Renal Function - Pierce Flashcards
3 layers of the glomerular filtration barrier from capillary to bowmans capsule
- capillary endothelium (with glycocalyx -> sticks to - charge)
- Glomerular BM (3 layers to in, - charge proteoglycans)
- Podocyte epithelium (small pores up to 42Å)
layers of the Glomerular BM
- Lamina Rara Externa : proteoglycans - charge (NO PROTIEN)
- Lamina densa
- Lamina Rara Interna : proteoglycans - charge (NO PROTIEN)
what type of molecules get filtered though the glomerular barrier
HIGH : cations
medium or normal : neutral
LOW : Anions
Nephrotoxic Serum Nephritis
Disrupted Glycocalyx
= proteins can get through the barrier
= proteinuria
freely filtered molecules
water
small (glucose, aa, electrolytes)
what is not filtered
CELLS (RBC, WBC)
PROTIENS (large)
urinary excretion is what
Filtered + secreted - reabsorbed
what does Arterial input equal
Venous output + Urine output
Renal Clearance rate (Cx) is calculated how
Cx = (Ux)(V) / (Px) * accounts for substance in plasma and the urine V = urine flow rate Ux = concentration in urine
Urine Excretion Rate is calculated how
(Ux)(V)
V = urine flow rate
Ux = concentration in urine
how much does the glomerulus usually filter (GFR) in %
20% of the RBF
what is the normal GFR amount in ml/min
125ml/min
average amount reabsorbed from the filtrate
99%
FF (filtration fraction is calculated how)
FF = GFR/RBF
normal RBF is 625ml/min
what increases FF and what is the consequence
BP
increases FF = more proteins left behind = more capillary oncotic P = more reabsoption
as GFR increases
capillary oncotic P increases and reabsorption increases
Filtered load is what and how is it calculated
amount of a substance is filtered as a rate (mg/min)
= GFR x Pna
Filtered fraction is what
a percent of filtrate based on the whole (RBF)
when does Cx = GFR
renal clearance = GFR when substance calculated for is freely filtered
no reabsorption, no secretion, to toxin, not broken down in kidney
2 substances that filter freely
INULIN
Cr
how to use creatine to get GFR
measure plasma Cr level for 24hrs (Px)
measure urine Cr level for 24hrs (Ux)
measure amount peed for that time (V)
sympathetic effect on kidneys
a1 : constriction on afferent arterioles (and a little but for efferent)
+ increase tubular reabsorption or H2O and Na (proximal tubule epithelial cells have NA-ATPase)
B1 : activates Renin release to increase H2O and Na reabsorption (JG cells)
normal Bowman’s capsule oncotic P
0mmHg because there is no proteins in filtrate (piBC)
what P is the higherst
Glomerular capillary Hydrostatic P (Pgc)
what are 2 factors that change GFR
- permeability or leakiness of capillary (Lp)
- Total Hydrostatic P + Oncotic P in G capillary and BC (Puf)
- SA around glomerulus for filtration (Sf)
what does Kf mean
ultrafiltration coefficient
Sf x Lf
GFR calculation if you know Kf
GFR = Kf x Puf
major factor changing Puf
Pgc (due to BP, or resistance in the efferent or afferent arteriole)
what changes Kf
SA* for filtration is changes by Glomerular MESANGIAL cells that contract the endothelium
biggest drop in Hydrostatic P in arterial flow
how is the P in Gc
in Afferent arteriole and Efferent arteriole
Glomerular capillary is stable and high Hydrostatic P for being a capillary
2 things causing increased GFR
effect on RBF
- CONSTRICT Efferent (lower RBF)
2. DILATE Afferent (higher RBF)
2 things causing decreased GFR
effect on RBF
- CONSTRICT Afferent (lower RBF)
2. DILATE Efferent (higher RBF)
sympathetic stimulation causes what
(a1)
(B1)
- during low BP**
(a1) constriction of AFFERENT arteriole = lower GFR and lower RBF = bring GFR back down to normal
