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FA - Renal Physiology Flashcards

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1
Q

What is the course of the ureters in relation to the surrounding vasculature?

A

Ureters pass under the uterine artery and under the ductus deferens (water under the bridge)

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2
Q

What is the distribution of water in the body?

A

60% total body water; 40% ICF (2/3), 20% ECF (1/3)

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3
Q

What is the breakdown of extracellular fluid in the body?

A

1/4 plasma volume, 3/4 interstitial volume

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4
Q

What is the osmolarity of the body?

A

290 mOsm/L

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5
Q

What are the components of the glomerular filtration barrier?

A

Composed of

  • Fenestrated capillary endothelium (size barrier)
  • Fused basement membrane with heparan sulfate (negative charge)
  • Epithelial layer consisting of podocyte foot processes
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6
Q

How is the glomerular filtration barrier affected in nephrotic syndrome?

A

Charge barrier is lost, resulting in albuminuria, hypoproteinemia, generalized edema, and hyperlipidemia

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7
Q

How is renal clearance calculated?

A

Cx=Ux*V/Px

V=urine flow rate

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8
Q

What is an example of clearance < GFR and what does it indicate?

A

Urea; indicates net tubular reabsorption

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9
Q

What is an example of clearance = GFR and what does it indicate?

A

Inulin; indicates no net secretion or reabsorption

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10
Q

What is an example of clearance > GFR and what does it indicate?

A

Creatinine; indicates net tubular secretion

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11
Q

How can GFR be estimated?

A

Inulin clearance

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12
Q

How can effective renal plasma flow be estimated?

A

PAH clearance; underestimates by 10%

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13
Q

How is renal blood flow calculated?

A

RBF=RPF/(1-Hct)

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14
Q

What is a typical value for GFR?

A

100 mL/min

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15
Q

What is the equation for filtration fraction and what is an average value?

A

FF=GFR/RPF
=GFR/((1-Hct)(RBF))
= ~20%

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16
Q

What is the effect of prostaglandins on FF?

A

Causes dilation of afferent arteriole –>increased RPF, increased GFR, FF unch

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17
Q

What is the effect of NSAIDs on FF?

A

Inhibits actions of prostaglandins –> less renal perfusion; may precipitate acute renal failure

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18
Q

What is the effect of Ang II on FF?

A

Causes constriction of efferent arteriole –>decreased RPF, increased GFR –>increased FF (autoregulation)

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19
Q

What is the effect of ACEi on FF?

A

Prevents autoregulatory constriction of efferent arteriole –>decreased FF

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20
Q

What is the effect of afferent arteriolar constriction on RPF, GFR, FF?

A

Dec RPF, dec GFR, FF unchanged

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21
Q

What is the effect of efferent arteriolar constriction on RPF, GFR, FF?

A

Dec RPF, Inc GFR, Inc FF

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22
Q

What is the effect of increased plasma protein concentration on RPF, GFR, FF?

A

NC RPF, Dec GFR, Dec FF

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23
Q

What is the effect of decreased plasma protein concentration on RPF, GFR, FF?

A

NC RPF, Inc GFR, Inc FF

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24
Q

What is the effect of ureteral constriction on RPF, GFR, FF?

