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Metabolism CC > Renal Excretory Function > Flashcards

Renal Excretory Function Flashcards

1
Q

Glomerular filtration

A

180L of plasma filtered every day

1-2L urine produced

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2
Q

Factors that determine filtrate

A 
Net filtration pressure
Podocyte slit pores
Size of molecule
Charge of molecule
--> -ve charge of GBM glycoproteins
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3
Q

Filtration at Glomerulus

A 
Free movement of small solutes/molecules
--> water, electrolytes (Na, K, Cl, phosphate, glucose). urea, amino acids
Restriction of larger solutes/proteins 
--> MW cut off of 5200 daltons
--> MW of albumin is 69,000 daltons
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4
Q

GFR

A

Total amount of fluid that is filtered through the glomerulus of both kidneys
180L/day
120ml/min
Clearance of substance

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5
Q

Creatinine clearance

A

Breakdown product of creatine phosphate (found in muscle)
Freely filtered in glomerulus
Secreted by peritubular capillaries –> creatinine clearance overestimates actual GFR by 10-20%

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6
Q

Creatinine clearance formula

A

(Urine Cr conc x Urine vol per min)/ Plasma Cr conc

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7
Q

To measure clearance of substance, have to

A

Measure conc. of creatinine in plasma
Collect urine for fixed period to get urine flow (ml/min)
Measure conc. of creatinine in collected urine

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8
Q

GFR measurements all methods

A

Creatinine clearance –> 24hr urine collection
Nuclear medicine scan (gold standard)
Estimated GFR- MDRD equation

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9
Q

4 variables in MDRD equation

A

Creatinine
Age
Gender
Ethnicity

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10
Q

Creatinine GFR Muscular individuals

A

Creatinine produced by muscle –> muscular individuals have naturally raised serum creatinine
–> eGFR underestimates true GFR

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11
Q

Creatinine GFR Malnourished individuals

A

Low serum creatinine

eGFR over estimates true GFR

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12
Q

Trimethoprin

A

Inhibit tubular secretion of creatinine

–> raised plasma creatinine even though GFR may be unchanged

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13
Q

Tight junction

A

Limits water + solute movement between cells

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14
Q

Secondary active transport

A

Use energy from non-ATP sources i.e. electrochemical gradients

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15
Q

Maintenance of interstitial Na conc

A

Use of active transportation

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16
Q

Primary active transport

A

Use ATP as energy source to drive movement

e.g. Na/K ATPase

17
Q

Cystinuria

A

Autosomal recessive
Proximal tubule
Apical Na/cystine cotransporter
Abnormal cystine excretion

18
Q

Renal glycosuria

A

Proximal tubule
Apical Na/glucose cotransporter
Abnormal urinary glucose loss
Happens despite normal/low blood flow

19
Q

Proximal RTA

A

Proximal tubule
Basolateral Na/HCO3 cotr.
Type 2 renal tubular acidosis

20
Q

Bartter type 1

A

Thick ascending loop of Henle
Apical Na/K/2Cl co transporter
Mimic effects of furosemide
–> hypokalaemia, metabolic alkalosis, hypocalcaemia, hypomagnasaemia

21
Q

Gitelman’s

A

Distal tubule
Apical Na-Cl cotransporter
Mimic thiazide use
–> hypokalaemia, metabolic alkalosis, hypomagnesaemia, hypercalcaemia

22
Q

Proximal tubule anatomy

A

Apical brush border (microvilli), large SA
1st 2/3- proximal convoluted tubule
Final 3rd- proximal straight tubule

23
Q

Proximal tubule function

A

Bulk of reabsorption of solutes- up to 80%
Water- up to 65%
Amino acids, low molecular weight proteins- up to 100%

24
Q

Loop of Henle aim

A

Reduce volume of water + solutes within urine but without changing concentration
–> creates hypertonic medulla

25
Q

Thick ascending loop of Henle

A

Active transport sodium
Impermeable to water
–> water reabsorption from descending loop to reach osmotic equilibrium

26
Q

Difference in osmolality in ascending + descending loop

A

Around 200 mOsm

27
Q

Vasa recta

A

Maintains osmotic gradient by counter-current exchange

28
Q

Descending loop of henle

A

Water by osmosis

29
Q

Ascending loop of henle

A

Secondary active transport of Na, K and Cl in thick ascending limb
Paracellular transport of Na, Ca and Mg down an electrochemical gradient

30
Q

Loop diuretics

A

Inhibit Na K Cl secondary transporter in thick ascending limb

31
Q

Distal nephron consists of

A

Distal tubule
Connecting tubule
Collecting duct (cortical + medullary)

32
Q

Distal nephron function

A

K excretion
Regulation Na delivery to collecting duct
Urine acidification

33
Q

ADH

A

Collecting tubule
Aquaporins become permeable to water
Water –> interstitium down conc. gradient
Conc. urine

34
Q

Renal threshold

A

Concentration of a substance dissolved in the blood above which the kidneys begin to remove it into the urine
–> when reached, kidney stops reabsorbing it

35
Q

Normal plasma 5mmol/L glucose

A

All filtered glucose reabsorbed

none excreted

36
Q

Plasma glucose 10mmol/L

A

glucose appears in urine (glycosuria)

Metabolism CC (29 decks)

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