(B1) release Renin = increase BP
ACE inhibitor act where
EFFERNT ARTERIOLE —-I Angiotensin 2 = lowers GFR
where does Angiotensin 2 act
EFFERENT ARTERIOLES to increase GFR
constricting it (bring it back to normal)
+
increase Na H2O reabsorption = increase BP
where does sympathetic innervation act on most
AFFERENT ARTERIOLE to decrease GFR = less filtered = increase BP
+
releases some Renin = increase BP
vasoconstrictors
Sympathetic (a)
ATP, adenosine
Angiotensin 2 (e)
endothelin
vasodilators
Prostaglandins Bradykinin NO Dopamine ANP ACE-inhibitor (angiotensin 2)
increase GFR does what to PCT
increase REABSORPTION at PCT beacuse:
- increased oncotic P in capillary
- increased stuff in the urine (diffusion)
- increases stretch and shear of apical microvilli = Na-ATPase is placed to reabsorb NA
Autoregulation of BP 2 ways
- Local reflex
2. Physiological feedback ( Tubuloglomerular feedback)
Local feedback
*FAST REFLEX**** 1-2 sec from myogenic cells feedback during high BP : Dilate Efferent arteriole Constrict Afferent Arteriole
Tubuloglomerular Feedback
during high NA+
JG apparatus gets signal from
- Macula Densa (when Na is high in urine)
- JG cells cause NO Renin release
- lower reabsorption on NA into blood lower BP
- vasoconstrict AFFARENT arteriol
- lower GFR and RBF back to normal
Tubuloglomerular Feedback
during low NA+
- macular densa senses low NA (from low BP)
- JG cells release renin = increase BP
- affarent arteriole vasodilation (increase GFR and RBF back to normal)
Macula densa senses high NA
what are the biochemical steps to cause the results from this
- Macula densa cells reabsorb NA by (NKCC2 channel)
*NKCC2 takes in Na, 2Cl, K to MD - this causes MD to make ATP + adenosine
- MD releases this to basal side facing BVs SM (afferent)
- ATP –> P2X , Adenosine –> A1 on SM
- this causes CA release into the BV SM (afferent)
- VASOCONTRICTION of afferent arteriole
= lower GFR lower RBF back to normal
Macula densa senses low NA
what are the biochemical steps to cause the results from this
- Macula densa cells X NA by (NKCC2 channel)
*NKCC2 takes in Na, 2Cl, K to MD - this causes MD to X make ATP + adenosine
- MD releases X ATP or adenosine to BVs SM (afferent)
- X CA release into the BV SM (afferent)
- VASODILATION of afferent arteriole
= higher GFR higher RBF back to normal
2 things causing renin to be secreted
- low NAcl to MD
2. B1 to JG cells
MC also activates JG cells and causes what
during low NA
vasoconstriction of EFFERENT arteriole
+ vasodilation of afferent on its own
LOW BP causes what in SYMPA and MD direct and indirect **
SYMPA : directly by a1 = constrict AFFERENT (iBP)
MD DIRECT : no CA = dilate AFFERENT (iGFR)
MD INDIRECT : activate JG cells to release renin, angiotensin 2 = constrict EFFERENT (iGFR)
reason angiotensin 2 causes vasoconstriction of the efferent arteriole during low BP
to increase GFR
to increase amount filtered
so that aldosterone can do its job and reabsorb a lot from the urine while also restoring low GFR
ADH and ANP during low NA or low BP
increase PP stimulation to secrete ADH
inhibit Atrial myocytes from secreting ANP
= reabsorb NA = increase BP
3 things that care about keeping GFR right
INTRINSIC
- autoregulation local reflex
- Tubuloglomerular feedback (MD)
- Angiotensin 2
4 things that care about keeping BP right
EXTRINSIC
- Sympathetic
- Angiotensin 2
- Renin + ADH + other hormones
- Blood comosition
FE
Fractional Excretion 1.0 : F GFR = E 0.9 : less excreted then filtered GFR 1.1 : more excreted then filtered GFR FE= (Ux)(Pcr) / (Px)(Ucr)