A

NC RPF, Dec GFR, Dec FF

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25
How do you calculate filtered load?
Filtered load = GFR x Px
26
How do you calculate excretion rate?
Excretion rate = V x Ux
27
How do you estimate reabsorption?
=Filtered-excreted
28
How do you estimate secretion?
=Excreted-filtered
29
What is the clearance of glucose?
Plasma level <160 mg/dL is completely reabsorbed by Na+/glucose co-transport
30
At what concentration of glucose are the transporters saturated?
Tm=350 mg/dL
31
How is glucose and amino acid metabolism affected in pregnancy?
Both are reduced, leading to glycosuria and aminoaciduria
32
How are amino acids reabsorbed in the proximal tubule?
AAs are reabsorbed via sodium-dependent transporters in prox. tubule
33
What is Hartnup's disease characterized by?
Deficiency of neutral AA (tryptophan) transporter -->cannot synthesize niacin -->pellagra
34
What substances are 67-70% reabsorbed in the proximal tubule?
Water, Na+, Cl-, Ca++
35
What substances are 100% reabsorbed in the proximal tubule?
Large macromolecules (glucose, AAs, phosphate), HCO3-
36
What substances are secreted in the proximal tubule?
H+, organic cations and anions
37
What are features of the proximal tubule?
- Contains brush border - Isotonic absorption - Generates and secretes ammonia (buffer for secreted H+)
38
What is the effect of PTH in the proximal tubule?
Inhibits Na+/phosphate co-transport -->increased phosphate excretion
39
What is the effect of ANGII in the proximal tubule?
Stimulates Na+/H+ exchange -->increased Na+, H2O, HCO3- reabsorption (permits contraction alkalosis)
40
What are features of the thin descending loop of Henle?
Passively reabsorbs water via medullary hypertonicity (impermeable to sodium) -->makes urine more hypertonic
41
What are features of the thick ascending loop of Henle?
- Actively reabsorbs Na+, K+, and Cl-. - Indirectly induces the paracellular reabsorption of Mg++ and Ca++ through (+) lumen pot'l generated by K+ backleak - Impermeable to H2O -->makes urine less concentrated
42
How much Na+ is reabsorbed in the TAL?
10-20%
43
What are features of the distal convoluted tubule?
-Actively reabsorbs Na+, Cl- --> makes urine more hypotonic
44
What is the effect of PTH on the DCT?
Increases Ca++/Na+ exchange -->increased Ca++ reabsorption
45
How much Na+ is reabsorbed in the DCT?
5-10%
46
What are features of the collecting duct?
Reabsorb Na+ in exchange for secreting K+ and H+ (regulated by aldosterone)
47
What is the effect of aldosterone on the collecting duct?
Acts on MR -->insertion of Na+ channel in luminal side
48
What is the effect of ADH on the collecting duct?
- Acts at V2 receptor -->insertion of aquaporin H2O channels on luminal side - Promotes reabsorption of urea
49
How much Na+ is reabsorbed in the collecting duct?
3-5%
50
What are some substances reabsorbed less quickly than water?
PAH, creatinine, inulin, urea, Cl-, K+
51
What are some substances reabsorbed at the same rate as water?
Na+
52
What are some substances reabsorbed more quickly than water?
Pi, HCO3-, AAs, glucose
53
What are three causes of increased renin production?
Decreased blood pressure (JG cells) Decreased Na+ delivery (MD cells) Increased sympathetic tone (B1 receptors on JG cells)
54
What are the effects of ANGII on vascular smooth muscle
Causes vasoconstriction -->increased BP
55
What are the effects of ANGII on the glomerulus?
Causes constriction of efferent arteriole -->increased FF to preserve renal function in low-volume states
56
What are the effects of aldosterone?
Increased Na+ channel and Na+/K+ pump insertion in principal cells -->increased K+ and H+ excretion to crease favorable Na+ gradient for reabsorption
57
What is the effect of ADH?
``` Increases H2O channel insertion in principal cells -->increased H2O reabsorption Regulates osmolarity (volume more important than osmolarity) ```
58
What is the effect of ANGII on proximal tubule Na+/H+ activity?
Na+, HCO3-, and H2O reabsorption (can permit contraction alkalosis)
59
What is the effect of ANGII on the hypothalamus?
