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kidneys Flashcards

1
Q

What is vascular resistance?

A

Defines or dictates how much pressure we have. Pressure drives flow.

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2
Q

What is vascular conductance?

A

This is the inverse of vascular resistance

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3
Q

How does the circulatory system decrease overall resistance?

A

The system is organized in parallel which can lower overall resistance in comparison to a system organized in series.

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4
Q

What is the difference in cross-sectional area between the aorta and the capillaries?

A

aorta: 2.5 cm^2
capillaries: 2500 cm^2

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5
Q

how is velocity of blood flow measured?

A

velocity: blood flow/ cross sectional area

This explains why blood flow is so much faster in the aorta than in the capillaries.

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6
Q

What are the main high resistance vessels in the body?

A

small arteries and arterioles

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7
Q

proximal to the arterioles or before the arterioles would you expect pressure to be high or low?

A

High

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8
Q

Distal to the arterioles or after the arterioles would you expect pressure to be high or low?

A

Low

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9
Q

Describe laminar flow…

A

The ideal means of blood flow. Forward and orderly. Would expect the centermost blood in the vessel to flow the fastest as the blood adjacent to the vessel walls experiences resistance from those walls.

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10
Q

Which organ system gets way more blood flow than it needs?

A

The kidneys. They get 22% of the blood flow.

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11
Q

How can we manipulate Ohm’s law to calculate blood flow?

A

Flow = change in pressure / vascular resistance

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12
Q

What cells make up the capillaries and how thick are they?

A

endothelial cells. They are one cell layer thick.

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13
Q

What is the diameter and cross-sectional area of the aorta?

A

diameter: 2.5 cm
cross-sectional area: 4.5 cm^2

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14
Q

What is the diameter and cross-sectional area of the vena cava?

A

diameter: 3 cm
cross-sectional area: 18 cm^2 (there are two of these)

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15
Q

What is the pressure of blood in the arterial end of a capillary? The venous end?

A

pressure in the arterial end: 30 mmHg
pressure in the venous end: 10 mmHg

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16
Q

What is the “delta P” in the capillary or the pressure difference that is driving blood flow from the arterial end to the venous end?

A

20 mmHg

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17
Q

What are the four starling forces in the capillaries?

A
  1. hydrostatic capillary pressure: 30 mmHg (arterial end) and 10 mmHg (venous end)
  2. hydrostatic interstitial pressure: -3 mmHg (due to lymphatic system)
  3. plasma oncotic pressure: 28 mmHg
  4. interstitial fluid colloid osmotic pressure: 8 mmHg
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18
Q

What drives venous blood flow and lymphatic flow?

A

skeletal muscle contractions help move these one-way valve systems. Stop moving and these systems stop flowing and fluid can build up

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19
Q

What is Kf?

A

The capillary permeability coefficient (takes into account the surface area and fluid permeability or how porous the capillary membrane is)

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20
Q

What are the three main proteins that make up the plasma oncotic pressure?

A
  1. albumin
  2. globulins
  3. fibrinogen
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21
Q

Which three capillary starling forces favor filtration?

A
  1. hydrostatic capillary pressure
  2. interstitial fluid hydrostatic pressure (-)
  3. Interstitial fluid colloid osmotic pressure
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22
Q

Which capillary starling force opposes filtration?

A
  1. plasma oncotic pressure
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23
Q

What is the net filtration pressure at the arteriole end of the capillary? What does this mean?

A

13 mmHg this favors filtration as it is a positive number

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24
Q

What is the net filtration pressure at the venule end of the capillary? What does this mean?

A

-7 mmHg this favors reabsorption as it is a negative number

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25
Q

13 mmHg filtered and -7 mmHg reabsorbed… where does the rest of the filtered fluid go?

A

the lymphatic system

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26
Q

what is the average capillary blood pressure say somewhere in the middle of the capillary?

A

17.3 mmHg

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27
Q

What is the filtration rate of ALL of the glomerular capillaries combined?

A

125 mL/min

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28
Q

If blood flow is too low to the kidneys what does the afferent arteriole do?

A

dilates or relaxes

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29
Q

If renal blood flow is too high, what does the afferent arteriole do?

