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46 Cards in this Set
- Front
- Back
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[ juxtamedullary / superficial ] nephrons have their glomeruli in the cortex ; [ juxtamedullary / superficial ] nephrons have their glomeruli near the junction of the cortex and medulla.
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superficial - cortex ; juxtamedullary - juntion of cortex and medulla
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The juxtaglomerular apparatus is a specialized region with three major components. Name em.
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1. juxtaglomerular cells - surround the afferent arterioles and secrete renin.
2) macula densa - specialized region of the early distal tubule that comes into close contact with its own glomerulus 3) mesangial cells - line the glomerulus, and afferent and efferent arterioles |
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What are the two important functions of the juxtaglomerular apparatus?
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1) secretion of renin by juxtaglomerular cells
2) tubuloglomerular feedback |
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Put the following components of blood supply in the order of directional blood flow:
A. afferent arterioles B. efferent arterioles C. glomerular capillaries D. peritubular capillaries E. progressively smaller arteries F. renal artery G. renal vein H. small veins |
F. renal artery
E. progressively smaller arteries A. afferent arterioles C. glomerular capillaries B. efferent arterioles D. peritubular capillaries H. small veins G. renal vein |
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Basics of urine production:
Glomerular filtration of ______L/day produces ultrafiltrate of plasma. Modification of this filtrate by reabsorption and secretioni produces the final urine of _____ L / day. |
180 L / day ; 1-1.5 L /day
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What is the equation for measurement of renal clearance?
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clearance of substance x = (urinary concentration of substance x)*(urine flow rate) / (plasma concentration of substance
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True or False:
Clearance of x is the volume of plasma cleared of substance x per unit time. |
True
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Substances with highest clearances are
A. filtered and reabsorbed B. filtered and secreted |
B. filtered and secreted
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Substances with the lowest clearances are
A. filtered and reabsorbed B. filtered and secreted |
A. filtered and reabsorbed
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Substances that are filtered only (such as _____) are glomerular markers and have a clearance equal to the glomerular filtration rate.
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inulin
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What is the equation for clearance ratio?
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clearance ratio = (clearance of substance x) / (clearance of inulin)
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A clearance ratio of 1.0 means...
A. that substance X is also a glomerular marker B. the substance is either not freely filtered or is filtered and subsequently reabsorbed C. the substance is both filtered and secreted |
A. that substance X is also a glomerular marker
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A clearance ratio of < 1.0 means...A. that substance X is also a glomerular marker
B. the substance is either not freely filtered or is filtered and subsequently reabsorbed C. the substance is both filtered and secreted |
B. the substance is either not freely filtered or is filtered and subsequently reabsorbed
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A clearance ratio of > 1.0 means....
A clearance ratio of < 1.0 means...A. that substance X is also a glomerular marker B. the substance is either not freely filtered or is filtered and subsequently reabsorbed C. the substance is both filtered and secreted |
C. the substance is both filtered and secreted
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Renal blood flow (and GFR) are kept constant over a wide range of arterial pressures by changing the resistance of the afferent arterioles, a phenomenon called __________.
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autoregulatioin
p. 520 |
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Two mechanisms explain autoregulation:
1. myogenic hypothesis 2. tubuloglomerular feedback Detail em. |
1. myoggenic hypothesis: like in cardiovascular physiology. When arterioles are stretched, the contract and lead to increased resistance. In kidneys, the afferent arterioles contract.
2. Tubuloglomerular feedback - when arterial pressure increases, both RBF and GFR transiently increase leading to increased delivery of solutes and water to the macula densa of distal tubule. Macula densa senses increased load and secretes vasoactive ADENOSINE that causes local constriction of nearby afferent arterioles. p. 520 |
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Describe the tubuloglomerular feedback mechanism that explains autoregulationin the kidneys.
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Tubuloglomerular feedback - when arterial pressure increases, both RBF and GFR transiently increase leading to increased delivery of solutes and water to the macula densa of distal tubule. Macula densa senses increased load and secretes vasoactive ADENOSINE that causes local constriction of nearby afferent arterioles. p. 520
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Why is the macula densa important and what does it secrete?
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Tubuloglomerular feedback - when arterial pressure increases, both RBF and GFR transiently increase leading to increased delivery of solutes and water to the macula densa of distal tubule. Macula densa senses increased load and secretes vasoactive ADENOSINE that causes local constriction of nearby afferent arterioles. p. 520
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What substance is used to measure renal plasma flow (RPF)?
A. adenosine B. inulin C. PAH D. radioactive phosphorus |
C. PAH, or para-aminohippuric acid
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True or False:
PAH his both filtered and secreted by the kidney thus it has a very high renal clearance and is a good marker to measure renal plasma flow. |
True
p. 522 |
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What is the effective Renal Plasma Flow equation?
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effective renal plasma flow equation = ([PAH] in urine * urine flow rate) / ( [PAH] in venous plasma)
note: this is also the clearance of PAH. p. 523 |
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What is the true Renal Plasma Flow equation?
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True RPF = ( [PAH] in urine * urine flow rate ) / ( [PAH] in renal artery - [PAH] in renal vein)
p. 523 |
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What is the renal blood flow equation?
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RBF = RPF / (1-Hct)
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Why do we care about RPF and RBF? (Why do we want to know RPF?)
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RPF can be measured directly with PAH. PAH is dissolved in plasma, not in RBCs. So , we measure RPF with PAH, and we calculate RBF from RPF, by knowing the Hct. p. 524
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Seiving coefficient of 1.0 means...
