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FHB Mikayla > Unit 2, L12 Renal Filtration and Blood FLow > Flashcards

Unit 2, L12 Renal Filtration and Blood FLow Flashcards

1
Q

What is the glomerular filtration barrier

A

A selective barrier, highly permeable to water and small solutes. It is impermeable to large substances in the blood (RBCs, WBCs, and proteins), and glomerular filtration is an ultrafiltrate of plasma

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2
Q

What is the glomerular filtration barrier composed of?

A

Fenestrated capillary endothelium, fused basement membrane with a negative charge barrier, and podocyte foot processes - slit diaphragm

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3
Q

Why can’t albumin cross through the filtration barrier?

A

It is small enough to fit through the fenestrations but the basement membrane is negatively charged so it can’t fit through

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4
Q

What factors affect the glomerular filtration barrier?

A

Molecular size of the molecules and electrical charge of molecules

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5
Q

How much of the RPF passes through into the Bowman’s space?

A

The filtration fraction is GFR/RPF, which is about 20%

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6
Q

Does glucose go through the glomerular filtration barrier?

A

Yes, as glucose gets filtered and completely reabsorbed

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7
Q

Do large proteins go through the glomerular filtration barrier?

A

No, they are too large to fit through the fenestrations

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8
Q

What is the equation for the rate of filtration

A

Rate of filtration = hydraulic permeability * surface area * NFP

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9
Q

What is NFP

A

Net Filtration Pressure, its the algebraic sum of the Starling forces that favor and oppose the glomerular filtration

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10
Q

What is the equation for Kf

A

Permeability GC * Area GC

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11
Q

What is the equationi for GFR

A

GFR = Kf * NFP

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12
Q

What is Kf

A

Filtration coefficient

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13
Q

Is total renal vasculature resistance high or low? Why?

A

Low, because everything is arranged in parallel

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14
Q

P GC (starling forces) means what

A

Hydrostatic pressure in the GC (+P GC) will push filtrate out of the blood and into the BS

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15
Q

P BS (starling forces) means what?

A

P BS is hydrostatic pressure in BS (- P BS) and will push filtrate out of BS and back into blood

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16
Q

pi GC (starling forces) means what

A

Pi GC is oncotic pressure in GC (-pi GC), which will pull filtrate out of BS and back into the blood

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17
Q

pi BS (starling forces) means what

A

Pi BS is oncotic pressure in the BS (+ pi BS = 0), which will pull filtrate out of blood into BS

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18
Q

What is the equation for net filtration pressure?

A

Net filtration pressure = P GC - P BS - pi GC + pi BS

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19
Q

What does the overall equation for GFR become after adding in starling forces?

A

GFR = Kf * (P GC - P BS - pi GC + pi BS)

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20
Q

Which pressure is greater on one end of the arterioles?

A

Oncotic pressure in the glomerular capillaries, stronger near the efferent arterioles

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21
Q

As arterial blood flows through glomerular capillaries, from afferent to efferent, what happens with P GC

A

It will fall slightly, from 60 to 58 mmHg

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22
Q

As arterial blood flows through glomerular capillaries, from afferent to efferent, what happens with Pi GC

A

It will increase greatly, from 28 to 35 mmHg, due to the concentration of proteins that are not being filtered

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23
Q

As arterial blood flows through glomerular capillaries, from afferent to efferent, what happens with pi BS

A

It will stay around 0, because no proteins filter out and the few that do get reabsorbed by pinocytosis

24
Q

As arterial blood flows through glomerular capillaries, from afferent to efferent, what happens with P BS

A

This will remain around 15 mmHg as the pressure here is needed to drive urine through the entire kidney, all the way to the bladder

25
Q

What is the starling force that favors filtration and what is the average value for it

A

Glomerular capillary blood pressure (P GC) and it is normally 60 mmHg

26
Q

What are the starling forces that oppose filtration and what are their average values

A

1) Fluid pressure in Bowman’s space (P BS) and its normal value is 15 mmHg
2) Osmotic force due to protein in plasma (pi GC) and its normal value is 29 mmHg