A

constricts

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30
Q

Which segment of the blood vessels in the kidneys has the highest vascular resistance?

A

Efferent arteriole

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31
Q

If the efferent arterioles constrict what would happen to glomerular colloid osmotic pressure?

A

The colloids would be more concentrated, the oncotic pressure would be higher.

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32
Q

If the efferent arterioles relax what would happen to glomerular colloid osmotic pressure?

A

The colloids would be less concentrated, the oncotic pressure would be less.

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33
Q

What is a filtration fraction and what is normal?

A

How much fluid is filtered, how much plasma has made it through the kidney. ~19% is normal

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34
Q

How do you calculate filtration fraction?

A

GFR / renal plasma flow (RPF)
125/660

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35
Q

How do you calculate the renal plasma flow?

A

CO= 5L/min
Renal blood flow (22% of CO) = 1100 mL/min
HCT= 0.40
plasma volume= 1-HCT (0.6)
Renal plasma flow= (0.6)(1100)= 660mL/min

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36
Q

If we constrict the afferent arteriole, what happens to the pressure in the glomerular capillaries and what happens to our GFR?

A

pressure in the capillaries decreases and our GFR decreases

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37
Q

If we relax the afferent arteriole, what happens to the pressure in the glomerular capillaries and what happens to our GFR?

A

pressure in the capillaries increases and our GFR increases

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38
Q

What happens to renal blood flow if we constrict the afferent arteriole?

A

Decreased renal blood flow

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39
Q

What happens to renal blood flow if the afferent arteriole is dilated?

A

increased renal blood flow

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40
Q

If we relax the efferent arteriole, what happens to the pressure in the glomerular capillaries and what happens to our GFR?

A

pressure in the glomerular capillaries decreases and the GFR decreases

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41
Q

If we constrict the efferent arteriole, what happens to the pressure in the glomerular capillaries and what happens to our GFR?

A

pressure in the glomerular capillaries increases and the GFR increases

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42
Q

What happens to renal blood flow if the efferent arteriole is dilated?

A

increased renal blood flow (dilation anywhere in the capillary system in the kidneys would increase renal blood flow)

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43
Q

What happens to renal blood flow if the efferent arteriole is constricted?

A

decreased renal blood flow

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44
Q

What is an example of a compound that gets filtered and partially reabsorbed?

A

Na+. We eat way more Na+ than we need. So only some of it gets reabsorbed

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45
Q

What is an example of a compound that gets filtered a little but gets completely reabsorbed?

A

Glucose (in a non-diabetic) patient.

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46
Q

Give an example of a compound that gets filtered a little and the gets heavily secreted out of the blood?

A

PAH or Para amino hippuric acid.

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47
Q

What is PAH a good diagnostic for and why?

A

Renal blood flow. Removal of PAH is highly dependent on renal blood flow.

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48
Q

What is the innermost layer of the glomerular capillaries made up of?

A

endothelial cells these are very permeable due to fenestrations

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49
Q

Describe the layers of the glomerular capillaries from the deepest to the outermost layer…

A

endothelial cells
basement membrane (connective tissue)
epithelial cells/ podocytes

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50
Q

What is significant about the basement membrane?

A

It has lots of negative charge which can repel negatively charged proteins to keep them from being filtered through the fenestrations

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51
Q

What is significant about the epithelial cells and podocytes?

A

these provide structural support which is important as pressure is higher. The podocytes have foot processes that have slit pores

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52
Q

Which is more filterable: a negatively charged sugar, neutral sugar or a positively charged sugar?

A

Most filterable: cation
Then neutral charge
Least filterable: anion

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53
Q

The kidney is responsible for long term regulation of lots of processes… name a few examples

A
  1. BP regulation
  2. pH by producing bicarb and getting rid of excess H+
  3. RBC via erythropoietin
  4. electrolyte regulation
  5. Vitamin D activation
  6. Blood sugar regulation
  7. Some drug clearance
  8. Waste removal of nitrogenous compounds like urea
  9. Osmolarity regulator
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54
Q

Name the arteries in sequence from the renal artery to the peritubular capillaries

A

renal artery–> segmental arteries–> interlobar arteries–> arcuate arteries–> interlobular arteries–> afferent arteriole–> glomerular capillaries–> efferent arteriole–> peritubular capillaries

55
Q

Name the vein in sequence from the peritubular capillaries to the renal vein

A

peritubular capillaries–> interlobular veins–> arcuate veins–> interlobar veins–> segmental veins–> renal veins

56
Q

where do we do the bulk of our filtration?

