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Block 2; Week 4 > Keef 2 > Flashcards

Keef 2 Flashcards

1
Q

What is the equation for determining glomerular filtration?

A 
Filtration = K[(Pc + piT) - (PT + piC)]
Filtration = K [(favor factors) - (oppose factors)]
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2
Q

What are the 2 factors that favor filtration?

A

The capillary hydrostatic pressure

Oncotic pressure in the tubules

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3
Q

What are the 2 factors that oppose filtration?

A

The tubular hydrostatic pressure

Oncotic pressure in the glomerulus

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4
Q

What is the value of the oncotic pressure in the tubules usually? What does it mean if this isn’t the value?

A

Usu zero.

If not, means that proteins are leaking into the tubules…means that the barrier is breaking down. Bad sign.

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5
Q

What are the 2 factors that determine the K coefficient of the filtration equation for the glomerular capillaries?

A

permeability

surface area

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6
Q

Why does the net filtration in the glomerular capillary decrease as the length of the capillary increases…as you move along?

A

B/c the plasma oncotic pressure increases as you move along the capillary bed.

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7
Q

Why does the plasma oncotic pressure increase as you move along the length of the capillary?

A

b/c as you remove water thru filtration b/c of the high plasma hydrostatic pressure…you get a higher conc’n of proteins in the plasma. This raises the oncotic pressure in the plasma & limits the amount of water that can be filtered.

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8
Q

What happens to the glomerular hydrostatic pressure & the tubular hydrostatic pressure as you move along the length of the capillary?

A

The tubular hydrostatic pressure stays constant across the length.
The glomerular hydrostatic pressure decreases slightly (maybe b/c it is filtering out water?)

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9
Q

What are some of the difference b/w the glomerular capillary filtration situation & the skeletal muscle capillary filtration?

A

The glomerular capillary hydrostatic pressure is much higher to begin w/ than the capillary hydrostatic pressure in the skeletal muscle.
The skeletal muscle capillary hydrostatic pressure decreases much more dramatically than the glomerular hydrostatic pressure, which only decreases slightly.
The glomerular capillary only has a period of filtration.
The skeletal muscle capillary has a period of filtration & reabsorption (when the hydrostatic pressure dips below the oncotic pressure).

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10
Q

If the glomerular capillary doesn’t have any reabsorption, when does that happen?

A

The peritubular capillaries are where the reabsorption happens in the kidney. This is a low pressure capillary.

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11
Q

Why is the K (filtration coefficient) different in the glomerular capillary than other normal capillaries?

A

It is higher in the glomerular capillary than other normal capillaries. This is b/c this capillary is more permeable.

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12
Q

Which of the filtration factors would a urinary tract obstruction change & what would be the net result?

A

It would cause a backup & would increase the tubular hydrostatic pressure.
This would decrease net filtration.

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13
Q

Which of the filtration factors would hypoalbumineria change & what would be the net result?

A

This is a decrease in the amount of protein, specifically albumin, in the blood.
This would decrease the capillary oncotic pressure.
This would cause a net increase in the filtration.

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14
Q

Which of the filtration factors would diabetic nephropathy change & what would be the net result initially & after a period of time?

A

This would increase the permeability of the glomerulus to proteins b/c of a breakdown of the barrier. Thus, more proteins would leak out of the capillary & into the tubules.
Initially:
K would increase (most important factor)
oncotic pressure in tubules would increase
oncotic pressure in the capillary would decrease
Net filtration would increase.
After a period of time:
K would decrease b/c nephrons would be lost & surface area would decrease.
Net filtration would then decrease.

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15
Q

What happens to the capillary hydrostatic pressure in the glomerulus when you’re going in w/ the afferent arteriole & when you’re coming out w/ the efferent arteriole?

A

It decreases slightly over this distance b/c of the filtration of water.

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16
Q

What happens to the capillary oncotic pressure in the glomerulus when you’re going in & when you’re coming out?

A

It increases significantly b/c of the loss of water to the Bowman’s space. This increases the conc’n of the proteins.

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17
Q

How does the capillary hydrostatic pressure change coming out of the glomerulus @ the efferent arteriole & entering the peritubular capillary?

A

It decreases significantly b/c of the increase of resistance from the efferent arteriole.

18
Q

How does the capillary oncotic pressure change coming out of the glomerulus @ the efferent arteriole & entering the peritubular capillary?

A

It doesn’t change. No water or proteins have been exchanged w/i this distance.

19
Q

What happens to the peritubular capillary oncotic pressure going in & coming out?

A

It decreases. Makes sense b/c this is a site of reabsorption.

