The Renal system lecture 2 Flashcards

1
Q

what is the ultrafiltration barrier composed of ?

A
  1. Fenestrated endothelium
  2. Basement membrane
  3. Podocytes
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2
Q

what does the fenestration pore of the glomerular endothelial cell prevent ?

A

prevents filtration of blood cells but allows all components of blood plasma to pass through

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3
Q

what does the Basal lamina of the glomerulus prevent ?

A

prevents filtration of larger proteins

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4
Q

what does the slit membrane between pedicels prevent ?

A

prevents filtration of medium-sized proteins

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5
Q

who described ultrafiltration ?

A

using micropuncture, wearn and richards described ultrafiltration

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6
Q

what is the definition of glomerular filtrate ?

A

the fluid formed by ultrafiltration

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7
Q

what does the term glomerular filtration rate or GFR refer to ?

A

The rate at which the 2 kidney’s form ultra filtrate is GFR.

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8
Q

what does the term single nephron GFR refer to ?

A

the rate at which a single nephron forms ultra filtrate

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9
Q

what substances are freely filtered?

A

substances of low molecular weight are freely filtered. water urea glucose inulin myoglobin

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10
Q

what molecules are retrcietd ?

A

large molecules

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11
Q

give me 3 examples of molecules that are restricted

A

haemoglobin, serum, albumin

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12
Q

what molecules are more restricted ? negatively or positively

A

negatively charged molecules like albumin

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13
Q

what governs GFR ?

A

a balance of hydrodynamic forces

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14
Q

what are the two forces that oppose each other that constitute the hydrodynamic forces ?

A
Hydrostatic pressure (plasma leaves capillaries because of pressure )
oncotic pressure beacause of the protein that remained  in the plasma  because of size and charge
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15
Q

why does oncotic pressure oppose hydrostatic force ?

A

because of capillary pressure

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16
Q

what does the term net filtration pressure refer to ?

A

small oncotic pressure from bowman’s space opposing hydrostatic pressure

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17
Q

what is Pc?

A

Capillary hydrostatic pressure Pc - the pressure that will force fluid out from the capillary

18
Q

What is Pi?

A

Interstitial hydrostatic pressure Pi - the pressure that will force fluid out from the interstitial space

19
Q

What is πc?

A

Capillary oncotic pressure πc - the osmotic pressure that will force the fluids to enter the capillary from the interstitial space

20
Q

What is πi?

A

Interstitial oncotic pressure πi- the osmotic pressure that will force the fluids to enter the interstitial space from the capillary

21
Q

what is fluid filtration determined by ?

A

Fluid filtration is determined by the difference of hydrostatic pressures across the capillary
Pc - Pi

22
Q

what is fluid reabsorption determined by ?

A

Fluid reabsorption is determined by the difference of osmotic pressures across the capillary
Πc - Πi

23
Q

in systemic capillaries is there a net flow out of capillaries ?

24
Q

what is the value of Pc in the renal corpuscle ?

25
what is the value of Pi in the renal corpuscle ?
15 mmHg
26
what is the value of Πc in the renal corpuscle ?
30 mm Hg
27
what is the value of Πi in the renal corpuscle ?
0.3 mmHg
28
what is the formula of GFR ?
GFR=[(PC –PBC)–(Πc–ΠBC)].K
29
whats the net glomerular filtration pressure ?
10 mmHg
30
what would an increase in Pc lead to ?
An increase in PC increases GFR
31
what would a decrease in Pc decreases GFR ?
A decrease in PC decreases GFR
32
what would an increase Pbc do ?
An increase in PBC decreases GFR, | such as stones in the urinary tract, or retention of urine
33
what would a decrease in ΠC lead to ?
A decrease in ΠC increases GFR, i.e. liver failure
34
what would an increase in ΠBC lead to ?
An increase in ΠBC decreases GFR, i.e. renal failure
35
how can GFR be measured ?
It can’t be measured, but it can be estimated. • By measuring the rate of excretion of substances that are: 1. Freely filtered. 2. Not reabsorbed or secreted by tubules. 3. Have no influence on renal function (e.g. blood flow) Inulin meets these criteria.
36
what is the definition of renal clearance ?
the volume of plasma completely cleared of a given substance in 1 min
37
what is the GFR for inulin clearance ?
120-130 ml/min for adult humans. in a day that is 180 litres of plasma filtered
38
why is inulin not convenient for clinical measurement of GFR?
it's concentration in the plasma is not steady - not accurate
39
what substance fits the criteria already found in plasma ?
creatinine - however small amounts of creatinine are secreted into the proximal tubule
40
Homeostasis requires kidneys to maintain a relatively constant GFR ?
Too high – substances pass too quickly and are not reabsorbed • Too low – nearly all reabsorbed and some waste products not adequately excreted
41
give me three reasons for renal failure ?
pre-renal (e.g poor blood supply) renal ( loss of nephrons or nephron function ) post-renal ( e.g blockage of ureter and lower tract)