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Session 3 Flashcards

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1
Q

What does the vasa recta do

A

Absorb nutrients and solutes

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2
Q

Corticopapillary gradient is established by

A

Countercurrent multiplication (solutes)
Urea recycling

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3
Q

Corticopapillary gradient is maintained by

A

Vasa recta

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4
Q

What happens as you go down the descending limb of loop of henle

A

Increase in solute concentration, decrease in osmolality

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5
Q

The loop of Henle over view

A
  • Responsible for 25% Na+ reabsorption
  • Thin descending limb: permeable to water, Na+ and Cl-
  • Thin ascending limb: impermeable to water, minimal Na+ and Cl- transport
  • Thick ascending limb: impermeable to water, Na+K+2Cl- co transporter apical membrane
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6
Q

What happens at thick ascending limb for concentrated urine

A

Na+ pumped out
Osmolarity increases in interstitium due to gain of sodium
Osmolarity decreases in thick ascending limb due to loss of sodium

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7
Q

What happens as a result of sodium being pumped out of thick ascending limb

A

Filtrate in descending limb must equilibrate until osmolarity is same inside and outside

Water leaves LOH and Na+ and Cl- enter - tubular fluid becomes more concentrated

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8
Q

Overall result of loop of henle countercurrent multiplication

A

Vasa recta plasma descends in opposite direction to tubule
Always has lower osmolality
Always diffusion gradient from tubule to interstitium and interstitium to plasma

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9
Q

Thick ascending limb of Loop of Henle can maintain a difference of

A

200mOsm/kg between interstitium and tubular fluid

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10
Q

Loop of Henle normal plasma osmolality

A

300mOsm/kg

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11
Q

Maximum osmolality of interstitium

A

1400mOsm/kg

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12
Q

Fluid leaving LOH is

A

Hypotonic (100mOsm/kg)

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13
Q

5 features of vasa recta

A
  • Hairpin arrangement- permeable to solutes and water
  • Descend: absorb solutes, water lost
  • Ascend: loss of solutes, reabsorb water
  • Slow flow: can equilibrate at each stratification level and minimise washout
  • Absorbs water released from CD in presence of ADH (maintains high osmolality of interstitium)
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14
Q

What does urea recycling do

A

Help to maintain the medullary hypertonicity

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15
Q

How much urea is reabsorbed in proximal convoluted tubule

A

50% filtered urea re absorbed

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16
Q

What happens to tubular concentration of urea as it goes from medulla into lumen in descending limb

A

Increases as it diffuses down concentration gradient (110% at base of LOH)

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17
Q

What happens to urea at ascending limb

A

Ascending limb and early DCT impermeable to urea to concentration increases as solutes and water reabsorbed

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18
Q

ADH causes

A

Urea transporter UT1 to increase expression. Urea flows down conc grad. 70% filtered urea reabsorbed by UT1 and 40% excreted

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19
Q

How is urea recycled

A

Urea secreted back into LOH and goes back up to DCT/CD and is recycled

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20
Q

What do diuretics do

A

Act on the kidney to increase the production of urine and to eliminate water from the body

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21
Q

3 main things diuretics do as a result of eliminating water

A
  • Reduce plasma volume and cardiac output
  • Reduce blood pressure
  • Reduce oedema/ascites
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22
Q

What are diuretics

Study These Flashcards
A

Drugs that increase renal excretion of sodium and water resulting in increase in urine volume