20
Q

Where are the peritubular capillaries found?

A

Surrounding the PCT or DCT.

21
Q

What is the order of structures/cells from the glomerular capillary side to the Bowman’s space side?

A

endothelium
basal laminae
podocytes
go thru the filtration slits

22
Q

Why is the top of the PCT pretty permeable?

A

B/c there aren’t a ton of proteins b/w the tight jcns of its epithelium.

23
Q

What are the things that allow for peritubular capillary reabsorption along the PCT?

A

The starling forces of it all.
Also…Na/K pump w/ energy on the PCT.
Water follows this in 2 ways: bulk flow (mainly) b/w the cells & a little thru the cells.

24
Q

How does some of the water get out of the PCT thru cells?

A

Aquaporins that aren’t regulated by ADH.

25
Q

What happens to reabsorption @ the peritubular capillaries from the PCT when there is a decrease in peritubular capillary hydrostatic pressure?

A

It increases.

26
Q

What happens to the reabsorption @ the peritubular capillaries from the PCT when there is a decrease in the peritubular capillary osmotic pressure?

A

It decreases.

27
Q

What happens to the peritubular capillary hydrostatic pressure & the peritubular capillary oncotic pressure when you contract the efferent arteriole? What does this do to the reabsorption into the peritubular capillaries?

A

Contract the efferent arteriole.
GFR will increase…more fluid in the Bowman’s space & higher conc’n of proteins make it to the peritubular capillaries.
Higher peritubular oncotic pressure
Lower peritubular hydrostatic pressure (w/ contraction)
Both of these factors will cause an increase in reabsorption @ the peritubular capillaries.

28
Q

The larger a molecule is the harder/easier it is to be filtered thru the glomerulus.

A

harder.

29
Q

Which molecules are easily filtered thru the glomerulus?

A

water
glucose
salt
inulin (upper border of freely moveable b/c pretty large radius)

30
Q

Given a certain radius of a molecule…which will most easily move across the glomerulus? Why?
Positively Charged Molecule
Neutral molecule
Negatively Charged Molecule

A

Positively Charged will most easily move across b/c of the anionic coat on the filtration barrier.
Neutral will move thru ok.
Negatively charged will not move thru easily b/c of the anionic coat.

31
Q

What is the percentage of the plasma that is filtered thru the glomerulus?

A

20%

32
Q

What is the definition of clearance?

A

The volume of plasma per minute from which something is totally removed.
Units: ml/min
**sort of the ability of the nephron to conc’n a substance.

33
Q

What makes inulin a good substance to approximate GFR?

A

It is freely permeable.

But it’s not reabsorbed or secreted.

34
Q

How is inulin used to approximate GFR?

A

The clearance of inulin is equal to GFR.

Cin=GFR

35
Q

What is the equation for clearance? What are the factors that you have to know?

A

Cx=Ux V/Px
The point here is that you know the conc’n of x in the urine & the volume of urine & that you know the conc’n of X in the plasma. This can be used to determine the clearance.

36
Q

What makes creatinine ideal & not so ideal as an approximation of GFR?

A 
Ideal:
It is freely permeable.
It is not reabsorbed.
Not Ideal:
It IS secreted.
37
Q

Although creatinine is secreted, what compensates for this & makes it a decent approximation of GFR?

A

The lab chemistry will usu overestimate levels of creatinine in the plasma.
This sorta cancels out the effect of secreted creatinine. Makes it a good approximation.

38
Q

What is one clinical disadvantage to using creatinine clearance as an approximation of GFR? For this reason what do many clinicians use?

A

disadvantage: you have to take plasma & urine levels of creatinine over a period of 24 hours.
Many clinicians use an estimate of creatinine clearance from just taking plasma creatinine levels & putting it into a fancy equation that factors in your race etc.

39
Q

What is the concept of filtered load? What is the equation?

A

The burden our body experiences or the energy expenditure it experiences by filtering a certain substance every day. Ex: sodium filtration takes a lot of energy b/c of the sodium potassium pump.
Filtered Load=GFR X Px

40
Q

What is the equation for fractional excretion? What is this value for sodium?

A

Fractional Excretion=Excretion Rate/Filtered Load

0.4% for sodium

41
Q

What is the equation for fractional reabsorption? What is this value for sodium?

A

Fractional Reabsorption=Reabsorption Rate/Filtered Load

99.6% for sodium

42
Q

About how much sodium do we excrete per day? How does this relate to the amount of sodium intake that is recommended?

A

2.4 grams of sodium

This is about how much we are recommended to consume so that we have a body balance.

Block 2; Week 4 (6 decks)

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