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CPR Final Exam > Renal Physiology > Flashcards

Renal Physiology Flashcards

1
Q

What makes up the glomerular fiiltration barrier?

A
  • Capillary endothelium
  • Glomerular basement membrane
  • Podocyte epithelium
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2
Q

what size particles will get filtered?

A
  • smaller than 20 A get freely filtered
  • those greater than 42 A are not filtered
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3
Q

What are the lamina rara interna and externa composed of? What is the significance?

A
  • Proteoglycans
    • predominately heparin sulfate
  • These provide a negative charge to the GBM
    • important because it will repel other negatively charged molecules such as proteins
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4
Q

What happens if the negative charge of the GBM is removed?

A
  • There will be an increase in filtration of anions
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5
Q

What are the three layers to the GBM?

A
  • Lamina rara externa
  • Lamina densa
  • Lamina rara interna
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6
Q

What does the glycocalyx form and whats the significance?

A
  • Forms a sticky biogel in the endothelial lumen of the glomerular capillary
  • In order for molecules to be filtered they also have to pass through the glycocalyx
    • it contributes to the size and charge filterability
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7
Q

Examples of freely filtered molecules?

A
  • Water
  • Glucose
  • AA
  • Electrolytes
  • concentrations equal on both side of the membrane
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8
Q

How do you calculate urinary excetion?

A
  • Amount filtered - reabsorbed + secreted
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9
Q

How do you calculate tubular reabsorption?

A
  • Glomerular filtartion - urinary excretion + amount secreted
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10
Q

If excretion is greater than filtration, what happened?

A
  • Tubular secretion
  • substances moving from the peritubular capililaries into the renal tubular lumen
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11
Q

What is urine excretion rate?

A
  • Urinary concentration (Ux) of X which is sthe [] of the substance in urine in a given volume
    • Ux= concentration/volume
  • Urine flow rate (V) is the rate at which urine is produdced, depends on fluid intake and homeostasis
    • normally if fluid intake is increased the flow will increase
    • V= urinve volume/time
  • Urine excretion rate= Ux X V
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12
Q

What does renal clearance mean

A
  • Rate at which subtance is removed from the kidneys
  • Volume of plasma completely cleared of a substance by the kidneys per unit time

Ratio of urinary excetion to plasma volume

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13
Q

Calculate renal clearance of urea.

  • Purea = 20 mM
  • Uurea= 400 mM
  • V= 1.44 L/day (1mL/min)
A
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14
Q

If substance is present in blood at a concentration of 1 mg/mL and in urine at 100 mg/mL and the urine flow rate is 1 mL/min what will the renal clearance be?

A
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15
Q

What is the GFR?

A

Volume of plasma filtered into the nephron of both kidneys at the same time

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16
Q

What should the GFR be on average?

A
  • 125 mL/min (180 L/day)
  • Filtration fraction is 20% of Renal blood flow
17
Q
  • FF=20% RPF
  • GFR=125 mL/min
  • what is RBF in mL/min?
A

FF=GFR/RBF

  • 125mL/min/(0.20)= 625 mL/min
18
Q

What is filtration fraction?

A
  • Fraction of RBF (RPF) that is filtered across the glomerulus
  • Influenced by BP and ultrafiltration pressure
  • FF=GFR/(RBF)
19
Q

What happens to oncotic pressure as FF increases?

A
  • Oncotic pressure of the efferent arteriole increaes to facilitate reabsoprtion of tubular fluid
20
Q

How do you calculate filtered load of X?

A
  • GFR x Px

P is the plasma concentration

21
Q

What percentage of the filtered load of sodium is reabsorbed per day?

  • PNa=140 mEq/L
  • GFR=180L/day
A
22
Q

When will GFR be directly proportional to renal clearance?

A
  • Substance has to be freely filterable in glomeruli
  • Substance cant be reabsorbed or secreted by renal tubule
  • Substance can’t be synthesized, broken down or accumulated by kidney
  • Substance must be inert and non toxic w/o effect on renal function
23
Q

What substance meets the four standards for using renal clearance to estimate GFR?

A
  • Inulin
  • Creatinine
24
Q

Effects of systemic sympathetic stimulation?

A

Local renal sympathetic nerves get activated which

  • constricts renal arterioles to decrease GFR
  • Increase tubular reabsorption of water and salt
  • Activates RAAS which further increases tubular reabsorption
25
Q

What is PGC?

A

Pressure within glomerular capillary pushing out

26
Q

PBC?

A

Hydrostatic pressure within bowmans capsule pushing in

27
Q

πGC ?

A
  • Oncotic pressure within glomerular capillary pulling in
28
Q

πBC?

A
  • Oncotic pressure within bowmans capsule pulling out
  • should be zero bc no proteins in capsule
29
Q
A
30
Q

What three physical factors contribute to GFR?

A
  • Hydraulic conductivity (permeabilty of fenestrated endothelium) Lp
  • Surface area Sf
  • Capillary ultrafiltration pressure PUF
31
Q

What is the ultrafiltration coefficient? Kf

A
  • Hydraulic conductivity Lp x surface area Sf= Kf
  • GFR= Kf x PUF*
32
Q

What can alter PUF?

A
  • Changing glomerular capillary pressure PGC
    • ​PGC determined by renal arterial BP
    • Afferent arteriole resistance
    • Efferent arteriole resistance
  • PUF= PGC-PBC-πGC
33
Q

How do you change ultrafiltration coefficient Kf?

A
  • Changing surface area and permeability as Kf was hydraulic conductivity X surface area
34
Q

What role do glomerular mesangial cells play?

A

Influence Sf

CPR Final Exam (16 decks)

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