Formation of Dilute and Concentrated Urine (Nursing)

by Jasmine Clark, PhD

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    00:00 So now let's look at how we form dilute versus concentrated urine.

    00:06 The formation of the medullary gradient is going to allow for us to make concentrated urine, which is going to be more concentrated than our normal blood osmolality of 300 milliosmoles.

    00:22 First when we are over hydrated, we're going to produce large volumes of diluted urine.

    00:29 This is under hormonal control where the antidiuretic hormone production will decrease this will lead to urine that is about 100 milliosmoles or a third of our blood osmolality.

    00:44 Additionally, if aldosterone is pregnant, then we're going to reabsorb ions, and this is going to create even more dilute urine.

    00:55 When we are dehydrated, we produce a small volume of concentrated urine.

    01:02 Antidiuretic hormone is released which will cause us to make very concentrated urine.

    01:09 At maximal antidiuretic hormone levels our urine can be as much as 1200 milliosmoles, which is the highest osmolality we find in our medullary gradient.

    01:23 Under conditions of severe dehydration about 99% of the water in our filtrate will be reabsorbed producing an extremely concentrated urine.

    01:36 So if we take a look at this diagram, we see the differences between over-hydration and which we are not activating our antidiuretic hormone and dehydration where we're going to activate the maximum amount of antidiuretic hormone that we can.

    01:55 With no antidiuretic hormone, all of the water is able to be excreted in our urine and we're going to have a very dilute urine but with maximal antidiuretic hormone, we're going to insert as many aquaporins in the collecting duct as possible in order to reabsorb any water that's in the filtrate and producing a very concentrated urine.

    02:21 Urea is another substance that is going to help us form the medullary gradient inside the renal medulla.

    02:29 Urea is going to enter the filtrate in the ascending thin limb of the nephron loop by way of facilitated diffusion.

    02:39 Cortical collecting duct is then going to reabsorb water leaving the urea behind.

    02:46 And the Deep medullary region, we now have a highly concentrated urea which leaves the collecting duct and then enters the interstitial fluid of the medulla.

    02:57 Urea, then moves back into the ascending thin limb and we're going to start the process all over again.

    03:04 This is going to contribute to the high osmolality found deeper in the medulla of the kidney.

    03:13 Diuretics are going to be chemicals that are going to enhance our urinary output.

    03:19 These include things like antidiuretic hormone inhibitors, like alcohol, sodium reabsorption inhibitors, like caffeine or drugs that you would take for high blood pressure or swelling, Loop Diuretics, that are going to inhibit the formation of the medullary gradient and osmotic diuretic, which are substances that are not reabsorbed so water will remain in the urine and said of being reabsorbed with the substances.

    03:50 For example, in diabetic patients high glucose concentrations will pull water from the body and has a diuretic effect.

    About the Lecture

    The lecture Formation of Dilute and Concentrated Urine (Nursing) by Jasmine Clark, PhD is from the course Urinary System – Physiology (Nursing).

    Included Quiz Questions

    1. Maximal antidiuretic hormone (ADH) release and near complete water reabsorption
    2. Minimal antidiuretic hormone (ADH) release and complete salt and water filtration
    3. Minimal aldosterone release and decreased salt resorption
    4. Minimal antidiuretic hormone (ADH) release with complete salt filtration
    1. Urea
    2. Angiotensin
    3. Antidiuretic hormone (ADH)
    4. Aldosterone
    1. Caffeine
    2. Alcohol
    3. Mannitol
    4. Furosemide

    Author of lecture Formation of Dilute and Concentrated Urine (Nursing)

     Jasmine Clark, PhD

    Jasmine Clark, PhD

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