niche where the urination increased fitness. Note if we lived in a more watery environment, we might be expelling nitrogenous waste via ammonia and if we required to conserve more water as possible, we would have different kidneys/nephrons to concentrate our urine or use uric acid and expel it with our feces (eg reptiles).

 

[Knicks]

To do what?

I'm a little surprised that a resident is asking this. (no offense, honestly)

I love these questions, I ask them all the time myself, in curiosity, and attempt to put a valid big picture explanation.

So the explanation that I would conjure up, which is void of heavy scientific proof and lies mainly on logic and basic biology from school is this:

Amazingly, we have two outlets for waste (your butthole, and peehole)

Why then do we need two outlets, couldn't we just function on one?

Not necessarily, one outlet is for cellular waste (cells secrete out "waste" into the sewage pipes and is filtered later by the kidneys). The other one is for food waste, the organic matter/foreign material that is of no use for us.

Now the outlet for cellular waste is dependent on your sewage pipes (veins/arteries/etc.) which is partially made up of water.

The water within your pipes need to be isotonic with your blood cells so that they do not rupture/shrink.

So one logical conclusion is that we urinate to regulate the water within our blood stream (sewage pipes) to stabilize our blood cells.

So to integrate this into the big picture. After the cells in your body are adequately hydrated, the excess is found in the sewage pipes waiting to be peed onto toilet seats all across the world.

So I believe you are correct, we pee because we just have too much water (explains the observation of "clear pee when we drink a lot of water, yellow pee when we drink too little water")

haha, props for that input 😀

The more you post, the more I think you may have some sort of cognitive disability...

Fantastic post.

I don't know how serious you are but I'm reading physio stuff so I'm gonna answer anyway. I would say the main reason we must excrete water is not that we have a surplus of water. It's the waste we need to get rid of that will hold at least a minimum amount of water in the lumen due to osmotic forces. Additionally, there's no way we could have a perfect reabsorption system so loss of non-waste (e.g. electrolytes) will drag some water out too. I guess if we had no waste products then theoretically we wouldn't need to urinate. Even then though, we'd still have to drink to replace the loss of water through the bowel.

Says right there in the thread title that I'm semi-serious 🙂 And thanks for the input. 👍

 

[yamaraja808]

to carry out photosynthesis of course (obviously a little light helps too)

🙄

View attachment ManFlowerCostume.jpg

 

[richse]

View attachment 16973

Does that picture make anyone else think of rectal prolapse? I think that picture with the hookworms from lecture is burned into my mind forever.

 

[45408]

I'm a little surprised that a resident is asking this. (no offense, honestly

I'm not surprised that you don't recognize the Socratic method, honestly.

 

[DrVanNostran]

I love these questions, I ask them all the time myself, in curiosity, and attempt to put a valid big picture explanation.

So the explanation that I would conjure up, which is void of heavy scientific proof and lies mainly on logic and basic biology from school is this:

Amazingly, we have two outlets for waste (your butthole, and peehole)

Why then do we need two outlets, couldn't we just function on one?

Not necessarily, one outlet is for cellular waste (cells secrete out "waste" into the sewage pipes and is filtered later by the kidneys). The other one is for food waste, the organic matter/foreign material that is of no use for us.

Now the outlet for cellular waste is dependent on your sewage pipes (veins/arteries/etc.) which is partially made up of water.

The water within your pipes need to be isotonic with your blood cells so that they do not rupture/shrink.

So one logical conclusion is that we urinate to regulate the water within our blood stream (sewage pipes) to stabilize our blood cells.

So to integrate this into the big picture. After the cells in your body are adequately hydrated, the excess is found in the sewage pipes waiting to be peed onto toilet seats all across the world.

So I believe you are correct, we pee because we just have too much water (explains the observation of "clear pee when we drink a lot of water, yellow pee when we drink too little water")

Don't forget we lose a good amount of water from expiration and sweat.

 

[jdh71]

The answer is evolution. Our ancestors evolved to fit a specific terrestrial niche where the urination increased fitness. Note if we lived in a more watery environment, we might be expelling nitrogenous waste via ammonia and if we required to conserve more water as possible, we would have different kidneys/nephrons to concentrate our urine or use uric acid and expel it with our feces (eg reptiles).

This is really a non-answer.

Why do I get a boner? Why do I like to take a crap? Why do I see in colors?

*drum roll*

EVOLUTION!!!!

Ummmmmm . . . duh? We had to get here somehow and evolution is the generally accepted method of that occurring, but it doesn't answer WHY any of it occurs.

Though I think you do get points for the most low hanging fruit in this thread.

 

[dr zaius]

Volume homeostasis? Acid-Base homeostasis? Osmotic homeostasis?

 

[iamcool]

If we are drinking too much water, we would need to urinate to get rid of excess water.

But even if we are not drinking too much water, we would still need to urinate to get rid of toxic waste. Water acts as a solvent to dissolve these substance.

