# Ignorant questions about the digestive system **URL:** \ **Category:** Factual Questions\ **Created:** [August 16, 2013, 6:50am UTC](https://boards.straightdope.com/t/ignorant-questions-about-the-digestive-system/666392 "2013-08-16T06:50:10Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Eleusis](https://avatars.discourse-cdn.com/v4/letter/e/f4b2a3/32.png) [@Eleusis](https://boards.straightdope.com/u/Eleusis)\ **Post date:** [August 16, 2013, 6:50am UTC](https://boards.straightdope.com/t/ignorant-questions-about-the-digestive-system/666392/1 "2013-08-16T06:50:10Z")
Hi all- Am I correct in my understanding that all urine was previously in the bloodstream, prior to being filtered out by the kidneys and/or liver? So if I’m dehydrated, and take a big stinky yellow piss, that was all in my blood? … and when the large intestine absorbs water from our feces, does that water then directly enter the bloodstream? Thanks ---
**Author:** ![Pjen](https://avatars.discourse-cdn.com/v4/letter/p/3d9bf3/32.png) [@Pjen](https://boards.straightdope.com/u/Pjen)\ **Post date:** [August 16, 2013, 7:23am UTC](https://boards.straightdope.com/t/ignorant-questions-about-the-digestive-system/666392/2 "2013-08-16T07:23:48Z")
> [@Eleusis](#): > > Hi all- > > Am I correct in my understanding that all urine was previously in the bloodstream, prior to being filtered out by the kidneys and/or liver? So if I’m dehydrated, and take a big stinky yellow piss, that was all in my blood? > > … and when the large intestine absorbs water from our feces, does that water then directly enter the bloodstream? > > Thanks Yes and yes. ---
**Author:** ![Pjen](https://avatars.discourse-cdn.com/v4/letter/p/3d9bf3/32.png) [@Pjen](https://boards.straightdope.com/u/Pjen)\ **Post date:** [August 16, 2013, 7:25am UTC](https://boards.straightdope.com/t/ignorant-questions-about-the-digestive-system/666392/3 "2013-08-16T07:25:37Z")
Just add that the liver is not part of the urinary system. ---
**Author:** ![Snerky\_Snerk](https://avatars.discourse-cdn.com/v4/letter/s/6bbea6/32.png) [@Snerky\_Snerk](https://boards.straightdope.com/u/Snerky_Snerk)\ **Post date:** [August 16, 2013, 12:03pm UTC](https://boards.straightdope.com/t/ignorant-questions-about-the-digestive-system/666392/4 "2013-08-16T12:03:10Z")
With the urine, I’m assuming you mention the liver because you may have heard that it produces urea? If so, that’s correct, but there’s no dedicated link between the liver and kidneys to transport it. The urea is released into the bloodstream and is extracted by the kidneys for disposal. Cells produce waste amino acids -\> into blood -\> liver packages them up as urea -\> into blood -\> filtered out in kidneys -\> bladder. Note: I ain’t no doctor, just a pre-pre-med student. If I’ve made any errors, corrections are most welcome. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 16, 2013, 1:10pm UTC](https://boards.straightdope.com/t/ignorant-questions-about-the-digestive-system/666392/5 "2013-08-16T13:10:22Z")
And to just add that the urinary system isn’t part of the digestive system, either. ---
**Author:** ![Eleusis](https://avatars.discourse-cdn.com/v4/letter/e/f4b2a3/32.png) [@Eleusis](https://boards.straightdope.com/u/Eleusis)\ **Post date:** [August 16, 2013, 3:47pm UTC](https://boards.straightdope.com/t/ignorant-questions-about-the-digestive-system/666392/6 "2013-08-16T15:47:12Z")
Thanks all ---
**Author:** ![picunurse](https://avatars.discourse-cdn.com/v4/letter/p/7bcc69/32.png) [@picunurse](https://boards.straightdope.com/u/picunurse)\ **Post date:** [August 16, 2013, 3:51pm UTC](https://boards.straightdope.com/t/ignorant-questions-about-the-digestive-system/666392/7 "2013-08-16T15:51:46Z")
The urine, itself, was never in your blood. The parts that make up the urine were. The kidneys manufacture the urine by are fairly complicated process. Water and electrolyes are transported back and forth across membranes until the correct amount of each are available for the body to function. For example, If you have normal kidneys and you eat too much salt, but drink plenty of water, your kidneys will move all of the salt out of the blood, then retrieve the amount of salt the body needs to function. The rest is part of the urine that travels from the [glomerus](http://faculty.stcc.edu/AandP/AP/AP2pages/Units24to26/urinary/filtrati.htm) to the [calyces](http://www.google.com/imgres?imgurl=http://www.healthcentral.com//common/images/1/1101_2775_5.jpg&imgrefurl=http://www.healthcentral.com/diabetes/more-images-7588-146.html&h=320&w=400&sz=23&tbnid=Cxr9ujjjWImXyM:&tbnh=90&tbnw=113&prev=/search%3Fq%3Dkidney%2Banatomy%26tbm%3Disch%26tbo%3Du&zoom=1&q=kidney+anatomy&usg=__fZTVKboQVyMeUqLcUHDs5xc2XHM=&docid=_ch7y68O1gn-BM&sa=X&ei=8kgOUtqELKe7iwKvyoDgDg&ved=0CDEQ9QEwAQ&dur=5892), then to the renal pelvis, on to the ureters, then the bladder, and out through the urethra. There are other desolved chemicals that the kidneys filter as well. The two links may give you a better idea how the kidneys work. If not just google kidney function and you’ll find several discriptions.