A

glomerular capillaries

57
Q

where do we do the bulk of our reabsorption?

A

peritubular capillaries

58
Q

What percent of our nephrons are cortical? and what percent are deep medullary nephrons?

A

90-95% are cortical
5-10% are deep medullary

59
Q

How many nephrons does each kidndey have at birth?

A

1 million nephrons per kidney (2 kidneys = 2 million total nephrons)

60
Q

What is the major feature of the blood vessels associated with the deep medullary nephrons (vasa recta)? And what is significant about this feature?

A

They have two ascending blood vessels for every descending blood vessel. This slows down the blood flow velocity which maintains a normal amount of solutes in the renal interstitial space which helps with reabsorption.

61
Q

What is a feature of the blood vessels associated with the cortical nephrons?

A

the peritubular capillaries and associated tubules of the cortical nephrons dip down into the outer medulla and are more tortuous.

62
Q

What nerve controls our bladder and bowels?

A

pudendal nerve

63
Q

What is the pneumonic to remember which spinal nerves control the pudendal nerve?

A

“S2,3,4 keeps stuff off the floor”

64
Q

What is the major risk of removing the prostate gland?

A

damage to the pudendal nerve

65
Q

Where is the macula densa located in the kidney? and what is it responsible for?

A

It’s located in the thick ascending loop of Henle. These are specialized pressure sensing cells.

66
Q

Describe the renal tubular structure from the corpuscle to the collecting ducts…

A

corpuscle–> proximal convoluted tubule–> proximal straight tubule–> thin descending limb–> thin ascending limb–> thick ascending limb–> distal convoluted tubule–> collecting duct (cortical–>outer medullary–> inner medullary)

67
Q

When the macula densa senses low BP how does it respond?

A

the macula densa are adjacent to juxtaglomerular cells, when the MD sense low BP they signal to the JM cells to release renin. Renin leads to an increase in angiotensin II levels which constricts the efferent arteriole–> increases pressure in glomerulus–> increases filtration–> restore blood flow

68
Q

What is renal clearance?

A

volume of plasma cleared of a compound per unit of time

69
Q

If the kidney reabsorbs lots of fluid but not the stuff being filtered what would we say about the renal clearance of that filtrate?

A

The renal clearance of that compound is pretty high (mL/min)

70
Q

If the kidney reabsorbs ALL of the compound along with the fluid that’s reabsorbed what would we say about renal clearance about that compound?

A

The renal clearance of that compound is low

71
Q

Which compound is the “gold standard” to finding GFR?

A

inulin

72
Q

What is usually used to estimate GFR?

A

creatinine

73
Q

why do we usually use creatinine clearance to measure GFR?

A

it’s easier, inulin is exogenous, in order to measure a true GFR, need to inject inulin into the body.

74
Q

what compound do we use to estimate renal blood flow?

A

PAH “para amino hippuric acid”

75
Q

Which compound is considered heavily secreted? How much is cleared by the kidneys?

A

PAH. 90% gets excreted.

76
Q

Which compound is considered completely filtered?

A

Inulin

77
Q

An increase in blood pressure overtime can reek havoc on our glomerular capillaries how?

A

increased BP can lead to stiffened and calcified arterioles. Podocytes are disrupted in the epithelium and fenestrations in the endothelium are widened.

78
Q

Where specifically does angiotensin II act?

A

It constricts both the afferent and efferent arteriole but has a net effect on efferent arteriole constriction. Increases glomerular pressure and GFR.

79
Q

Where specifically do drugs “in our medicine cabinets” primarily act on the kidneys?

A

These constrict the afferent arteriole more than the efferent arteriole. Decreasing GFR.

80
Q

Where specifically do pressors and vasodilators work?

A

on both the afferent and efferent arterioles.

81
Q

What would happen at the macula densa if BP was high?

A

Increased NaCl sensed by MD cells –> decrease Ang II –> dilate efferent arteriole

82
Q

What would happen at the macula dense if BP was low?

