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Loop of Henle and other Questions

Discussion in 'MCAT Study Question Q&A' started by futuredoctor10, Jan 5, 2009.

  1. futuredoctor10

    Classifieds Approved 10+ Year Member

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    For an individual with highly concentrated urine, filtrate entering the loop of Henle is likely to be more concentrated than filtrate exiting the loop of Henle.
    Why? If the descending loop of Henle allows water to passively diffuse OUT of the loop into the interstititum, wouldn't you want filtrate entering the loop of Henle to be less concentrated?

    That way, more water can passively leave in the descending loop and you could concentrate the urine more in the ascending loop.

    Also I found these statements online and everything sounds correct. If anything looks wrong please post! Thanks!

    If you have a long loop of Henle (ie desert rat), you can make your interstitium really salty and reabsorb almost all your water. This will concentrate the urine.

    The thick ascending limb is impermeable to water allowing the area outside of the tubules (interstitium) to become concentrated and the area inside the tubule to become dilute.

    The ascending part is necessary to concentrate the interstitium with salt/ions, creating a concentration gradient so that WATER can be absorbed in the descending part.

    Anti-Diuretic Hormone (ADH) works on the collecting duct of the kidney.
    My question: only on the collecting duct?
     
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  3. rocuronium

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    Most questions like this could be answered through a simple internet search. It would save you some time on writing out new posts. :p

    ADH (vasopressin) does indeed work in places other than the kidney. Take a read through this: http://en.wikipedia.org/wiki/Vasopressin
     
  4. Charles_Carmichael

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    For your ADH question, ADH causes the insertion of aquaporins in the late distal tubule and the collecting duct, not just the collecting duct.

    For the loop of Henle question, I'm not exactly sure what you're asking for. The filtrate entering the loop of Henle is usually around the same osmolarity as the plasma (300 mOsm); ie. it's isoosmotic. The filtrate leaving the loop of Henle and entering the distal tubules is hyposomotic. The descending loop is permeable to both water and Na while the ascending loop is impermeable to water and the thick ascending loop is permeable only to Na (and thus, Cl). The countercurrent multiplication in the loop depends on the NaCl reabsorption in the ascending part and the counter-current flow (notice how it loops down and does a hairpin turn to loop back...the filtrate is moving in opposite directions in each part).

    So, in the thick ascending loop, NaCl is reabsorbed but not water; this dilutes the filtrate so that the filtrate reaching the distal tubule is hypoosmotic. The collecting duct is where urine is concentrated, not the loop of Henle. Water leaves from the filtrate as it travels through the latter part of the distal tubule and the collecting duct. Remember, with the loop of Henle, the osmolarity of the interstitial fluid at the hairpin turn is around 1200 mOsm...so as the collecting duct passes through the interstitial fluid, the urine becomes concentrated to 1200 mOsm (the concentration of urine is dependent on the osmotic gradient set up by the loop of Henle...I think in humans, urine can only be concentrated around 4 times the concentration of the plasma because the loop of Henle creates an osmotic gradient that is 4 times more concentrated than plasma at the hairpin turn). Hope this helps.

    PS. Gleek is right about the internet search. Also, you've been asking a lot of physiology related questions...I would recommend checking out a textbook from the library or something so you can look up anything you're iffy about and get more thorough answers than you would on here. Good luck. :)
     
  5. engineeredout

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  6. futuredoctor10

    Classifieds Approved 10+ Year Member

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    Yep you guys are right! I have been asking questions everyday, I think I need to spend some time with the physio text or online sources.

    Thanks to all who responded. I did not intend to annoy anyone! :)
     
    #5 futuredoctor10, Jan 5, 2009
    Last edited: Jan 5, 2009

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