Renal 6 Flashcards

1
Q

Normal function requires ECF Osmolarity =

A

300

mOsm

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2
Q

H2O and Na+ input via diet:

A

– Too much

– Not enough.

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3
Q

H2O and Na+ loss: (4)

A

– Insensible
– Sweat
– Feces
– Urine - To a large extent, kidneys balance the
books by adjusting water reabsorption and
excretion.

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4
Q

Mechanisms to eliminate excess water by excreting a

A

dilute urine;

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5
Q

Mechanisms to conserve water by excreting a

A

concentrated urine;

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6
Q

Renal feedback mechanisms that control the

A

extracellular fluid sodium concentration and osmolarity

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7
Q

Thirst and salt appetite mechanisms that determine the
intakes of (2), which also help to control
extracellular fluid volume, osmolarity, and sodium
concentration

A

water and salt

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8
Q
Concentration and Dilution of the Urine
Accomplished 
independently of major 
changes in solute 
excretion:
– Maximal urine concen-
tration:
– Minimal urine concen-
tration:
A
1200 mOsm (specific 
gravity ~ 1.030).
50 mOsm  (specific 
gravity ~ 1.003).
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9
Q

Filtrate is — in proximal tubule.

A

isosmotic

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10
Q
Filtrate is isosmotic in proximal tubule.
 Becomes hyperosmotic as passes 
through tDL (2)
A

– Water reabsorption

– No solute reabsorption.

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11
Q

Becomes hyposmotic as passes

through TAL and early distal tubule (2)

A

– Solute reabsorption

– No water reabsorption.

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12
Q

Osmolarity of fluid will vary as pass
through distal tubule and collecting
duct (2)

A

– Stays hyposmotic in absence of
ADH (dilute urine)
– Dilute Urine (as low as 50 mOsm/L)

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13
Q

Urine Formed With ADH is Concentrated (4)

A
 ADH increases H2O permeability 
of distal tubule and collecting 
duct.
 Large volume of H2O diffuses 
into interstitium.
 Enters capillaries of Vasa Recta 
and removed.
 Creates concentrated urine (as 
high as 1200 mOsm/L)
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14
Q

Obligatory Urine Volume

A

 The maximal concentration ability of the
kidney dictates how much urine volume
must be excreted each day to rid the body of
metabolic waste products and ions that are
ingested.

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15
Q

Adult must excrete — mosmol daily
(solutes ingested and [mainly] produced by
metabolism).

A

600

(600 mosmol/day)/(1200 mosmol/L) = 0.5
L/day.

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16
Q

(600 mosmol/day)/(1200 mosmol/L) = 0.5
L/day.
– Adds to

A

other sources of H2O loss (skin,

lungs, GI).

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17
Q

Renal disease impairs — ability:

A

concentrating

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18
Q

Requirements for Excreting a Concentrated

Urine (2)

A
  1. High levels of ADH

2. Hyperosmotic medullary interstitial fluid

19
Q

Hyperosmotic medullary interstitial fluid (4)

A

Surrounds collecting duct
Sets gradient for water reabsorption
Requires Counter Current Multiplier Mechanism
Function of Juxtamedullary nephrons

20
Q

Function of Juxtamedullary nephrons (3)

A
  • Long Loop of Henle
  • Vasa Recta
  • Slow flow rate
21
Q

High Interstitial fluid Osmolarity a result of: (4)

A
  • Active transport of Na+ and other ions by ascending limb of LOH
  • Active transport of ions from collecting duct into interstitium
  • Facilitated diffusion of Urea by Inner medullary collecting ducts
  • Movement of only small amounts of water into medullary
    interstitium
22
Q

Continuous delivery of NaCl from proximal convoluted tubule into

A

loop of Henle

23
Q

Concentration of filtrate by H2O reabsorption by

A

Descending Limb of Henle

24
Q

Continuous reabsorption of solute into interstitium by

A

thick ascending limb

25
Na+-K+ pumps in CD pump Na+ into interstitium to
↑ osmolarity (to ≈1,200 mOsm/l) => formation of interstitial osmolar gradient
26
In Absence of ADH (2)
 Reabsorb solute |  Little to no water reabsorption
27
n Presence of ADH (3)
```  Distal tubule and collecting ducts become highly permeable to water and reabsorb much water into cortical interstitium  Medullary collecting duct cells reabsorb water but overall amounts much lower (keeps medullary interstitium from being diluted).  Reabsorbed water carried away by Vasa Recta ```
28
Role of Urea in Concentrating Urine
Waste product of protein metabolism; produced continuously by liver.
29
urea: | Normally excrete --% of filtered load
20-50
30
urea: Non---, but constitutes an osmotic load that must be --- (mw = 60 g/mol; plasma level 5 mM).
toxic | excreted
31
urea: Contributes ---% of medullary interstitial osmolarity (500-600 mOsm/L)
40-50
32
Reabsorbed passively by --- collecting duct cells
medullary
33
Secreted into descending limb and thin ascending limb of Loop of Henle - Requires: ADH (2)
Concentrates urea in filtrate (water reabsorption in cortical and medullary collecting ducts) Activates carriers (UT-A1; UT-A3) for the facilitated diffusion of urea by medullary collecting duct cells
34
Countercurrent Multiplier Mechanism |  Depends on anatomical relationships of (3)
loop of Henle, vasa recta, & collecting ducts.
35
~25% of nephrons are ---, with long loops of Henle that extend into renal medulla parallel to vasa recta & collecting ducts.
juxtamedullary
36
Filtrate in descending & ascending limbs of loop of Henle flows in opposite directions of blood flow in
Vasa Recta
37
Clears Reabsorbed water so does not dilute
medullary interstitial fluid
38
Blood flow only --% of total but sufficient for O2 supply and CO2 removal
2
39
Tubule Segment: Proximal Tubule % H2O Reabsorbed Filtrate Osmolarity
70 | Isosmotic
40
Tubule Segment: Descending LOH % H2O Reabsorbed Filtrate Osmolarity
20 | Hyperosmotic
41
Tubule Segment Ascending limb of LOH % H2O Reabsorbed Filtrate Osmolarity
0 | hyposmotic
42
Tubule Segment: Late DT and CCD % H2O Reabsorbed Filtrate Osmolarity
variable (adh) | variable
43
Tubule Segment: MCD % H2O Reabsorbed Filtrate Osmolarity
variable (ADH) | variable