27
Q

What is the overall net glomerular filtration pressure

A

16 mmHg, favoring filtration

28
Q

Prerenal diseases that affect the GFR

A

Heart failure or hemorrhage, both of which would decrease effective circulating volume, which would decrease GFR

29
Q

Intrarenal diseases that affect the GFR

A

The immune complex deposition in glomerulus, leads to a decreased GFR. Examples being glomerulonephritis, proteinuria

30
Q

How would leaky glomerular capillaries affect GFR

A

Increase GFR by increasing Kf

31
Q

Postrenal diseases that may affect the GFR

A

Kidney stones would increase P BS, which would decrease GFR

32
Q

What is glomerulonephritis

A

When an immune complex, like from strep, binds to the basement membrane and causes inflammation of capillaries. Loss of glomerular integrity results in RBCs and casts in urine

33
Q

What are urinary casts

A

Cylindrical shaped aggregations from distal nephron, seen with low urine flow, acidic conditions, and proteinuria

34
Q

Renal cortex gets what percentage of renal blood flow

A

90%

35
Q

Outer medulla gets what percentage of renal blood flow

A

8%

36
Q

Inner medulla gets what percentage of renal blood flow

A

2%

37
Q

Average value for renal blood flow

A

1200 mL blood/min

38
Q

Hydrostatic pressure decreases from __________ to _________

A

From renal artery to renal vein

39
Q

Hydrostatic pressure has the largest decreases where

A

In the afferent and efferent arterioles, as they have high resistance

40
Q

Oncotic pressure increases along _________

A

The glomerular capillaries, as plasma proteins are concentrated during filtration

41
Q

Oncotic pressure decreases ___________

A

Decreases along peritubular capillaries, as plasma proteins are diluted during reabsorption

42
Q

What happens if you constrict the afferent arteriole

A

Decrease in renal blood flow, decrease in P GC, decrease in GFR

43
Q

What happens if you constrict the efferent arteriole

A

Decrease in renal blood flow, leads to an increase in P GC, leading to an increase in GFR

44
Q

What happens if you dilate the efferent arteriole

A

Increase in renal blood flow, leads to a decrease in P GC, leading to a decrease in GFR

45
Q

What happens if you dilate the afferent arteriole?

A

Increase in renal blood flow, increase in P GC, leads to an increase in GFR

46
Q

What is autoregulation of GFR and RBF

A

Maintaining GFR and RBF relatively constant in the face of changing arteriole blood pressure

47
Q

GFR and RBF will be (increased or decreased) when arterial blood pressure is > 180 mmHg

A

Increased

48
Q

GFR and RBF will be (increased or decreased) when arterial blood pressure is < 100 mmHg

A

Decrease

49
Q

At what point does renal shutdown occur?

A

< 70 mmHg

50
Q

At what point does renal death occur?

A

0 mmHg

51
Q

What is the intrinsic regulation for the GFR and RBF?

A

1) Intrinsic (vasoconstrictor and vasodilator) factors
2) Myogenic hypothesis
3) Tubuloglomerular feedback

52
Q

What is the extrinsic regulation of GFR and RBF

A

1) Sympathetic nervous system
2) Blood borne or endogenous substances (ang II)
3) Stress factors (hemorrhage)

53
Q

What are some of the vasoconstrictors for autoregulation

A

Sympathetic nervous system, catecholamines, ang II (extrinsic), and endothelin (intrinsic)

54
Q

What are some vasodilators for RBF and GFR

A

Prostaglandins (intrinsic), NO (intrinsic), bradykinin, and dopamine

55
Q

Explain the extrinsic regulation flow chart

A

Hemorrhage leads to a drop in arterial blood pressure. This leads to two things. 1) increased renin secretion, which will increase plasma and renal renin. This will then increase plasma and renal ang II. 2) an increase in activity of renal sympathetic nerves. Together, these will both cause constriction of renal arterioles. This will decrease RBF and GFR, and decrease renal excretion of sodium and water. Additionally, Ang II will increase tubular sodium and water reabsorption and facilitate the decreased excretion. Taken together, all of these will increase arterial blood pressure

FHB Mikayla (26 decks)

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