A. the substance is freely filtered B. the substance is restricted C. the substance is hyperfiltered |
A. the substance is freely filtered
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The lower the seiving coefficient, the
A. the more the substance is freely filtered B. the more the substance is restricted from filtering C. the more the substance is hyperfiltered |
B. the more the substance is restricted from filtering
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What three things listed on the sieving coefficient table have sieving coefficients < 1.0?
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Myoglobin (0.75)
Hemoglobin (0.03) Serum albumin (<0.01) |
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Which has the lowest sieving coefficient?
A. Cl- B. Hemoglobin C. Inulin D. Myoglobin E. Serum albumin |
E. Serum albumin! ( <0.01)
A. Cl- = 1.0 B. Hemoglobin = 0.03 C. Inulin = 1.0 D. Myoglobin = 0.75 |
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What are the two factors that determine filterability?
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Molecular weight and charge (negative charges are repelled by the already negatively charged glomerular barrier)
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Starling forces determine GFR. What is the equation for Starling forces in the kidney?
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GFR = K * [ (Pgc-Pbs) - glomerular capillary colloidosmotic pressure ]
p. 526 |
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What are the three Starling forces at work across the glomerular capillary that determine GFR? For each, does it favor or oppose filtration?
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- Pgc, or pressure from the glomerular capillary (favors filtration, pushes out of glomerular capillary into Bowman's space)
- Pbs, or pressure from Bowman's space (opposes filtration, pushes from Bowman's space to glomerular capillary) - oncotic pressure from glomerular capillary (opposes filtration, pulls towards itself in the glomerular capillary) |
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Of the three Starling forces of the kidney, which is usually the only one that changes?
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The three Starling forces are:
Pgc (pressure from glomerular capillary), Pbs (pressure from Bowman's space), Oncotic pressure from glomerular capillary. The only one that usually changes is the Oncotic pressure from glomerular capillary. It becomes stronger as it moves towards the efferent end of the capillary. p. 527 |
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Regarding Starling force changes, why doesn't Pgc fall?
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Pressure in the glomerular capillary does NOT fall because the efferent end is narrower so the pressure is maintained. p. 527
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What is the filtration fraction equation?
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GFR / RPF
p. 528 |
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What is the effect of the following scenarios on RPF, GFR and filtration fraction?
A. constriction of afferent arteries B. increased [plasma protein] |
A. constriction of afferent arteries:
decrease RPF, GFR. No change to filtration fraction (since both is decreased) B. increased [plasma protein]: no change to RPF, decrease in GFR (b/c higher osmotic pressure in glomerular capillary), lower filtration fraction overall |
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What is the effect of the following scenarios on RPF, GFR and filtration fraction?
A. constriction of ureter B. Antiogensin-II constriction of efferent arterioles |
A. constriction of ureter:
no change to RPF, decreased GFR (b/c increased Pressure from Bowman's Space), thus decreased filtration fraction B. Antiogensin-II constriction of efferent arterioles: decreased renal plasma flow, increased GFR (due to increased glomerular capillary pressure), increased filt frac. |
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What does activation of the sympathetic nervous system (alpha1 receptors) do to the renal arterioles?
A. constrict afferent arterioles B. constrict efferent arterioles C. dilates afferent arterioles D. dilates efferent arterioles |
A. constrict afferent arterioles
Thus, decrease RBF and GFR. No change to filtration fraction. p. 530 |
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What does Angiotensin II do to the renal arterioles?
A. constrict afferent arterioles B. constrict efferent arterioles C. dilates afferent arterioles D. dilates efferent arterioles |
B. constrict efferent arterioles
Thus, increase GFR (since increase in Pgc) and decrease in RPF. |
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What does an ACE inhibitor do to the renal arterioles?
A. constrict afferent arterioles B. constrict efferent arterioles C. dilates afferent arterioles D. dilates efferent arterioles |
D. dilates efferent arterioles
Thus decreases GFR (since Pgc), increases RPF (b/c more flow). |
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What does ANP do to the renal arterioles?
A. constrict afferent arterioles B. constrict efferent arterioles C. dilates afferent arterioles D. dilates efferent arterioles |
both B. constrict efferent arterioles
C. dilates afferent arterioles Thus signif increases GFR (since signif increase Pgc) and increases RPF (b/c more flow). |
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What does a locally secreted renal prostaglandin do to the renal arterioles?
A. constrict afferent arterioles B. constrict efferent arterioles C. dilates afferent arterioles D. dilates efferent arterioles |
C. dilates afferent arterioles
(local renal prostaglandins are secreted in high vasoconstrictor states) Thus, increases GFR and RPF. |
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True or False:
Low dose dopamine to person with a lot of blood loss does the same thing to the renal arterioles as local renal prostaglandins - dilates efferent arterioles. |
FALSE. They do the same thing, yes but that same thing is dilate AFFERENT arterioles, thus increasing GFR and RPF.
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True or False:
Inulin is a glomerular marker, and its clearance measures GFR. |
True
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True or False:
Inulin is not an endogenous substance, thus it must be administered to measure RPF. |
FALSE. Inulin is not endogenous but it is used to measure GFR. PAH is used to measure RPF!
Creatinine IS endogenous and it is a near-perfect glomerular marker so usually creatinine clearance can also be used to measure GFR. |
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Why is the clearance of PAH the effective RPF while the clearance of inulin is the GFR?
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PAH and inulin are both filtered but only PAH can additionally be secreted- inulin cannot.p. 531
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What is the filtration fraction equation and what is it's usual value?
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Filtration fraction = GFR/ RPF
its value is usually 0.2, or 20%, meaning that 20% of the renal plasma flow is filtered across the glomerular capillaries. The remaining 80% leaves by the efferent arterioles and becomes the peritubular capillary blood flow. p. 532 |
