The Kidney - Water reabsorption

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  • Created by: Steff06
  • Created on: 01-03-16 17:51
How much fluid is filtered from blood per minute?
Around 125 cm3.
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How much fluid is left after selective reabsorption?
45 cm3
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What is the role of the loop of Henle?
To create a low, negative water potential in the medulla tissue.
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Why is this low water potential needed?
To ensure even more water can be reabsorbed from the fluid in the collecting duct.
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Describe the structure of the loop of Henle?
Consists of a descending limb that descends into the medulla and an ascending limb that ascends back into the cortex.
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What does the arrangement of the loop of Henle allow?
Sodium and chloride ions to be transferred from the ascending limb to the descending limb.
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What is the overall effect of the countercurrent multiplier mechanism?
To increase the concentration of salts in the tissue fluid as they diffuse out of the ascending limb.
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How is this negative, low water potential achieved?
By loss of water by osmosis to the surrounding tissue fluid and by diffusion of sodium and chloride ions into the tubule from the surrounding tissue fluid.
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What is the purpose of the loop of Henle?
To reabsorb water from the filtrate.
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How does the loop of Henle reabsorb water?
By creating a gradient of hypertonicity(increasing salt conc)in interstitial tissue of the medulla.Tissue becomes increasingly concentrated, moving down medulla from cortex end towards pelvis. Gradient achieved through countercurrent multiplier.
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What is the difference between the descending and ascending limb in terms of mOsm?
The descending limb is always 200 mOsm less.
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What happens in the ascending limb?
Sodium and chloride ions are actively transported from the ascending limb into interstitial tissue of the medulla.
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The thick portion of the ascending limb is?
Impermeable to water
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What is the thin portion of the descending limb impermeable and permeable to?
Relatively impermeable to sodium and chloride and permeable to water.
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What is the aim of the fluid?
To achieve a concentration gradient as it moves around.
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What is the maximum concentration?
1200 mOsm. This is due to the length of the loop.
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What is the function of the loop of Henle?
To create a high concentration of sodium and chloride ions in the interstitial tissue of the medulla.
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Why does this high concentration of salts need to be achieved?
To allow water to be reabsorbed from the contents of the nephron as it passes through the collecting duct.
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What survival advantages may this have?
Produces very concentrated urine. Conserves water and prevents dehydration as much as possible.
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Other cards in this set

Card 2

Front

How much fluid is left after selective reabsorption?

Back

45 cm3

Card 3

Front

What is the role of the loop of Henle?

Back

Preview of the front of card 3

Card 4

Front

Why is this low water potential needed?

Back

Preview of the front of card 4

Card 5

Front

Describe the structure of the loop of Henle?

Back

Preview of the front of card 5
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