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HB2 Final > Week 13 -Renal > Flashcards

Week 13 -Renal Flashcards

1
Q

Where does the renal corpuscle live?

A

the cortex

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2
Q

Where does the proximal tubule start and end?

What structures does it connect?

A
  • starts in the cortex and ends in the medulla

- connects the corpuscle to the loop of Henle

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3
Q

Where does the loop of Henle live?
Which side is thin/thick?
What structures does it connect?

A
  • in the medulla
  • thin descending limb, thick ascending limb
  • it connects the proximal tubule to the distal convoluted tubule
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4
Q

Where does the distal convoluted tubule live?

What structures does it connect?

A
  • the cortex

- it connects the loop of Henle to the cortical collecting ducts

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5
Q

Where does the cortical collecting duct live?

What structures does it connect?

A
  • the cortex

- it connects the distal convoluted tubule to the medullary collecting duct

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6
Q

Where does the medullary collecting duct live?

What structures does it connect?

A
  • the medulla

- it connects the cortical collecting duct to the renal papilla

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7
Q

Outline the pathway of the nephron.

Where are each of the structures located?

A
  1. corpuscle- cortex
  2. proximal tubule- cortex to medulla
  3. loop of Henle- medulla
  4. distal convoluted tubule- cortex
  5. cortical collecting duct- cortex
  6. medullary collecting duct- medulla
  7. renal papilla- medulla
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8
Q

What type of nephrons make up the majority of the kidney?

What type are the minority?

A
  • majority: cortical

- minority: juxtamedullary

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9
Q

What are the structural differences between cortical and juxtamedullary nephrons?

A
  • cortical: glomerulus higher in the cortex, with a short loop of Henle
  • juxtamedullary: glomerulus near the cortex/medulla interface, long loop of Henle that goes deep into the medulla, and vasa recta off the peritubular capillaries goes with the loop of Henle to feed the medulla
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10
Q

Outline the pathway of blood flow to the nephron.

A
  1. afferent arteriole
  2. capillary tuft/glomerulus
  3. efferent arteriole
  4. peritubular capillary bed
  5. only in juxtamedullary: vasa recta that feeds the loop of Henle
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11
Q

What feeds the loop of Henle in juxtamedullary nephrons?

A

the vasa recta

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12
Q

Where is most of the blood supply to the kidney located?
What is it for?
Why is this signficant?

A
  • in the cortex (barely any in the medulla via the vasa recta)
  • blood mainly for filtration, not for O2
  • medulla lives on the brink of hypoxia and is sensitive to ischemia
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13
Q

Where in the nephron does filtration occur?

How does this happen?

A
  • in the glomerulus
  • blood comes in via the afferent arteriole and some plasma filters across into the urinary space, and the rest of the blood leaves out of the efferent arteriole
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14
Q

Describe the process of reabsorption.

A

much of the filtrate is taken back up from the tubular network to the peritubular capillaries

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15
Q

Describe the process of secretion.

A

substances are moved from the peritubular capillaries into the filtrate in the tubular network

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16
Q

Outline the order of the functional processes that happen in the kidney.

A
  1. filtration
  2. reabsorption
  3. secretion
  4. excretion
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17
Q

In regards to clearance, what would a high number tell you?

A

that the kidney is extremely efficient in removing that substance from the plasma

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18
Q

How much of the cardiac output do the kidneys receive?

A

25%

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19
Q

What is the pressure of ultrafiltration in the kidneys?

A 
Puf= Pgc - Pbs - Pigc + Pibs
(gc = glomerular capillaries; bs = Bowman's space)
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20
Q

What pressures drive towards filtration in the glomerulus?

A
  • the glomerular capillary hydrostatic pressure

- Bowman’s space oncotic pressure (usually zero)

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21
Q

What pressures resist filtration in the glomerulus?

A
  • glomerular capillary oncotic pressure (high)

- Bowman’s space hydrostatic pressure (very low)

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22
Q

How much body fluid is in each compartment?

A

60% in the ICF

40% in the ECF

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23
Q

What are the subdivisions of the ECF?

A

80% interstitial

20% plasma

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24
Q

What is the major cation of the ECF?

