DSA- Introduction to Renal Blood Flow and GFR Flashcards

1
Q

Describe 3-layered structure of the glomerular capillary filtration barrier

A

1) Capillary Endothelium
- Fenestrated
- permeable to water and small solutes in glomerulus
2) Glomerular Basement Membrane
- fibrous network of collagen, laminin, proteoglycan, glycoprotein
3) Podocyte Epithelium
- long, extending foot processes
- covered by a diaphragm
- form the walls of filtration slit

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2
Q

What is glycocalyx and what is the contribution to the barrier function of the endothelial surface layer?

A
  • Negative-charged biogel like surface structure of proteoglycans
  • glomerular endothelium
  • lines interior of capillary lumen
  • contains heparan sulfate and hyaluronan
  • controls transcapillary fluid exchange
  • biomechanical sensor
  • provide molecular filling to fenestrate
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3
Q

What can freely filter in filtration barrier?

A
  • water
  • small solutes (glucose, amino acids, electrolytes)
  • concentration equal on both sides of membrane
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4
Q

What can NOT freely filter in filtration barrier?

A
  • large molecules (proteins)
  • formed elements ( cells)
  • Tamm-Horsfall protein
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5
Q

What is a Tamm-Horsfall protein? Where is it produced? function?

A
  • glycoproteins not freely filtered in urine
  • produced by the thick ascending loop of Henle
  • prevent the crystallization of calcium in the nephron
  • prevent urinary tract infections.
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6
Q

Filtration slits (Components, location, size range for filtration)

A
  • Podocytes are held together by certain cell adhesion molecules.
  • Nephrin (in slit) is often damaged in certain kidney disease states. It can also be mutated in some diseases.
  • Molecules greater then 42 Å are not filtered
  • molecules less than 20 Å are freely filtered.
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7
Q

Filtered components depend on… (2)

what about biogel?

A

1) Size
- smaller-> more freely filtered
2) charge
- more positive ions-> more freely filtered

More freely cleared =1

  • bio-gel is negatively charged. As a result from that, negatively charged ions have a much more difficult time passing through the endothelium.
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8
Q

Components of the filtration barrier whose damage would result in hematuria
and proteinuria

-Physiological consequences a damaged filtration barrier would
have on body fluid oncotic and hydrostatic pressures.

A

Hematuria/proteinuria (presence of protein in urine)

  • Damaged filtration barrier => larger proteins will exit through. => lose a lot of albumin
  • decrease the colloid osmotic pressure of the capillaries => more water to enter into the interstitial tissue.
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9
Q

Summarize how anatomical arrangement of the kidney microcirculation influences
nephron function.

Contrast the physiological significance of blood flow through the renal cortex versus the medulla.

A

Cortex

  • contains renal corpuscle, coiled blood vessels, coiled tubules
  • arrangements: tubules and vessels intertwined randomly spaghetti

Medulla

  • straight blood vessel and straight tubules
  • arrangement: in parallel array like pencils

** kidney microcirculation is a separate network from kidney nephron and collecting duct system (they run parallel)

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10
Q

Filtered Load Equation

A

Filtered load of X= (plasma concentration of X) x GFR

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11
Q

Urinary excretion equation

A

Urinary excretion= filtered-reabsorbed-secreted

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12
Q

Tubular reabsorption equation

A

Tubular reabsorption= GFR- urinary excretion + secreted

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13
Q

How does tubular secretion occur?

A

excretion > filtration

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14
Q

Urine Excretion rate equation

A

urinary concentration of X (Ux) x urine flow rate (V)

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15
Q

What is renal clearance?

A

Volume of plasma completely cleared of a substance by the kidneys per unit time

FLOW RATE/ RATIO

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16
Q

Renal Clearance equation

A

Cx= (Ux x V)/ Px

17
Q

Glomerular Filtrate definition

It makes up how much of RBF? normal values>

A
  • volume of plasma/blood filtered through both kidneys per unit of time. (mL/min)
  • fluid filtered across glomerular capillaries in Bowman’s space
  • ~20% of RBF
  • 125ml/min
18
Q

Filtrate Fraction (definition, equation)

A
  • the fraction RBF that is filtered across glomerulus

FF= GFR/RBF

19
Q

As FF increases, what happens to oncotic pressure of EFFERENT arteriole? Why?

A

increases

bc it facilitates reabsorption of tubular fluid (decreased amount of fluid leaving the glomerulus)

20
Q

What can change FF?

- exm of clinical problems

A

GFR or RBF

decrease RBF due to hemorrhage or renal artery stenosis
-compensate-> increase GFR to make FF increase

21
Q

T/F Filtered load is the same as Filtration fraction

A

FALSE

Filtration Load
-rate in mg/min

Filtration Fraction
-ratio of GFR to RBF

22
Q

How will changes in filtration, reabsorption, or secretion will affect renal excretion of
each compound? (what are individual equations and what is it combined?)

A

Filtered load= GFR x Pna+

Reabsorption= filtered load-excretion

Excretion= V x Una

Percentage of filtered load is reabsorbed= reabsorption/ filtered load

Normal GFR= 125ml/min

23
Q

Inulin Characteristics

A
  • freely filtered
  • BUT neither reabsorbed nor secreted

amount excreted (urinary inulin concentration)= amount filtered (plasma inulin concentration)

24
Q

Creatinine Clearance

A
  • freely filtered
  • Metabolism of creatine phosphate in muscle
  • unlike inulin, a small amount is secreted
  • used to measure GFR but not an ideal marker
25
Q

How does Sympathetic Nervous System Stimulation increase blood pressure? (3)

A

1) arterial resistance vessels
a1 adrenoreceptor
powerful vasoconstriction afferent> efferent arteriole

2) Juxtaglomerular granular cells
B1 adrenoreceptors
Renin Release + RAAS

3) Tubular epithelial cells
a1 adrenoreceptors
Na-K ATPase
-increased Na+ reabsorption

26
Q

Acute(7) vs Chronic (3) effect of sympathetic stimulation

A

Acute

  • stimulate renin secretion by granular cells
  • angiotensin II exerts thirst
  • Angiotensin II restore systemic blood pressure via vasoconstriction
  • angiotensin II acts on EFFERENT ARTERIOLE
  • stimulate Na+ reabsorption in PCT and DCT
  • GFR is stabilized
  • Systemic BP is increased

Chronic

  • Decrease urinary output
  • Decrease urinary Na+ excretion
  • increased water intake
27
Q

Relationship between plasma creatinine concentration and GFR

A

Inversely proportional

28
Q

BUN: Creatinine Ratio (3)

A

1) 20:1
Problem: pre-renal
-BUN reabsoprtion is increased relative to creatinine
-exm. hypovolemia, dehydration, high protein diet

2) 10-20:1
Normal
-postrenal disease

3) <10:1
intrarenal
- reduced BUN reabsorption 
-decrease plasma level and lower ratio
- exm liver disease, low protein diet
29
Q

Para-aminohippuric acid

A
  • freely filtered by glomerular capillaries
  • can be used to estimate RBF
  • pah in plasma= pah in urine