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renal > 2 – GFR and it’s Determinants > Flashcards

2 – GFR and it’s Determinants Flashcards

1
Q

Glomerular filtrate:

A

-large amounts of fluid and solutes that are filtered through the glomerular capillaries into Bowman’s capsule

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2
Q

All molecules are freely filtered through GFR except:

A

-proteins
-calcium (1/2 bound to proteins)
-FAs (bound to proteins)

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3
Q

How much of renal plasma flow is filtered?

A

-20%=FILTRATION FRACTION

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4
Q

Filtration fraction equation:

A

=GFR/renal plasma flow

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5
Q

What is the glomerular filtration rate (GFR) in humans?

A

-125ml/min=180L/day
*when you add a unit of time to the filtration fraction

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6
Q

What does the filtration rate depend on?

A
  1. Glomerular capillary filtration coefficient (Kf)
  2. Filtration forces (hydrostatic and colloid osmotic forces)
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7
Q

What are the 3 layers of the filtration barrier?

A

-endothelium of glomerular capillaries
-basement membrane of capillaries
-epithelial cells of Bowman’s capsule (podocytes)

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8
Q

What makes the filtration barrier very permeable? (3 different layers)

A
  1. Perforated endothelium (fenestrae)
  2. Permeable basement membrane (proteoglycans)
  3. Non-continuous epithelium with long foot-like processes with gaps in between (slit pores)
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9
Q

What is the composition of filtrate?

A

-water and solutes=same as inside of glomerular capillaries as it is so permeable

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10
Q

How does size of molecules effect filtration in the glomerulus?

A

-smaller=pass through easier
Ex. big molecules=slower=proteins

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11
Q

How does molecular charge of molecules effect filtration in glomerulus?

A

*all 3 layers have a negative charge
-those with negative charge=less filterable due to electrostatic repulsion

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12
Q

Plasma proteins and filtration in glomerulus?

A

-very limited due to larger size and negative molecular charge
Ex. myoglobin and albumin=not found in urine

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13
Q

What determines the filtration of molecules of smaller sizes?

A

-less for those with negative charge

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14
Q

Glomerular capillary filtration coefficient (Kf):

A

-indicator of membrane permeability and SA
-can’t be measure directly
-constant under normal conditions

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15
Q

GFR equation:

A

=Kf x net filtration pressure

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16
Q

What are the 4 types of forces in the glomerular capillaries and Bowman’s capsule that affect the filtration?

A
  1. Glomerular hydrostatic pressure (Pg)
  2. Bowman’s capsule hydrostatic pressure (Pb)
  3. Colloid osmotic pressure of glomerular capillaries (piG)
  4. Colloid osmotic pressure of Bowman’s capsule (piB)
    *net filtration pressure may change under physiological conditions
17
Q

What are the forces of glomerular capillaries and Bowman’s capsule that promote filtration?

A

-glomerular hydrostatic pressure (Pg)
-colloid osmotic pressure of Bowman’s capsule (piB)=usually ZERO as proteins aren’t getting through

18
Q

What are the forces of glomerular capillaries and Bowman’s capsule that opposes filtration?

A

-Bowman’s capsule hydrostatic pressure (Pb)
-colloid osmotic pressure of glomerular capillaries (piG)=proteins!

19
Q

What pathological conditions cause a change in Kf?

A

-hypertension and diabetes
>increase thickness of basement membrane=REDUCES Kf

20
Q

What pathological changes causes a change in glomerular hydrostatic pressure?

A

-blockage of the ureter=increases Pb
Ex. kidney stones

21
Q

What is the pressure in afferent arterioles vs. efferent arterioles of glomerular capillaries?

A

-afferent: 28mmHg
-efferent: 36mmHg
*average=32mmHg

22
Q

What causes a change in colloid osmotic pressure of glomerular capillaries?

A

-changes in concentration of proteins in glomerular capillaries
1. Increased colloid osmotic pressure of arterial plasma
2. Changes in filtration fraction
>if more plasma is filtered=protein concentration in glomerular capillaries increases)

23
Q

Glomerular hydrostatic pressure (Pg)

A

*primary factor for physiological regulation of GFR

24
Q

What does increasing the arterial pressure due to the glomerular hydrostatic pressure (Pg)?

A

-increases Pg

25
Q

What does increasing arteriole resistance (constriction) due to glomerular hydrostatic pressure (Pg)?

A

-decreases Pg

26
Q

What does increasing efferent arteriole resistance (constriction) due to glomerular hydrostatic pressure?

A

-increases Pg

renal (15 decks)

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