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Renal > Kidney Processes > Flashcards

Kidney Processes Flashcards

1
Q

what is the hydrostatic pressure in the glomeruli?

A

50mmHg

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2
Q

what is the oncotic pressure difference between the bowman’s capsule filtrate and the glomerulus?

A

25mmHg

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3
Q

what is the net perfusion pressure in the kidney?

A

the difference between the hydrostatic pressure in the glomerulus (pressure favouring filtration) and the hydrostatic pressure of the bowman’s space and oncotic pressure of glomerulus (forces favouring reabsorption)
in other words the net pressure trying to push fluid out

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4
Q

why does oncotic pressure of glomerulus increase throughout filtration?

A

As more water leaves the glomerulus the protein conc is increasing

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5
Q

where does the blood in the efferent arteriole go?

A

leaves the glomerulus, it enters a portal vein and travels to a second capillary bed surrounding the Loop of Henle; (vasa recta ) here, the hydrostatic pressure is much more similar to a systemic capillary, while the osmotic (oncotic) pressure is much higher

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6
Q

what are the 3 layers between the glomerulus and the bowman’s space?

A

endothelial cells (with fenestrations)
negatively charged glycocalyx
Basement membrane containing thick negatively charged proteins such as collagen
podocytes

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7
Q

what is the main form of solute movement into the bowman’s capsule?

A

Bulk flow
(solvent drag occurs as filtrate is forced out)

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8
Q

what is the GFR?

A

120ml/min

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9
Q

what is the renal plasma flow rate?

A

600ml/min

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10
Q

what are the 2 main mechanisms of increasing glomerular GFR?

A

dilate afferent arteriole
contract efferent arteriole

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11
Q

what is proteinuria and what does it suggest?

A

protein in the urine suggests glomerular nephritis (dysfunction in the glomerulus) and or nephrotic syndrome (severe renal failure)

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12
Q

what is the classification of epithelial cells of the PCT?

A

simple columnar epithelium, with microvilli (to aid absorption)

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13
Q

what is the basolateral and apical surface in the PCT?

A

Apical side = filtrate side
Basolateral = interstitial space

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14
Q

how is water transported in the PCT?

A

paracellularly, through aquaporin 1 channels
drawn by oncotic pressure into interstitial space

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15
Q

how is glucose reabsorbed in the PCT?

A

Under normal conditions when glucose conc in the filtrate is high glucose is reabsorbed by SGTL2 which is a Na+ glucose symporter
High affinity / low capacity
further down the tubule when glucose conc is lower SGTL1 transports the glucose but it requires 2Na+ to do this as its moving against a large conc gradient. Low affinity / high capacity

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16
Q

what is the value for glucose Tm and why is it useful?

A

380mg/min-1
tubular maximum - max amount of glucose that can be reabsorbed, prevents excess glucose entering the blood by stopping too much being reabsorbed

17
Q

how does canagliflozin act and what are it side effects?

A

inhibits SGTL2 transporter, decreases glucose reabsorption
used to treat diabetes mellitus
increase glucose in urine = increase risk of UTI because glucose is available as a bacteria metabolite

18
Q

how are amino acids reabsorbed?

A

through various cotransporters, a lot of which use Na+

19
Q

how is Cl reabsorbed in the PCT?

A

anion exchanger (antiporter)
example is methanoic acid (charged form enters filtrate in exchange for Cl, combines with H+, so it now lipid soluble, renters the epithelial cell to redo process)
also via the paracellular route (solvent drag and passive diffusion, mainly occurs further down as water is lost and delivered to interstitial space so conc gradient is set up)

20
Q

explain how organic ions such as penicillin are secreted into the urine

A

Organic ion transporters present on the basolateral membrane transport the organic ions into the cell

Multidrug resistance associated protein transport inorganic ions from the cells into the filtrate in exchange for another anion e.g. Cl, HCO3 (antiporter system)
Organic ions compete with each other for excretion at both transporters

21
Q

explain the transporters / properties of epithelial cells on the thick Ascending limb

A

Uses NA/2CL/K cotransporter to move ions out of the filtrate (NKCC2 transporter)
there is K+ leak channels present on the apical side because there is a limited amount of K
multiple active ion transporters on the basal lateral side
lots of tight junctions to prevent paracellular movement of water etc

22
Q

how does water mainly leave the descending limb?

A

paracellular route

23
Q

what is the action of
Furosemide

A

acts on thick ascending limb
Blocks the NKCC2 cotransporter = less being pumped into interstitial space causing enormous diuresis and natriuresis

24
Q

what is furosemide used to treat?

A

hypertension, so used to treat cardiac and renal failure/ dysfunction

25
Q

what are the side effects of furosemide?

A

dehydration, excess K+ loss (hypokalaemia)
can result in cardiac arrythmias especially when applied with digoxin

26
Q

how is water reabsorbed in the collecting ducts?

A

paracellularly and through AQP2 (apical) then AQP3 (basolateral)

27
Q

what effect does aldosterone have on the collecting ducts?

A

stimulates increase synthesis of sodium potassium and NA/K ATPases in the collecting duct
This increases sodium and water reabsorption

28
Q

what effect does spironolactone have why is it used?

A

Spironolactone blocks the effects of aldosterone and therefore acts as a diuretic

It has used In heart failure as it’s a K+ sparing diuretic

29
Q

what is Urea Counter current Multiplication and how is it useful?

A

Urea transported out of the collecting ducts
increases the osmolarity of the medullary interstitial space to aid water reabsorption
then reabsorbed again in the loop of hele

30
Q

How is H+ secreted into urine?

A

Na+/H+ antiporter
(formed from carbonic anhydrase)

31
Q

how is HCO3 absorbed in the PCT?

A

forms CO2 in filtrate, diffuse into cell, forms HCO3 via CA then Na+ HCO3 symporter back

32
Q

what diuretic targets CA?

A

acetazolamide blocks carbonic anhydrase meaning no H+ is generated to travels into the filtrate, decreasing HCO3 absorption

33
Q
A

Renal (4 decks)

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