Renal 7: Renal Mechanisms for Concentration/Dilution of Urine Flashcards
(48 cards)
Where is the major site in which solute and water are separated?
Henle’s Loop
What value is the plasma osmolality held at?
300 mOsm/Kg H2O
What is antidiuresis?
state of dehydration that is typical for land dwellers.
What is the state of the following during antidiuresis? ADH water reabsorption urea reabsorption urine
Increased
Increased
Increased
Decreased (low volume high concentration urine)
What is diuresis
state of over-hydration. atypical and caused by administration of hypotonic solutions.
What is the state of the following during water diuresis? ADH water reabsorption urea reabsorption urine
Decreased
Decreased
Decreased
Increased (high volume, low concentration urine)
What is the osmolality of the following with respect to the plasma?
renal cortex
outer medulla
inner medulla
Renal Cortex: Isotonic
Outermedulla: mild hyperosmolality
Inner Medulla: strong hyperosmolality
What are the 3 major species and their % contribution to the gradient that contribute to the inner medullary hyperosmolality?
Na+(25%) Cl-(25%) urea (50%)
Rank the following from most to least hyperosmotic with respect to plasma:
outer medulla
inner medulla
renal cortex
inner medulla > outer medulla > cortex
What are the 3 mechanisms that generate and regulate medullary hyperosmolality?
Countercurrent Multiplier: generates initial osmotic gradient
Urea Cycle: Strengthens osmotic gradient
Countercurrent Exchanger: maintains osmotic gradient
What happens to the osmolality of the medullary interstitium during water diuresis?
reduced due to increased vasa recta blood flow and entry of some urea into collecting duct
No ADH so collecting duct is impermeable to water
What happens to the osmolality of the medullary interstitium during antidiuresis
Max ADH levels -> collecting duct highly permeable to water
Medullary interstitial gradient maxed
What is the countercurrent multiplier?
countercurrent flow in the 2 limbs of Henle’s loop that results in differential fluid and solute movements, generating vertical osmotic gradients
The thin descending loop of Henle has high/low water permeability, high/low salt permeability, and water/salt moves out of tubule.
high water permeability
low salt permeability
water moves out of tubule
The thin ascending loop of Henle has high/low water permeability, high/low salt permeability, and water/salt moves out of tubule
low water permeability
high salt permeability
salt moves out of tubule
What is the difference in salt movement between the thin and thick ascending limbs?
Thin: passive movement
Thick: active salt pumping
Where is the most active salt pumping site in the kidney?
Thick ascending loop of Henle
What part of the loop of Henle has high water perm. but low salt. perm.
Thin descending loop
What part of the loop of Henle has low water perm. but high salt. perm
Thin ascending loop
The thick ascending loop of Henle is diluting/concentrating segment. It becomes hyper/hypo-osmotic
Diluting segment
Hypoosmotic
Impermeable to water
What occurs in the distal tubule?
increased water permeabilty and salt transport -> reabsorption
What happens in the lower collecting duct but not the upper collecting duct?
Urea reabsorption
In the collecting duct, salt reabsorption is active/passive, and water reabsorption is active/passive.
active salt reabsorption
passive water reabsorption under ADH control
What occurs in the collecting duct?
active salt reabsorption and passive water reabsorption