A

filtration deficiency –> MD cells see less NaCl –> increase Ang II –> constrict efferent arteriole

83
Q

How does the macula densa sense the filtration rate of the

A

by counting Na+ and Cl+ ions (a # not a concentration)

84
Q

If GFR is low, what happens at the MD cells?

A

filter less Na+ and Cl- and have a normal amount of Na+/Cl- reabsorption. This would result in a net lower Na+ and Cl- that reach MD cells. They see this and respond by increasing Ang II, constrict efferent arteriole, increase GFR.

85
Q

How does angiotensin II cause an increase in BP?

A

Increases the amount of Na+ reabsorbed by the proximal tubule reabsorbed increasing water retention in the blood increasing BP.

86
Q

Say you have an increased amount of Na+ reabsorbed at the proximal tubule, but GFR is normal what would happen at MD cells?

A

MD cells would think GFR is low as there is less Na+ and Cl- reaching the counters. This would increase Ang II and increase BP, causing the kidney to have a higher than normal GFR

87
Q

What is an example of what could increase Na+ reabsorption at the proximal tubule?

A

High glucose and high amino acids (coupled with Na+ transportation).

88
Q

How does uncontrolled diabetes lead to kidney problems?

A

Increased glucose leads to increased Na+ reabsorption at the PCT. There is less Na+ that reaches MD. The MD interpret this as a low GFR and take steps to increase GFR by releasing more ang II. (Hyperfiltration initiated by high blood sugar)

89
Q

Why can giving an ACE inhibitor or ARB help with hyperfiltration caused by diabetes?

A

ACEi and ARB’s decrease amount of circulating Ang II from uncontrolled diabetes induced hyperfiltration

90
Q

The side of the tubular cells in the proximal convoluted tubule on the side adjacent to the tubular lumen is called what?

A

Apical side

91
Q

The side of the tubular cells in the proximal convoluted tubule on the side adjacent to the interstitial fluid is called what?

A

basolateral side

92
Q

Where in the PCT is most of our glucose absorbed? By what transporters?

A

In the first segment of the PCT (S1 segment) 90% is absorbed by the SGLT2 transporters on the apical side and transported to the interstitium via GLUT2 transporters on the basolateral side.

93
Q

What is the exchange rate of the SGLT2 pumps and what is their affinity for glucose?

A

1 glucose for 1 Na+ (more efficient). Lower affinity.

94
Q

What is the exchange rate of the SGLT1 pumps and what is their affinity for glucose?

A

1 glucose for 2 Na+. Higher affinity.

95
Q

Where is the rest of our glucose absorbed in the PCT?

A

The remaining 10% is reabsorbed by the S2 and S3 segments of the PCT via SGLT1 transporters on the apical side and GLUT1 on the basolateral side.

96
Q

When does blood glucose start showing glucose in the urine?

A

At “threshold” somewhere a little less than 200 mg/dL

97
Q

At what blood glucose are our glucose transporters saturated?

A

At “transport maximum” somewhere are 300 mg/dL

98
Q

At what blood glucose will ALL of our extra glucose get excreted?

A

at about 300 mg/dL (when transporters are completely saturated)

99
Q

Where is the MD located?

A

at the very end of the thick ascending loop of Henle

100
Q

Which cells release renin?

A

juxtaglomerular cells?

101
Q

What is the rate limiting step of angiotensin II formation?

A

renin

102
Q

What is the primary effect afferent arteriole dilation has on the kidneys?

A

increased renal blood flow. Increasing GFR.

103
Q

What is the primary effect efferent arteriole dilation has on the kidneys?

A

increased glomerular hydrostatic pressure increasing GFR.

104
Q

What would speed up the Na+/K+ ATPase pump in the PCT?

A

Ang II

105
Q

What are the three pumps angiotensin II effects at the PCT?

A

Speed up Na/K pumps
Speed up Na/H counter-transport pumps
Speed up Na/Bicarb co-transport pumps

106
Q

How does Cl- get reabsorbed?

A

Na+ and water get reabsorbed transcellularly
Cl- follows Na+ and gets reabsorbed via the paracellular route

107
Q

What is another name for the net reabsorption pressure of 10 mmHg at the peritubular capillaries?

