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Renal > Glomerular Filtration > Flashcards

Glomerular Filtration Flashcards

1
Q

What restricts the filtration of proteins from glomerulus?

A

Podocytes

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2
Q

What is normal GFR?

A

100 – 125 ml/min (20% of blood that come through at the glomerulus) [90 and above is normal]

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3
Q

What is the volume of Plasma Filtered per Day?

A

(60 min X 24 h) X 125 ml/min: 180 Liters

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4
Q

Where does the blood that does not get filtrated in the glomerulus go?

A

Blood that was not filtered enters peritubular capillaries surrounding the nephron from the same glomerulus [vasa recta or peritubular]

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5
Q

How is the high filtration rate in the glomerulus explained?

A

1) Large Surface Area
2) Extremely High Capillary Wall Hydraulic Conductivity (Glomerular Fenestrae, Porous Basement Membrane, Podocyte Filtration Slits)

3) High Intra-Capillary Pressure
4) High Plasma Flow Rate

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6
Q

What is a pathology where glomerular endothelial fenestrae are closed?

A

Preeclampsia:
Systemic VEGF inhibition due to Placental Hypoxia
Endothelial Fenestrae Close
GFR Declines

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7
Q

What does Albuminuria indicate?

A

ALWAYS indicates glomerular capillary wall damage

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8
Q

T or F: negative charged molecules are relatively more freely filtered than cations

A

False

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9
Q

Why are negative charged molecules not freely filtered?

A

The negatively charged mucinous protein coat (Glycocalyx) covering the Endothelium and Podocytes accounts for Charge Selectivity

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10
Q

Which part of the glomerulus is in charge of size selectivity?

A

Podocyte Filtration Slit Diaphragm and Basement Membrane Pores account for Size Selectivity

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11
Q

T or F: with even Massive Proteinuria, only a small fraction of potentially filtered albumin passes into the urine

A

T

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12
Q

What kind of MW markers are used for urine electrophoresis?

A

LZM = lysozyme, 15 kDa
TPI = Triose phosphate isomerase, 27 kDa
ALB = albumin, 66 kDa
IgG = immunoglobulin G, 150 kDa

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13
Q

What diseases result to non-selective proteinuria?

A

i. e. Diabetic Nephropathy

i. e. Glomerulonephritis

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14
Q

What disease results to tubular proteinuria (smaller filtered proteins low MW cannot be reabsorbed)

A

Fanconi Syndrome

Tubular toxicity; drugs

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15
Q

In which disease is the tubular absorption overwhelmed?

A

Renal tubular acidosis (kidneys fail to excrete acids into the urine, which causes a person’s blood to remain too acidic)

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16
Q

What would happen if the charges in the glycoprotein coat covering endothelial and podocytes were neutralized?

A

There would be albuminuria without immunoglobulins appearing in the urine [Igs too big]

17
Q

What would happen if the slit diaphragm proteins were defective?

A

There would be nonselective proteinuria; immunoglobulins and albumin would be present in urine.

18
Q

How is glomerular capillary pressure measured?

A

Measured by direct Micropuncture

19
Q

At the glomerulus capilaries, where is the oncotic pressure highest?

A

At the end

20
Q

When does filtration cease?

A

When (Pgc-Pbs) = πgc, filtration ceases (filtration pressure equilibrium)

Intracapillary Hydraulic Pressure (Pgc) is opposed by the Plasma Oncotic Pressure (πgc) and Bowman’s Space Hydraulic Pressure (Pbs)

21
Q

How is GFR calculated?

A

GFR = LpS x (Δ hydraulic pressure – Δ oncotic pressure)
= LpS x [(PGC - PBS) - (πGC - πBS)]

Lp = Permeability of the membrane
S = Glomerular Capillary Surface Area
PGC = pressure within glomerular capillary
PBS = pressure within Bowman’s space
πGC = oncotic pressure within capillary
πBS = oncotic pressure within Bowman’s space (~ 0)
22
Q

What is an easy way to calculate GFR?

A

GFR (ml/min) = (UCreat X UFlow rate)/PCreat

23
Q

Glomerular filtration would stop unless it had…?

A

High Plasma Flow Rate

24
Q

What happens to arterial tone in kidneys in response to acute hypertension?

A

afferent arteriolar resistance goes up by constriction

25
Q

What happens in Response to Volume Depletion

Or Low Systemic Blood Pressure

A

efferent arteriolar resistance goes up

due to constriction

26
Q

When does renal autoregulation fail and GFR falls?

A

Loss of Autoregulation in Response to:
Severe Volume Depletion: GFR falls
Example: Hemorrhage: Renal Nerve activity causes constriction of afferent arterioles, Angiotension II constricts efferent arterioles

27
Q

What are some mediators of GFR autoregulation?

A

A) Myogenic Response:
Local distension of afferent and efferent arterioles leads to myogenic adjustment in arteriolar tone

B) Tubuloglomerular Feedback
Macula densa ATP release proportional to tubular fluid salt concentration
ATP and/or Adensosine (produced from ATP) bind to vasoconstrictor receptors (purinergic, Adenosine A1 receptors) of afferent arterioles

C) Changes in Sympathetic NS activity
Alter afferent and efferent arteriolar tone

D) Vasoactive Mediators
Renin Release from Juxtaglomerular Cells
Angiotensin Production&raquo_space; Preferential effect on efferent arterioles.

E) Other Vasoactive Mediators
Prostaglandins
Nitric Oxide, Endothelin, etc.

28
Q

What would happen to GFR if you were on an Angiotensin II receptor antagonist and then developed severe diarrhea?

A

Diarrhea would activate Renin Release

But, Autoregulation would fail&raquo_space; Acute Renal Failure

29
Q

What are causes of autoregulation failure?

A

Chronic Hypertension
Inhibition of Angiotensin II
Combination Calcium channel blockers + Ang II Inhibition

30
Q

Where are macula densa cells found?

A

ascending distal tubule

31
Q

Where are juxtaglomerular cells found?

A

afferent arteriole

32
Q

T or F: GFR is independent of tubular flow rate

A

F

GFR changes in response to tubular flow rate (inverse relationship) via tubuloglomerular feedback

33
Q

What would happen to GFR if you were on an extremely low salt diet for 2 weeks?

A

1) Angiotensin II activation&raquo_space; Efferent Vasoconstriction
2) Increased Proximal Tubule Salt and Water Reabsorption
3) Reduced Tubuloglomerular feedback signal&raquo_space; Afferent Vasodilation
- -> Preservation of GFR

34
Q

What are causes of functional reduction in GFR?

A

Activation of vasoconstrictor systems

Loss of autoregulation

35
Q

What are causes of structural reduction in GFR?

A

Fibrosis or Sclerosis of Glomerular Capillary Loops (irreversible)
Inflammatory Injury of Glomerular Cells

Renal (5 decks)

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