Renal Flashcards
What percentage of the TBW does interstitial fluid occupy?
Interstitial fluid:3/4 of ECF
ECF:1/3 of TBW
>interstitial fluid :3/12 TBW
It is an ultrafiltrate of plasma
What percentage of the TBW does plasma occupy?
Plasma is 1/4 of the ECF
ECF is the1/3 of the TBW
>plasma:1/12 TBW
It consists of albumin,globulins,Na,Cl,HCO3-
How can we measure TBW?
#tritiated water #D2O #antupyrene
How can we measure ECF?
#sulfate #inulin #mannitol
How can we measure plasma?
#radioiodinated serum albumin(RISA) #evans blue
How is plasma osmolarity measured?
Posm=2Na+glucose/18+BUN/2,8
How much is the osmolarity difference between ECF and ICF at a steady phase?
They are equal>water shifts between ECF and ICF
NaCl,mannitol:do not cross cell membranes >ECF!
What kind of changes in volume/osmolarity of blood fluids can cause no change in Hct?!
HYPERosmotic-CONtraction: sweating,fever,DM> [plasm.prot]^+H2O out of the RBC>unchanged Hct
"Opposite changes" #HYPOsmotic-EXPansion: SIADH>[plasma.pr.]low+H2O into the RBC>unchanged Hct
What kind of changes in volume/osmolarity of blood fluids do these changes cause?
- SIADH
- adrenal insufficiency
- diarrhea
- ^NaCl intake
- isotonic NaCl infusion
- DM
- Hyposmotic expansion
- Hyposmotic contraction
- isotonic contraction
- hyperosmotic expansion
- isotonic expansion
- Hyperosmotic contraction
What is the effect of prostaglandins E/I,bradykinin,NO,D in RBF?
They cause vasodilation of the renal arterioles >^RBF
How is the effective Renal Plasma Flow measured?
RPF=Upah*V/Ppah
PAH:filtered +secreted
This equation underestimates true RPF by 10%❗️
How is Renal Blood Flow RBF measured?
RBF=RPF/1-Hct
How is GFR measured?
GFR=Uinulin*V/Pinulin=Kf[(Pgc-Pbs)-(πgc-πbs)]
Inulin=FILTERED NOT SECRETED
How is filtration fracture estimated?
What effect does it have on the reabsorption in the proximal tubule!
Filtration fracture =GFR/RPF
Normally=0,2—>20%of RPF is filtered
#^FF=^[protein] of peri tubular capillary=^reabsorption in the proximal tubule. #low FF=low[protein] of the peritubular capillary=low reabsorption
What are the components of glomerular filtration barrier?
#fenestrated capillary endothelium>SIZE BARRIER #fused basement membrane>NEGTIVE CHARGE BARRIER:loss in the nephrotic syndrome! #epithelial layer>podocyte foot
What is the connection between a substance x and GFR ,as far as it’s clearance is concerned?
Cx>GFR=net tubular secretion of X
Cx<GFR=net tubular absorption
Cx=GFR=No secretion/no reabsorption.
How does Pgc change across the length of the capillary?
Pgc is CONSTANT across the length do the capillary
-^by the dilation of the afferent capillary or constriction of the efferent
How does πgc change along the length of the capillary?
Πgc increases across the length of the capillary>filtration of H2O>[protein]^
How does angII/sympathetic stimulation/prostaglandins affect FF?
- ang II=constriction of the efferent>^GFR,same RPF>^FF
- sympathetic=constriction of the afferent>low GFR,low RPF>same FF
- prostaglandins=dilation of the afferent>^GFR,^RPF>same FF
How can Pbs be increased?
By constriction of the ureters(stone)
What does juxtaglomerular apparatus consist of?
#mesangial cells #JG cells=modified smooth cells of the afferent arteriole)>renin #macula densa=NaCl sensor at the DCT>adenosine
How is filtered load/excretion rate/reabsorption/secretion estimated?
Filtered load=GFRP
Excretion rate=UV
Reabsorption=filtered-excreted
Secretion=excreted-filtered
How does filtered load affect reabsorption?
^filtered load>^reabsorption
At what point does the glucose reabsorption stop and we start seeing glucosuria..?under what condition is glucosuria considered “normal”?
(heterogeneity of nephrons)
Normal pregnancy may cause glucosuria+aminoaciduria
How is amino acids clearance determined?
They are ~100%reabsorbed in the PCT via Na-cotransport
What is the Hartnup disease?
ARecessive
Deficiency of neutral amino acids transporters>I.e. tryptophane> low niacin(B3)>pellagra-like symptoms=3D:Diarrhea,Dementia,Dermatitis
Before the Tm point,PAH clearance equals…?
Filtration+secretion~>RPF
Once the Tm for secretion is exceeded >all carriers are satires >flat excretion rate
What is the correct order of relative clearances of the several components of plasma?
PAH>K(in high diet)>inulin>urea>Na>glucose,amino acids,HCO3-
What alteration can we do to the urine pH in order to increase excretion of salicylic acid and morphine?
salicylic acid:weak acid>alkalization of the urine=^A->low reabsorption
What does TF/P ratio stands for?
TF/P=1
TF/P ratio=compares the concentration of a substance in tubular fluids with the concentration in plasma
-no reabsorption of the substance
-reabsorption was proportional to H2O reabsorption=ίδιες συγκεντρώσεις
#TF/P1
-H2Oreabsorption>reabsorption of the substance
-secretion of the substance
What is the TF/P ration for Cl in the PCT?
It is >1 because reabsorption of Cl is proportionally less than reabsorption of H2O=σταθερή γραμμή
What is the TF/P ration in the bowman space for any freely filtered substance?
It is 1
What is the TF/P ratio for inulin across the tubule length?
