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    does water leave through the proximal convoluted tubule or is it impermeable to water?
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    (Original post by celina10)
    does water leave through the proximal convoluted tubule or is it impermeable to water?
    The water is able to leave the proximal convoluted tubule as it is permeable to water A part of the nephron that is impermeable to water would be the ascending limb of the Loop of Henle, for example!
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    (Original post by zef1995)
    The water is able to leave the proximal convoluted tubule as it is permeable to water A part of the nephron that is impermeable to water would be the ascending limb of the Loop of Henle, for example!
    But more water is reabsorbed by the collecting ducts right?
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    (Original post by celina10)
    But more water is reabsorbed by the collecting ducts right?
    Surprisingly not, as much as some water is reabsorbed in the collecting ducts and in the Loop of Henle, from what I've read about 65% of water is reabsorbed in the proximal convoluted tubule!

    I hope that's helpful
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    (Original post by zef1995)
    Surprisingly not, as much as some water is reabsorbed in the collecting ducts and in the Loop of Henle, from what I've read about 65% of water is reabsorbed in the proximal convoluted tubule!

    I hope that's helpful
    Oh so the collecting ducts just control how much extra water is reabsorbed, and thanks
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    (Original post by celina10)
    Oh so the collecting ducts just control how much extra water is reabsorbed, and thanks
    In a way, yes! Have you been taught about osmoregulation yet? If the water potential of the blood is too high, less ADH is released into the blood, causing less water to reabsorbed in the collecting duct - overall leading to more dilute urine.
    The opposite goes for when the water potential of the blood is too low. Osmoreceptors in the hypothalamus detect this, and more ADH is released into the blood. The ADH molecules bind to complimentary receptors on the walls of the collecting duct, making the walls more permeable as aquaporins form in the membrane. As the walls are more permeable, more water is selectively reabsorbed and urine is more concentrated.

    You're more than welcome I hope your exam goes well!
 
 
 
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