What is its normal concentration?

A
  • Na

- 140

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25
Q

What is the minor cation of the ECF?

What is its normal concentration?

A
  • K

- 4

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26
Q

What is the major cation of the ICF?

What is its normal concentration?

A
  • K

- 120

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27
Q

What is the minor cation of the ICF?

What is its concentration?

A
  • Na

- 15

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28
Q

What are the conjugate anions found in the ICF?

A
  • proteins

- organic phosphates

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29
Q

What are the conjugate anions found in the ECF?

A
  • Cl

- bicarb

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30
Q

What is the normal osmolarity of the ECF?

Of the ICF?

A
  • 285

- 285

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31
Q

What are the major components of osmolarity of the ECF?

A
  • Na
  • Cl
  • glucose
  • BUN
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32
Q

How does D5W work as a volume expander?

A

it acts as free water

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33
Q

What are the major functions of the kidney?

A
  • endocrine (EPO, vit D activation)
  • fluid and electrolyte balance
  • waste product removal
  • acid/base balance
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34
Q

Describe the feedback involved in EPO.

A

EPO made by kidneys when they sense a low tissue partial pressure of O2 in the kidney. EPO goes to the bone marrow and stimulates production of more RBCs. More RBCs carry more O2, which negatively feeds back to the kidneys.

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35
Q

What makes up the renal corpuscle?

A
  • glomerulus
  • Bowman’s capsule
  • Bowman’s space
  • afferent and efferent arterioles
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36
Q

Where do podocytes live?

What is their function?

A
  • surrounding the exterior surfaces of the capillary loops of the glomerulus
  • assist in forming the filtration barrier
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37
Q

Where is the only place you are likely to use an electron micrograph clinically?

A

to visualize the glomerular filtration barrier

38
Q

What is the function of the podocyte?

What is their net charge?

A
  • to maintain a size/charge barrier

- negative (repels negative things)

39
Q

How well/poorly is albumin filtered through the podoctyes?

Why?

A
  • essentially unfilterable

- it is at the edge of the size barrier, but also carries a highly negative charge

40
Q

How do you calculate clearance?

A

(urine concentration x flow rate) / plasma concentration

41
Q

What is a good marker for measuring effective renal plasma flow (ERPF)?
Why?
What makes measuring this way difficult?

A
  • PAH
  • it is removed entirely from the blood in a single pass through the kidney
  • PAH is not naturally occurring, so it requires a continuous infusion to maintain the steady state
42
Q

What is the normal value for effective renal plasma flow (ERPF)?
What marker is used?

A

650 ml/min (using PAH)

43
Q

Under what conditions does clearance of a substance equal GFR?

A

if the substance is freely filtered, but neither secreted nor reaborbed

44
Q

Describe the substances used to measure GFR.

What is the issue with each?

A
  • inulin, an exogenous polysaccharide. Requires continuous infusion for 24 hours to attain steady state and get collection.
  • creatinine, endogenous by-product of muscle metabolism. It is ever so slightly secreted, so the number gotten is an overestimate (which gets worse with lower renal function).
45
Q

What is the normal GFR for an adult with normal renal function?
What marker is used?

A

120 ml/min (creatinine)

46
Q

How do you calculate filtration fraction (FF)?

What does it measure?

A
  • GFR/ERPF

- how much you actually filtered vs how much went through

47
Q

How does oncotic pressure change across the glomerulus?
Why?
What does this mean?

A
  • it increases
  • you have the same amount of protein coming out, but less water (some was filtered), which raises the oncotic pressure of the blood leaving
  • filtration ends before you leave the glomerulus
48
Q

If you increase the filtration fraction (FF), how does that affect the oncotic pressure in the glomerulus?
The amount of water reabsorbed?

A
  • it increases the oncotic pressure

- it increases the amount of water reabsorbed

49
Q

To make an on-the-spot estimation, how are creatinine and GFR related?

A

they have an inverse logarithmic relationship

50
Q

What is Na absorption dependent on in the nephron?

A

the gradient developed by the Na/K ATPase in the basolateral membrane

51
Q

How can you change the following variables to decrease the serum creatinine:
GFR?
Muscle mass?
Fat mass?

