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Bmsc 208 > Renal 2 > Flashcards

Renal 2 Flashcards

1
Q

What is the first step of urine formation

A

Filtration of plasma from glomerular capillaries into the kidney tubules

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2
Q

What remains in blood during filtration

A

RBCs and plasma proteins

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3
Q

What makes up filtrate

A

Plasma and dissolved solutes

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4
Q

How much of the plasma that enters bowman’s capsule is filtered

A

20% (filtration fraction)
80% continues to peritubular capillaries
Not all can be filtered (would turn to sludge)

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5
Q

How much of CO do kidneys receive

A

~ 20%
1L/min

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6
Q

How much of blood that kidney recieves is plasma

A

60%
.6L/min

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7
Q

How much of plasma is filtered

A

20% of the 60%
.12L/min

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8
Q

What is normal minute filtration rate

A

125 ml/min

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9
Q

Where do the bowman’s capsule and glomerulus exist within

A

The renal corpuscle

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10
Q

What is the triple filtration barrier

A
  1. Glomerular capillary endothelial cells (fenestrated)
  2. Basal lamina (Extracellular matrix)
  3. Podocyte endfeet)
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11
Q

What are podocytes

A
  • tiny extensions that form end feet that cover glomerular capillary walls
  • can contract or retract feet
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12
Q

Mesangial cells

A

Supportive connective tissue cell
- contract and reduce surface area

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13
Q

What can mesangial cells and podocytes do

A

Influence filtration

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14
Q

What 3 pressures govern filtration from glomerular capillaries into renal tubes

A
  1. Hydrostatic pressure
  2. Colloid osmotic (oncotic) pressure
  3. Bowman’s capsule hydrostatic pressure
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15
Q

Hydrostatic pressure

A

Pressure of blood in glomerular capillaries
- favours filtration (determines how much pushed out)
- ~55 mmHg

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16
Q

Colloid osmotic (oncotic) pressure

A

Pressure gradient due to presence of plasma proteins and opposes filtration
~30 mmHg

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17
Q

How does the presence of plasma proteins oppose filtration

A

Remain with glomerulus and water attracted to excess protein (pulls in)

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18
Q

Bowman’s capsule hydrostatic pressure

A

Fluid pressure of the small structure of nephron on the capillaries
opposes filtration
~15 mmHg

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19
Q

Calculation of net filtration pressure

A

Hydrostatic - oncotic - fluid pressure=

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20
Q

What is a glomerular filtration rate (GFR)

A

Volume of fluid that filters from the glomerular capillaries into the bowman’s capsules per unit time (usually /min)

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21
Q

What is normal GFR

A

~125mL/min or 180L/day

22
Q

How many times do the kidneys filter our entire plasma volume in a day

A

Plasma volume 3L
60 times per day

23
Q

If not reabsorbed how quickly would we run out of plasma

A

24 mins

24
Q

What 2 factors influence GFR

A

Net Filtration pressure and filtration coefficient

25
Q

What 2 things determine the filtration coefficient

A

Slit surface area and filtration barrier permeability

26
Q

What is GFR constant over

A

Wide range of blood pressures

27
Q

What is GFR primarily regulated by

A

Renal arterioles (afferent and efferent)
- more at afferent

28
Q

Autoregulation maintains a nearly constant GFR between what mean arterial blood pressures

A

80-180

29
Q

How do the afferent and efferent arterioles regulate GFR

A

Vasoconstriction and vasodilation

30
Q

What does vasoconstriction of afferent arteriole cause

A

Increases resistance, decreased renal blood flow, decreased capillary blood pressure, decreased GFR

31
Q

What is dependent on overall resistance

A

Renal blood flow

32
Q

What is overall resistance determined by

A

Resistance in both afferent and efferent arterioles

33
Q

What happens with increased resistance in efferent arteriole

A

Decreased renal blood flow, increased capillary blood pressure, increased GFR
- blood polls in glomerulus

34
Q

What would happen if afferent arteriole resistance decreased and efferent stayed the same

A

RBF would increase, hydrostatic pressure increase, GFR increase

35
Q

What are 2 auto regulatory mechanisms that maintain stable GFR in face of BP fluctuations

A
  1. Myogenic response of afferent arterioles (Myogenic autoregulation)
  2. Tubuloglomerular feedback
36
Q

What does the auto regulatory mechanisms protect

A

The filtration barriers from high BP that would cause damage

37
Q

What is Myogenic autoregulation

A

Constriction in responses to stretch of the vascular smooth muscle caused by increased blood flow

38
Q

What is tubuloglomerular feedback

A

Local control pathway in which fluid flows through the tubule portion of the nephron influences GFR

39
Q

Juxtaglomerular apparatus

A

Where nephron loops back on itself so ascending limb of loop of henle passes between afferent and efferent arterioles

40
Q

What do the macula densa cells do

A

Sense increased amount of flow

41
Q

What do the macula densa cells do

A

Sense distal tubule flow and release paracrine signals that affect afferent and efferent arteriole diameter

42
Q

What do granular cells do

A

Secrete an enzyme involved in salt and water balance

43
Q

How do macula densa cells sense change

A

Possibly increased NaCl transport or increased cilia movement

44
Q

What other 2 factors influence GFR

A

Sympathetic neurons
Hormones

45
Q

How do sympathetic neurons influence GFR

A

Release norepinephrine that acts on a1 adrenergic receptors on both afferent and efferent arterioles leading to vasoconstriction

46
Q

How do sympathetic neurons and hormones influence GFR

A

Integrating centers outside kidneys can override the local control mechanisms by altering resistance or filtration coefficient

47
Q

When does sympathetic activation alter GFR

A

Sharp rapid drop in blood pressure
Ex) hemorrhage or sever dehydration

48
Q

What hormones influence GFR

A

Angiotensin II, vasoconstrictor
Prostaglandins, vasodilators

49
Q

How else can the hormones alter the filtration coefficient

A

Act on podocytes and/or mesangial cells

50
Q

How do hormones affect podocytes

A

Change size of filtration slits altering permeability

51
Q

How do mesangial cells alter the filtration coefficient

A

Contraction of these cells alter capillary surface area available

Bmsc 208 (33 decks)

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