Inulin is filtered but neither reabsorbed nor secreted.thus,the m(inulin) I the TF Is fixed throughout the tubules.but,as we move toward the collecting duct H20reabsorption steadily increases>lower V left in the tubules>steady increase in the [inulin]tf>steady increase in the TF/p ratio
How can TF/P inulin be used to measure H20 reabsorption?
[inulin]tf is determined solely by how much water remains in the TF
Fraction of filtered H20reabsorbed=1-1/TF/Pinulin
What are the 7causes of shifting K outside of cell>^K+?
#Digitalis #hyperOsmolarity #Lysis(Ca,exercise) #Acidosis>counter transport of H/K #b-blockers #^blood Sugar
What are the 4 causes that shift K into cells?>Hypokalemia ?
#hyposmolarity #alkalosis #b-adrenergic agonist #insulin
What are the 6 causes of increased distal K secretion?
#Hyperaldosteronism #^K diet #alkalosis #thiazide diuretics #loop diuretics #luminal anions
What are the 4 causes of decreased distal K secretion?
#low K diet #low aldosterone #acidosis#K sparing diuretics
What kind of diuretics could be used to treat hypercalcemia?
Loop diuretics>block Na reabs>block Ca-Na cotransport
What kind of diuretics could be used to treat idiopathic hypercalciuria?
Thiazide diuretics>^Ca reabsorption>low Ca secretion>lower Ca in the urine
What part of the nephron is considered a concentrating segment?
Thin descending >impermeable to Na/passively reabsorbs H2O
What parts of the nephron are considered diluting?
Thick ascending>impermeable to H2O
DCT>cortical diluting segment>imper,enable to H2O
How is free water clearance estimated?
Ch2o=V-Cosm
➕:loss of H20 >low ADH>hyposmotic urine
#high H2O intake
#cental diabetes insipidus
#nephrogenic diabetes insipidus
➖:no loss of H2O>^ADH>hyposmotic urine
#SIADH
#water deprivation
0⃣:treatment with loop diuretics>no contraction/no dilution
What is the main difference between SIADH and water deprivation as far osmolarity is concered?
Water deprivation will have normal/high serum osmolarity
SIADH will have very low serum osmolarity due to the excess of H2O
Both pathologies have:
- ^ADH SERUM
- hyperosmotic urine
- low urine flow rate
- negative Ch2o
What are the factors that stimulate renin secretion?
#Low BP>JG cells #low Na >macula densa #^sympathetic tone(β1)
Where is ACE mostly produced?
In the lungs(+kidneys)
What are the 6 effects of ANGII ?
#action on the AT1receptors>vasoconstriction>BP
#constriction of the efferent>^GFR,low RPF>^FF
#^aldosterone>^ENaC>^reabsorption of Na in the principal cells
>^excretion of K in the principal cells
>^excretion of H in the a-intercalated cells
--->favorable gradient for reabsorption of Na and H2O
#^ADH>^V2(cAMP)>aquaporins>H2Oreabsorption
>^V1(IP3)>vasoconstriction
#^Na/H activity in PCT>^Na,HCO2,H2O reabsorption>contraction alkalosis
#hypothalamus>thirstVia what molecular do ANP,BNP act?
ANP(atria),BNP(Ventricles)>^cGMP>relax vascular smooth muscle>^GFR>renin
What effect do NSAIDs have on the GFR?
NSAIDs block renal protective prostaglandins synthesis>less vasodilations>^constriction of the afferent>low GFR>acute renal failure
What are the buffers for HCO3 reabsorption in the PCT?
How is it regulated?
Reabsorption of HCO3(production via carbonic anydrase)
Recycling of H+>conjunction with HCO3 in the lumen >CO2>diffusion back in the cell
Regulation:
#^filt.load>^reabsorption
#^Pco2>^reabsorption
#^ECF Volume>less reabsorption
^angII>^Na/H>^reabsorption:contraction alkalosis
H+ can be buffers through ti titriated acid and NH3.
H2PO4- buffering depends on what?
After HCO3- is reabsorbed ,H+ is secreted in the lumen via H/ATPase (^via aldosterone)>+HPO4->H2PO4->excreted
It depends on #the amount of urinary buffers(HPO4-) #pK of the buffer
H+ can be buffers through ti titriated acid and NH3.
NH3 buffering depends on what?
After HCO3- has been reabsorbed ,H+ is secreted in the lumen via H/ATPase(^via aldosterone)>+NH3>NH4+>excreted
NH3 is produced into the cells from glutamine>diffused in the lumen
Depends on: #low pH of the urine>^gradient for diffusion of NH3>^excretion #low pH of the plasma>^synthesis of NH3>^excretion #^K>less production of NH3>less excretion of H+>renal tubular acidosis 4
What are the causes of metabolic acidosis with ^anion gap?
MUDPILES: #methanol #uremia>renal failure #diabetic ketoacidosis #propylene glycol #iron tablets/isoniazid #lactic acidosis >shock #ethylene glycol #salicylates
What are the causes of metabolic acidosis with normal A-a gradient?
HARDASS #hyperalimentation #addison #renal tubular acidosis #diarrhea #acetazolamide #spironolactone #saline infusion
What other electrolyte disturbance can respiratory alkalosis cause?
Hypocalcemia.
Because H+ and Ca2+ compete for binding sites on plasma proteins>low H+>^Binding Ca2+>les ionized Ca2+
To maintain normal H+ balance !total daily excretion of H+ should equal the daily…..?
Fixed acid production plus fixed acid ingestion
Why is it not recommended for marathon athletes to drink distillates water?
When the athlete is sweating>more loss of H2O than salt>hyperosmotic volume contraction>h2O comes out of the ICF towards ECF>if he consume more H2O>even more Vecf>hyposmotic plasma