A
  • increase GFR
  • decrease muscle mass
  • fat has no effect on serum creatinine
52
Q

How does the kidney handle an increase in systemic blood pressure.

A
  1. that causes increased renal blood flow, GFR increases
  2. afferent arterioles have stretch receptors that sense the increased blood flow
  3. cause vasoconstriction of the afferent arterioles, decreases the pressure, and decreases the GFR back to normal
53
Q

How does the kidney handle a decrease in systemic blood pressure?

A
  1. that causes a decrease in renal blood flow, GFR decreases
  2. kidney senses decreased blood flow and activates angiotensin II
  3. this preferentially vasoconstricts the efferent arterioles, causing an increase in hydrostatic pressure in the glomerulus
  4. this increases GFR at the expense of renal blood flow
54
Q

How does the myogenic reflex affect the FF?

How does angiotensin II?

A
  • no change (both decrease)

- increase FF (decrease blood flow, increase GFR)

55
Q

What things preferentially keep the afferent arterioles open?

A

prostaglandins

56
Q

What makes up the juxtaglomerular apparatus?

A
  • afferent arteriole
  • distal tubule
  • macula densa, specialized cells in the distal tubule
57
Q

What do JG cells produce?

A

renin

58
Q

What is the point of the JG apparatus?

A

to allow the kidney to recognize what is happening in the tubular network and feedback to what is happening in the glomerulus

59
Q

Describe tubuloglomerular feedback when there is increased GFR.

A
  1. increased GFR means there are more solutes in the filtrate
  2. the macula densa senses this increased solute concentration by seeing more NaCl
  3. macula densa sends a signal (adenosine) to the next door afferent arteriole, telling it to vasoconstrict
  4. this decreases the hydrostatic pressure and decreases the GFR back to normal
  5. the macula densa sees less solute concentration and releases the adenosine signal
60
Q

Describe tubuloglomerular feedback when there is decreased GFR.

A
  1. decreased GFR means there are fewer solutes in the filtrate
  2. macula densa sensees the decreased solute concentration by seeing less NaCl
  3. macula densa sends a signal to the JG cells to release renin (signal unknown)
  4. RAAS system activates to restore blood pressure and increase GFR back to normal
61
Q

How much of the ingested Na is excreted in a normal person?

A

usually less than 1%

62
Q

What is Na reabsorption dependent on at every level of the nephron?

A

the Na gradient developed and maintained by the Na/K ATPase in the basolateral membrane

63
Q

How does Na reabsorption work in the early proximal tubule?

A

it is coupled to both nutrient and bicarb reabsorption and depends on the Na/K ATPase gradient

64
Q

What is the proximal tubule really good at reabsorbing?

A
  • Na (70%)
  • water (to the same degree as Na, as proximal tubule is freely permeable to water)
  • amino acids (essentially all)
  • glucose (essentially all)
65
Q 
What are the following structure's permeabilities to water:
Proximal tubule?
Thick ascending limb?
Early distal tubule?
Late distal tubule?
Collecting duct?
A
  • PT: freely permeable
  • TAL: impermeable
  • early DT: impermeable
  • late DT: variably permeable
  • CD: variably permeable
66
Q

What things are not abosorbed in the early proximal tubule?

What does this do to their concentrations?

A
  • Cl and creatinine

- because water is absorbed without these things, their relative concentration increases

67
Q

What is the concentration of a solute in the final urine dependent on?

A

both on how much the solute is reabsorbed or secreted and on how much water is left

68
Q

Why is Cl important to the late proximal tubule?

A
  1. its high concentration drives the paracellular reabsorption of both Na and water
  2. it is linked to the secretion of organic acids back into the lumen
69
Q

Where is the NKCC2 found?
What does it do?
What is required for it to continue to function?
What is the net movement?

A
  • in the thick ascending limb
  • 1 Na, 1 K, 1 Cl, all in
  • because there is more Na than K, a K channel is present where K is recycled
  • more anions reabsorbed than cations (because the K channel)
70
Q

Why can Mg and Ca move via paracellular reabsorption in the thick ascending limb?

