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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

24
Q

What 2 factors influence GFR

A

Net Filtration pressure and filtration coefficient

25
What 2 things determine the filtration coefficient
Slit surface area and filtration barrier permeability
26
What is GFR constant over
Wide range of blood pressures
27
What is GFR primarily regulated by
Renal arterioles (afferent and efferent) - more at afferent
28
Autoregulation maintains a nearly constant GFR between what mean arterial blood pressures
80-180
29
How do the afferent and efferent arterioles regulate GFR
Vasoconstriction and vasodilation
30
What does vasoconstriction of afferent arteriole cause
Increases resistance, decreased renal blood flow, decreased capillary blood pressure, decreased GFR
31
What is dependent on overall resistance
Renal blood flow
32
What is overall resistance determined by
Resistance in both afferent and efferent arterioles
33
What happens with increased resistance in efferent arteriole
Decreased renal blood flow, increased capillary blood pressure, increased GFR - blood polls in glomerulus
34
What would happen if afferent arteriole resistance decreased and efferent stayed the same
RBF would increase, hydrostatic pressure increase, GFR increase
35
What are 2 auto regulatory mechanisms that maintain stable GFR in face of BP fluctuations
1. Myogenic response of afferent arterioles (Myogenic autoregulation) 2. Tubuloglomerular feedback
36
What does the auto regulatory mechanisms protect
The filtration barriers from high BP that would cause damage
37
What is Myogenic autoregulation
Constriction in responses to stretch of the vascular smooth muscle caused by increased blood flow
38
What is tubuloglomerular feedback
Local control pathway in which fluid flows through the tubule portion of the nephron influences GFR
39
Juxtaglomerular apparatus
Where nephron loops back on itself so ascending limb of loop of henle passes between afferent and efferent arterioles
40
What do the macula densa cells do
Sense increased amount of flow
41
What do the macula densa cells do
Sense distal tubule flow and release paracrine signals that affect afferent and efferent arteriole diameter
42
What do granular cells do
Secrete an enzyme involved in salt and water balance
43
How do macula densa cells sense change
Possibly increased NaCl transport or increased cilia movement
44
What other 2 factors influence GFR
Sympathetic neurons Hormones
45
How do sympathetic neurons influence GFR
Release norepinephrine that acts on a1 adrenergic receptors on both afferent and efferent arterioles leading to vasoconstriction
46
How do sympathetic neurons and hormones influence GFR
Integrating centers outside kidneys can override the local control mechanisms by altering resistance or filtration coefficient
47
When does sympathetic activation alter GFR
Sharp rapid drop in blood pressure Ex) hemorrhage or sever dehydration
48
What hormones influence GFR
Angiotensin II, vasoconstrictor Prostaglandins, vasodilators
49
How else can the hormones alter the filtration coefficient
Act on podocytes and/or mesangial cells
50
How do hormones affect podocytes
Change size of filtration slits altering permeability
51
How do mesangial cells alter the filtration coefficient
Contraction of these cells alter capillary surface area available

Bmsc 208 (33 decks)

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