Question

what is the formation of diluted urine

Answer 1

formation? as in how dilute differs from concentrated?

Answer 2

the process for the formation of dilute urine

Answer 3

The short answer is - you drink a lot of water, and your kidneys excrete a lot of said water, leaving you with dilute urine.

The long answer is - the large amount of water you ingested raises your blood pressure. This, in turn, is detected by interestingly - your heart. Specialized cells around the right atrium detect a raise in blood pressure and secrete Atrial Natriuretic Peptide. This, in turn, lowers the reabsorption of sodium (causing water to remain in the urine) by inhibiting the RAAS system.

The RAAS system, in short, stimulates the reuptake of sodium through a cascade of hormones.

Answer 4

so what part does the collecting duct and convoluted play in the formation?

Answer 5

Glad you asked. RAAS stands for Renin-Angiotensin-Aldosterone System.

The aldosterone that is secreted through the aforementioned cascade causes the collecting duct and distal convoluted tubule to reabsorb the sodium. ANP inhibits aldosterone secretion, thus causing the collectiong and distal convoluted tubule to absorb less sodium.

Going to verify that real quick...

Answer 6

It's worth mentioning - iirc, ANP also inhibits the secretion of vasopression, or ADH from the anterior pituitary. This is another hormone that regulates the kidneys - what it does is increase the number of aquaporins (water channels) in the collecting duct.

Answer 7

It's a lot to memorize...but in short - between these three systems, the bodye xercises a very detailed control over BP and blood concentration.

To summarize:
ANP - stimulus: High BP - result: inhibition of aldosterone and ADH = lower BP, more dilute urine

RAAS - stimulus: Low BP/ Low Blood Volume - result: increased reabsorption of sodium, constriction of blood vessels

ADH - stimulus: Low blood osmolarity - result: greater amount of aquaporins = less diluate urine, greater uptake of water

Sorry for blabbing so much. Bio's one of the few subjects in which I actually (somewhat) know what I'm talking about!

Answer 8

@kma230 ADH role in faithfull mice (and humans)?

Answer 9

Hi @fretje,

Could you explain what you meant by 'faithfull mice' for me please? Apologies - brain's working a bit slow today.

Answer 10

@kma230 ADH role in partner choice and promiscuity...

Answer 11

Very interesting - out of my expertise, but I'm reading into it now...it appears more faithful mice have greater amounts of ADH receptors in their brains.

Perhaps @BiomedStudent can shed some more light on this phenomena?

Answer 12

tanx kma230

Answer 13

@kma230 @Biomedstudent and if one drinks ethanol, it does something with dthe ADH as well, which makes change partner choice more often.

Answer 14

My response to this what WHO-BOY, it's COMPLICATED! You've gotten some good general info from others, so I'm going to bust out my old physiology book and verify that I still remember the mechanisms.

Convoluting tubules are the meat of urine concentration - they do all the heavy lifting (and the mechanism is CRAZY awesome, but way way way more complex than I ever understood). "In the absence of ADH the tubule is relatively impermeable to water, and additional reabsorbtion of solutes causes the tubular fluid to become even more dilute... this failure to reabsorb water and continued reabsorbtion of solutes lead to a large volume of dilute urine." (p217 of Guyon and Hall Pocket companion to Texbtook of Medical physiology"
The short version - the convoluting tubules keep on sucking out solutes, leaving water to move on out.

ADH, as mentioned above, controls the concentration, but the mechanism is up to the convoluting tubules to Resorb Less Water (netting you dilute urine).

Is that helpful?

Answer 15

@fretje Ethanol passes the bloodbrain barrier and affect brain directly, it also inhibits several metabolic pathway due to the excessive NADH+H from
Ethanol -> Alcohol dehydrogenase & Acyl dehydrogenase.
I doubt that ADH is the main component is promiscuity, if you happend to have any reference to a study performed i'd be happy to read it.

@eril12345 Kma230 has provide excellent and thorough answer to you question,
If you wish to read up on a example of chronically diluted urine you can read up on "Diabetes insipidus"