Renal-Chapter 29 Flashcards
What are the ranges of urine osmolarity in cats and dogs?
Dog: 50-2400 mOsm/L
Cat:50-3300 mOsm/L
An increase in ADH would have what effect on urine?
More concentrated urine
A decrease in ADH would have what effect on urine?
More dilute urine
Give renal mechanism for excreting dilute urine (normal conditions)
-Does body excrete xs amount of solutes?
After water ingestion, 30 min later, it gets absorbed.
Urine flow rate increase
Urine osmolarity decrease
Excretion of a large volume of dilute urine
Total amount of solute excreted and plasma osmolarity remain relatively constant. Body does not excrete xs amount of solutes.
Give renal mechanism of dilute urine excretion when ADH levels are very low
-What parts are sensitive to ADH?
Tubular fluid remains isosmotic in PT
Descending LOH tubular fluid becomes more concentrated as it flows into the inner medulla
Ascending LOH tubular fluid is diluted (regardless if ADH is present or not)
Tubular fluid in DT and CT is further diluted in the absence of ADH
CT are sensitive to ADH
ALOH is not sensitive to ADH
In general, how do kidneys conserve water if there is water deficit?
Excrete concentrated urine
Excrete solute and reabsorb water
Which species would have higher urine osmolarity threshold? Beavers or desert species. Why?
Desert species=10,000 mOsmoles/L
Beaver- 500 mOsmoles/L
Desert species have a higher urine concentrating capacity and more juxtamedullulary nephrons to converse water in drier environment.
How much concentrated urine must a human excrete a day?
-What does excretion consist of?
600 mOsm
- Waste products of metabolism
- Ingested solutes
What is formula for obligatory urine volume?
Mandatory concentrated urine to be excreted/Maximum urine concentrating ability
The higher the concentrating ability, obligatory urine volume is
Higher or lower?
Lower`
If you drank 1 L sea water of 1200 mOsm/L how would you compensate for that?
Automatically have to get rid of 600 mOsm/L but you’ve ingested 1200 mOsm of NaCl water.
600+1200= 1800 mOsmol to get rid of
1800/1200 (max urine concentration ability)
You’ve have to drink 1.5 L of water to compensate dehydration.
What does urine specific gravity measure?
estimates urine solute concentration ability
How is urine specific gravity different from osmolarity?
Specific gravity takes into account the number and SIZE of the solute molecules.
What can alter urine specific gravity?
Large molecules like glucose and AB can give false results suggesting that the urine is very concentrated
What are normal values of urine specific gravity for humans, dogs, cats
Humans: 1.002-1.028
Dog:1.001-1.070
Cat:1.001-1.080
Requirements for excreting concentrated urine
High level of ADH
High osmolarity of the medullary interstitium
Why does there need to be a high level of ADH for excreting concentrated urine?
ADH causes water reabsorption at a greater rate than solute reabsorption thus creating concentrated urine
Why is a high osmolarity of medullary interstitium necessary for excreting concentrated urine?
Interstitium osmolarity of cortex=300 mOsm/L
medulla=1200-1400 mOsm/L (more concentrated)
Osmotic gradient necessry for water reabsorption…
Use countercurrent mechanism
T/F Concentrated urine depends on the anatomical arrangement of LOH
True
T/F Collecting ducts move through medulla and contain filtrate from single nephron
Contains filtrate from multiple nephrons
Thin descending LOH
- Does it have active transport of Na+
- Is it permeable to water, NaCl, and Urea
- No active transport
- Permeable to water, NaCl, urea (everything is normally passive
Thin ascending LOH
- Is there an active transport for NaCl
- Is it permeable to water, NaCl, urea?
- No active transport to NaCl
- Impermeable to water
- Permeable to NaCl and urea
Thick ascending LOH
- Does it have active NaCl transport***
- Is it permeable to water and urea?
- Has active NaCl transport capable of establishing a 200 mOsm/L concentration grandient
- Impermeable to water and urea
Explain how the countercurrent multiplier system in LOH produces hyperosmotic renal medulla
As fluid moves through the loop, Na and Cl is pumped out of the ascending limb raising interstitial fluid osmolarity UP TO 200 mOsm/L GRADIENT.
Water then moves from descending LOH by osmosis and concentrates filtrate.
This repeats until ma is reached (~1200 mOsm/L) at deepest medullary point.
When do cortical collecting ducts become high permeable to water?
After passage through LOH
and HIGH ADH levels
Explain role of collecting ducts in excreting concentrated urine
Water is reasborbed into cortical interstitium and carried away by peritubular capillaries
Most of water reabsorbed in corte helps preserce medullary interstitial osmolarity
Further water reabsorption in medulla but small compared to cortex.
T/F Urea contributes to the hyperosmotic renal medullary interstitium. If so when?
T
About 40 percent (500 mOsm/L)
When kidney forms maximum concentrated urine
How is urea reabsorbed in MCD?
Stimulation of ADH
Urea will be passively reabsorbed by facilitated diffusion through urea transporters
T/F DT and CCD are permeable to urea
F
They are impermeable
Outline the flow of urea through tubules when ADH is high
50 percent is immediately reabsorbed (at proximal tubule)
Concentration increases through LOH and water is reabsorbed faster
DT/CCD impermeable to urea but water moves out
Since ADH is present, MCD is permeable to urea
Urea diffuses down concentration gradient into interstitial fluid and re-enters and recirculates to help maintain concentration gradient