A

Bulk flow

108
Q

What compound is found in large quantities in the renal interstitial space to aid osmosis?

A

urea

109
Q

Where is the brush border and what does it do?

A

Its on the luminal side of the PCT cells. This increases SA 20fold. Allows for more transporters for reabsorption.

110
Q

What is the average membrane potential in the kidneys?

A

-70mV

111
Q

How does the body reabsorb protein that gets filtered?

A

via endocytosis or pinocytosis. The proteins get broken down to their amino acids and reabsorbed via endocytosis to the int. space and back into the peritubular capillaries

112
Q

How much protein do we filter at the glomerulus? How much gets reabsorbed and how much ultimately gets excreted in the urine?

A

1.8 grams of protein gets filtered. 1.7 grams gets reabsorbed and 100 mg shows up in the urine.

113
Q

What is the primary site of Na+ reabsorption in the PCT?

A

NHE (the Na+/H+ exchanger)

114
Q

What would happen if we gave someone a carbonic anhydrase inhibitor?

A

Bicarb wasting which would lead to acidosis.

115
Q

List three important functions of the proximal tubule?

A

Na+/Cl- and H20 reabsorption
glucose and amino acid reabsorption
Acid/base balance

116
Q

How is bicarb produced?

A

from glutamine (produced by the liver) and converted by proximal tubule cells to bicarb (HCO3-) and ammonium (NH4+)

117
Q

Why do people with liver failure have a difficult time with pH management?

A

can’t make as much glutamine in the liver

118
Q

Name the important urinary buffers?

A

Phosphate
Ammonium
Bicarb

119
Q

How does the parathyroid gland control the Ca2+ levels in the blood.

A

The parathyroid gland monitors extracellular Ca2+. If it’s low it increases PTH which encourages vit. D activation which picks up dietary Ca2+. Also increases the amount of Ca2+ reabsorbed by increasing Ca2+ channels in the PCT. PTH also stimulates bone breakdown to free up more Ca2+

120
Q

What do osteoclasts do?

A

Break down bone (Ca2+ storage place)

121
Q

What do osteoblasts do?

A

Build new bone

122
Q

What are some endogenous organic cations that are secreted in the PCT ?

A

ACh
Creatinine
DA
Epi
Histamine
5-HT
NE

123
Q

What are some exogenous organic cations that are secreted in the PCT?

A

Atropine
Isoproterenol
Morphine
Procaine
Quinine
TEA

124
Q

What type of antiporter/s do cations use when secreted in the PCT?

A

H+/cation counter-transport

125
Q

What type of antiporter/s do anions use to get secreted into the PCT?

A

alpha ketoglutarate/ Na+ cotransport and then aKG/Anion counter-transport

126
Q

What are some organic endogenous anions that get secreted into the PCT?

A

Bile salts
Hippurates
Oxalate
PG’s
FA’s

127
Q

What are some exogenous organic anions that are secreted in the PCT?

A

Furosemide
Penicillin
Salicylates

128
Q

How were the antiporter secretory processes for cations and anions discovered?

A

During WW2 someone noticed blood levels of penicillin would drop (kidneys excreted it too quickly) and if they gave the patient a synthetic hippurate with the penicillin it would stay in the bloodstream longer as the hippurates competitively inhibit the antiporters responsible for secreting the penicillin.

129
Q

How much water/ions/compounds are reabsorbed in the PCT?

A

2/3 of everything that was filtered at the glomerulus

130
Q

What is happening at the thin descending loop of Henle?

A

Water reabsorption (secondary place where water is reabsorbed second to the PCT)

131
Q

What is happening at the thin ascending loop of Henle?

A

Na+/Cl- reabsorption driven by ATP primary active transport

132
Q

What is happening at the thick ascending loop of Henle?

A

Minimal water reabsorption. Lots of reabsorption of Mg++,Ca++, Na+, K+.

133
Q

What role does the thick ascending loop of Henle have on the renal interstitium?

A

It contributes to the concentration of the renal interstitium.

134
Q

How are lizards able to live in the desert and on minimal water?

A

They have a much more concentrated renal interstitium and are able to reabsorb more water out the tubule to survive.

Advanced A & P (5 decks)

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