23
Q

What is diuresis

Study These Flashcards
A

Process of excretion of water in the urine

24
Q

What is Natriuresis

Study These Flashcards
A

Process of excretion of sodium in the urine

25
5 main classes of diuretics
- Carbonic anhydrase inhibitors - Osmotic diuretics - Loop diuretics - Potassium sparing diuretics - Thiazide and thiazide-like diuretics
26
How do most diuretics act
By interfering with the normal sodium reabsorption by the renal tubules resulting in Na+ and water excretion
27
Which diuretics act at proximal tubule
Carbonic anhydrase inhibitors Amiloride a little bit SGLT-2 inhibitors (not diuretics)
28
Which diuretics act at ascending limb of loop of Henle
Loop diuretivcs
29
Which diuretics act at distal convoluted tubule/ early collecting duct
Thiazide and thiazide-like diuretics (Amiloride)
30
Which diuretics act at collecting duct
Potassium sparing diuretics
31
How do carbonic anhydrase inhibitors work
Proximal tubule, stop bicarbonate being converted into water and carbon dioxide, this inhibits sodium transport out
32
What do SGLT-2 inhibitors (Flozins) do
Reduce Na+ absorption in PCT
33
Osmotic diuretics key points
Mannitol- administered via IV Increase water excretion with relatively little effect on Na+ (water diuresis)
34
Effects of osmotic diuretics
Expands the extracellular fluid volume initially, decrease blood viscosity, inhibit renin release, increase renal blood flow
35
Uses of osmotic diuretics
Acute renal failure due to shock or trauma Acute drug poisoning- need to eliminate drugs that are reabsorbed from renal tubules To lower intracranial and intra ocular pressure before ophthalmic or brain procedures
36
Side effects of osmotic diuretics
37
What do loop diuretics work on
Prevent Na+K+2CL- transporter, reduce resorption of magnesium and calcium too
38
What are the most potent diuretics (high ceiling)
Loop diuretics- bumetanide and Furosemine
39
Key points of loop diuretics
Given orally or IV Fast onset of action Increase urine volume Suitable for emergency situations
40
When are loop diuretics useful
- Severe oedema associated with congestive heat failure, nephrotic syndrome - Treatment for Oliguric ARF - Treatment of hypercalcaemia - Acute pulmonary oedema - Acute hyperkalaemia, hypercalcaemia - Toxicity of Br, F, and I
41
Side effects of loop diuretics
- Hypovolemia - Hyponatraemia (decreased blood Na+) - Hypokaemia (decreased blood K+) - Hypomagnasemia - Hypocalcae,is - Metabolic alkalosis - Postural hypotension
42
What can be done to reduce the side effect of hypokalemia with loop diuretics
Dietary K supplementation or K sparing diuretics should be used to avoid hypokalemia
43
How so thiazide and thiazide like diuretics work
Stop the Na+ Cl- transporter Helps reabsorb calcium
44
Uses of thiazide and thiazide like diuretics
1st line antihypertensive (Bendroflumethiazide, Indapamide) Used for treatment of : - Essential hypertension - Mild heart failure - Calcimu nephrolithiasis due to hypercalciuria - Osteoporosis - Nephrogenic diabetes insipidus polyuria
45
Excretion and absorption affected by thiazide
Increase urinary excretion of: NaCl, K, Mg Increase absorption of: calcium Decrease excretion of: Uric acid, urinary calcium
46
What usually happens with aldosterone at the collecting duct
Binds to receptor Causes increased expression of ENAC and ROMK Get more reabsorption of sodium, greater loss of potassium
47
What do potassium sparing diuretics do and where do they work
Block the potassium channels so inhibits ROMK Late DCT/CD
48
What do aldosterone antagonists do and where do they work
Stop aldosterone being released, reduces ENAC Late DCT/CD
49
Why might you give loop diuretic at the same time as potassium sparing/aldosterone antagonist
Ensure not too much Potassium is lost
50
Example of potassium sparing
Amiloride
51
Example of aldosterone antagonists
Spironolactone
52
What do potassium sparing and aldosterone antagonist diuretics do
Increase urinary sodium excretion Decrease urinary potassium excretion Decrease H+ excretion
53
Uses of potassium sparing and aldosterone antagonists
Secondary hyperaldosteronism CHF, hepatic cirrhosis, nephrotic syndrome Treatment of hypertension (combined with thiazide or loop diuretics to correct for hypokalemia)
54
Potassium sparing and aldosterone antagonists are contraindicated in
Hyperkalaemia (as in chronic renal failure, K+ supplementation, Beta blockers or ACE inhibitors needed) Liver disease (dose adjustment needed)

Urinary (20 decks)

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