A

The NKCC2 and K channel pair gives the lumen a net positive electrical potential, helping to drive cations Mg and Ca out

71
Q

What is the thick ascending limb aka?

Why?

A
  • the diluting segment

- it pulls solutes, but not water

72
Q

What does the thick ascending limb do to the osmolarity of the tubular fluid?
Why?

A
  • it makes it hypoosmotic

- it pulls solutes, but not water

73
Q

What things does the thick ascending limb absorb?

A
  • Na
  • K (kind of, due to the K channel back out)
  • Cl (2 at a time via NKCC2)
  • Mg (paracellularly via the net positive electrical potential created)
  • Ca (paracellularly via the net positive electrical potential created)
74
Q

How does Na reabsorption work in the early distal tubule?

Why is this important?

A
  • via a thiazide-sensitive Na/Cl co-transporter

- it is a drug target

75
Q

Where do principle cells live?
What is their function?
How does it carry out that function?
What is that function linked to?

A
  • the late distal tubule and collecting duct
  • Na reabsorption
  • via ENaC (epithelial Na channel)
  • secretion of K
76
Q

What is the main job of the proximal tubule?
How does it accomplish that?
What else does the PT have a lot of?

A
  • bulk reabsorption
  • via a microvilli brush border in the lumen to greatly increase surface area
  • mitochondria (to fuel the energy-dependent transporters)
77
Q

What is the epithelium across most of the nepron?

What is the exception?

A
  • cuboidal

- thin descending limb = squamous

78
Q

What is the most active segment of the nephron for reabsorption?
2nd most active?

A
  1. proximal tubule

2. thick ascending limb

79
Q

What are the types of cells in the late distal tubule and collecting duct?
What are their functions?

A
  • principal cells: Na reabsorption

- intercalated cells: acid/base balance

80
Q

What are the responsibilities of the late distal tubule and collecting duct?

A
  • acidify the urine
  • determine the final concentratio of the urine (water balance)
  • dump excess K if necessary
81
Q

How do you calculate filtered load?

A

GFR x plasma concentration

“how much filtered per unit time”

82
Q

How do you calculate excretion rate?

A

urine flow rate x urine concentration

“how much lost to urine per unit time”

83
Q

How do you calculate fractional excretion?

A

clearance / GFR

“how much of what was filtered got excreted in urine”

84
Q

How is ECF volume primarily measured?

A

by looking at effective arterial blood volume

85
Q

How can you regulate ECF volume?

A
  • RAAS
  • sympathetic nervous system
  • atrial natriuretic peptide (ANP)
86
Q

What things stimulate renin release?

A
  1. direct sympathetic stimulation to B1 receptors
  2. decreased perfusion to the afferent arteriole
  3. indirectly via decreased NaCl delivery to the macula densa
87
Q

What are the effects of angiotensin II on the kidney?

What is the goal?

A
  • preferential efferent arteriole constriction causing decreased medullary blood flow and increased GFR
  • increased Na reabsorption in the proximal tubule

-to restore blood flow to the kidney and/or effective arterial blood volume

88
Q

Where is the AT1 receptor located?
What stimulates the AT1 receptor?
What does it do?

A
  • the proximal tubule
  • angiotensin II
  • stimulates the Na/K ATPase, the Na/H antiporter, and bicarb reabsorption on the basolateral side
89
Q

Out of angiotensin II and aldosterone, which seems to have the more dominant effect on the kidney?
Why?

A

aldosterone, because it is a steroid and changes transcription, which is a longer lasting change (even though it acts at the collecting duct and not the proximal tubule)

90
Q

Where does aldosterone act in the kidney?

What does it do?

A

-the collecting duct

  • stimulates the Na/K ATPase
  • leads to more channels for Na reabsorption
  • leads to more channels for K excretion
91
Q

What is the net action of aldosterone in the kidney?

A
  • more Na reabsorption

- more K excretion

92
Q

What effect does the sympathetic nervous system have on the kidney?

A
  • afferent arteriole constriction
  • increased renin release using B1 receptors
  • increases Na reabsorption via a1 receptors in the proximal tubule and thick ascending limb

HB2 Final (5 decks)

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