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9

Probably because it's easier to retain what the body wants than get rid of what the body doesn't want. What does your body want to keep from your Urine? Pretty much water and selective ions (Cl-, K+, Na+, Ca+2, etc.). Maybe a few other things, depending on how healthy you are. Now, what does your body want to get rid of in your Urine? Well, anything it ...


7

The fact that urine output (enuresis) and other kidney functions are circadian is well known, just search on pubmed 'circadian urine kidney'. This can be due both to the fact that liquid consumption is less during the night and to the fact that hormones regulating kidney function like aldosterone and plasma angiotensin II are circadian.


5

The problem is that real organs are just damn complex - yes the kidney's prime role is just to be a filter, but in order to do so it must be plugged in to a dozen regulation mechanisms - osmotic balance, ion management, protein management and a plethora of more subtle ones. Moreover it is a part of body, so it must also follow all the standard protocols to ...


3

The previous answer isn't quite correct, because, well, blood flow is complicated and the body has autoregulatory mechanisms. As Alex mentioned, vasoconstriction doesn't occur in capillaries because they lack a muscle layer. It does occur in the small arterioles before and after the glomerulus (the afferent and efferent arterioles, respectively). ...


3

I would argue from an evolutionary perspective: not all kidneys are created equal. The mammalian kidney has a long evolutionary history and potentially a lot of phylogenetic inertia. Mammals do what they can with what they inherited from their ancestors. The metanephric kidney, which is what mammals have, is thought to have evolved with the first amniotes ...


2

The phosphoric acid in cola will contribute to dietary intake of phosphate. I may be missing something, but, since the transporter functions to reabsorb phosphate that has been filtered out at the glomerulus, excess phosphate will spill over into the urine. According to Wikipedia the RDA for phosphorus is 700 mg and the tolerable upper intake level is 4000 ...


2

I would suggest a couple of papers Circadian rhythms in urinary functions: possible roles of circadian clocks? - Noh et al., Int Neurourol J., 2011 Circadian regulation of renal function - Firsov and Bonny, 2010 Neural regulation of the circadian vasopressin rhythm in cerebrospinal fluid: a pre-eminent role for the suprachiasmatic nuclei - Schwartz and ...


1

To my knowledge, capillaries in general and the renal capillaries in glomeruli in particular do not have muscle cells to constrict. The latters have only a basal layer with podocytes lying directly on it (link to the open textbook). Therefore, the vasoconstriction takes place only in arterioles before the glomeruli, and this vasoconstriction leads to the ...



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