If the above does not make sense then you can think of it this way. hydrophilic wastes are going to drag water out with it as it leaves. Hydrophobic substances are going to be oxidized to get maximum amount of ATP. And once oxidized, they become hydrophilic just like urea.

 

[thechad]

Fantastic post.

Ditto.

 

[Geekchick921]

My first thought... Aren't kidney stones made up of some of the same substances that we pass in our urine? If all you're worried about is the water, I'd much rather pee those compounds out in a solution of water on a daily basis than pass kidney stones regularly.

 

[richse]

My first thought... Aren't kidney stones made up of some of the same substances that we pass in our urine? If all you're worried about is the water, I'd much rather pee those compounds out in a solution of water on a daily basis than pass kidney stones regularly.

I'm guessing from your signature that there's no way you're coming to jefferson. That's too bad for jefferson, I remember reading your profile a while ago and hoping you'd end up here.

 

[shaggy alfresco]

Yea I chose Jeff over temple and I'm bummed I won't be classmakges with geekchick 🙁.

 

[FIREitUP]

I was hoping this was going to be like that book "Everyone Poops". Alas, I am disappointed once again.

 

[Geekchick921]

I'm guessing from your signature that there's no way you're coming to jefferson. That's too bad for jefferson, I remember reading your profile a while ago and hoping you'd end up here.

Aww, thank you! That's really nice of you to say. Jeff was my first choice going in, then I let my nerves get the better of me at my interview (my first one) and wound up getting HPWL'ed. Then I feel in love with Temple at interview day, they accepted me straight-out, and they gave me a sweet scholarship to boot.

Yea I chose Jeff over temple and I'm bummed I won't be classmakges with geekchick 🙁.

🙂 Maybe we'll cross paths at Abington or something, since both Jeff and Temple students can do clerkships there.

 

[thepoopologist]

I was hoping this was going to be like that book "Everyone Poops". Alas, I am disappointed once again.

You read it? Me too!

 

[newdoc2013]

birds dont pee. they poo - they havean extra enzyme that allows them to convert nitrogenous wastes to uric acid (insoluble in h2o) from urea (soluble in h2o) - an enzyme we lack (although we do produce uric acid from base metabolism). then, instead of peeing it out of a tube with a lot of water like us, they push it into their cloaca and poo it out with the rest of the solid waste.

 

[richse]

Aww, thank you! That's really nice of you to say. Jeff was my first choice going in, then I let my nerves get the better of me at my interview (my first one) and wound up getting HPWL'ed. Then I feel in love with Temple at interview day, they accepted me straight-out, and they gave me a sweet scholarship to boot.


🙂 Maybe we'll cross paths at Abington or something, since both Jeff and Temple students can do clerkships there.

We generally have some inter-med school mixers and normally MS1/MS2's from Jeff, Temple, Drexel, Penn, and PCOM will come. I'm sure you guys could meet up at one of those. Third year for me so I doubt I'll be getting out much.

 

[CaptainSSO]

There are WASTES we have to excrete. Nitrates, urea, etc. Main role of the kidneys is to filter the blood, and we have to piss out the waste.

This is really a non-answer.

Why do I get a boner? Why do I like to take a crap? Why do I see in colors?

*drum roll*

EVOLUTION!!!!

Ummmmmm . . . duh? We had to get here somehow and evolution is the generally accepted method of that occurring, but it doesn't answer WHY any of it occurs.

Though I think you do get points for the most low hanging fruit in this thread.

Very good point.

 

[FIREitUP]

You read it? Me too!

It's required reading for a PHD in meconium.

 

[cowme]

Why do we urinate?

-to ostracize the kid who can't handle stress at a young age and pees his pants
-to mess with the passed out dude by putting his hand in a bowl of warm water
-so girls can drive their boyfriends insane every 20 minutes on a long car drive
-so people like bear grylls have jobs
-golden showers

And the most important:

To write stuff in snow

 

[rihdus]

We urinate to get rid of poisonous ammonia from our body (nitrogen) and the best way to do that is to produce urea, which has a large amount of nitrogen:molecule ratio. Urea is water-soluble, hence the water in our urine.

 

[Cailyn Brown]

We have trillions of cells in our bodies.

We drink water for those cells.

Do we urinate because we drink more molecules of water than the # of cells we have?

GFR and intravascular volume status determine urination, right? So we basically urinate to get rid of waste.

But don't ALLLLLLL those cells in our bodies need that water? or is it surplus?

You are right Knicks!

Urinary system filters waste and extra fluid from the blood. Body takes nutrients from food and uses them to maintain all bodily functions including energy and self-repair. After body has taken what it needs from the food, waste products are left behind in the blood. These wastes are removed as a type of waste called urea from the blood. Hence called urinary system.

There are lot of other systems and disorders associated with Urinary System. The following site would help you in knowing the complete description about the human urinary system.

http://kidney.niddk.nih.gov/kudiseases/pubs/yoururinary/

Thanks