Stimulates hypothalamus -->increases thirst
60
What is the effect of ANGII on the baroreceptors?
Limits reflex bradycardia
61
What is the effect of ANP?
Released from atria in response to increased volume; may act as a check on RAAS Relaxes VSMC via cGMP -->increased GFR, decreased renin production
62
What is the juxtaglomerular apparatus?
Modified smooth muscle of the afferent arteriole (JG) and distal convoluted tubule (MD); defends GFR via RAAS
63
What is the effect of beta blockers on the JGA?
Inhibits B1 receptors --> decreased renin release -->decreased BP
64
What are causes of high renin/high aldo in pt. with HTN and hypokalemia?
Secondary hyperaldosteronism: renovascular HTN, malignant HTN, renin-secreting tumor, diuretic use
65
What are causes of low renin/high aldo in pt. with HTN and hypokalemia?
Primary hyperaldosteronism (Conn's): aldo-secreting tumor, bilateral adrenal hyperplasia
66
What are causes of low renin/low aldo in pt. with HTN and hypokalemia?
Non aldo related causes: CAH, deoxycorticosterone producing adrenal tumor, Cushing syndrome, exogenous mineralocorticoid
67
What is the function of erythropoietin?
Released by interstitial cells in the peritubular capillary bed in response to hypoxia -->increased RBC production
68
What is the action of the kidney on 25-OH vitamin D?
Proximal tubules convert it to 1,25-(OH)2 vitamin D (active form) using 1a-hydroxylase (regulated by PTH)
69
What is the effect of ANP on kidney?
Causes inc GFR and inc Na+ filtration with NO COMPENSATORY Na+ reabsorption -->Na+ and volume loss
70
What is the effect of PTH on the kidney?
Causes inc. Ca++ reabsorption in DCT, dec. phosphate reabsorption in PCT, and increased 1,25(OH)2 vit D production
71
What is the effect of Digitalis on K+?
Shifts out of the cell -->hyperkalemia
72
What is the effect of Hyperosmolarity on K+?
Shifts out of the cell -->hyperkalemia
73
What is the effect of Insulin deficiency on K+?
Shifts out of the cell -->hyperkalemia
74
What is the effect of cell lysis on K+?
Shifts out of the cell -->hyperkalemia
75
What is the effect of acidosis on K+?
Shifts out of the cell -->hyperkalemia
76
What is the effect of beta-adrenergic antagonist on K+?
Shifts out of the cell -->hyperkalemia
77
What is the effect of hypoosmolarity on K?
Shifts into the cell -->hypokalemia
78
What is the effect of insulin on K+?
Increases Na+/K+ ATPase -->shifts into the cell -->hypokalemia
79
What is the effect of alkalosis on K+?
Shifts into the cell -->hypokalemia
80
What is the effect of a beta-adrenergic agonist on K+?
Increases Na+/K+ ATPase -->shifts into the cell -->hypokalemia
81
What is the effect of low serum Na+?
Nausea and malaise, stupor and coma
82
What is the effect of high serum Na+?
Irritability, stupor, coma
83
What is the effect of low serum K+?
U waves on ECG, flattened T waves, arrhythmias, muscle weakness
84
What is the effect of high serum K+?
Wide QRS and peaked T waves on ECG, arrhythmias, muscle weakness
85
What is the effect of low Ca++?
Tetany, seizures
86
What is the effect of high Ca++?
Renal STONES, pain in the BONES, abdominal pain (GROANS), and psychiatric disturbances (MOANS)
87
What is the effect of high Mg++?
Tetany, arrhythmias
88
What is the effect of low Mg++?
Decreased DTRs, lethargy, bradycardia, hypotension, cardiac arrest, hypocalcemia
89
What is the effect of low phosphate?
Bone loss, osteomalacia
90
What is the effect of high phosphate?
Renal stones, metastatic calcifications, hypocalcemia
91
What is the pH, PCO2, and HCO3- in metabolic acidosis?
Low pH, decreased PCO2 (immediate hyperventilation) and decreased HCO3-
92
How is compensated metabolic acidosis assessed?
Winter's formula: PCO2= 1.5[HCO3-] +8 +/-2
93
What is the estimated PCO2 compensation in metabolic acidosis?
1:1
94
What is the pH, PCO2, and HCO3- in metabolic alkalosis?
High pH, increased PCO2 (immediate hypoventilation) and increased HCO3-
95
What is the estimated PCO2 compensation in metabolic alkalosis?
1:2 (i.e. half the increase in bicarb)
96
What is the pH, PCO2, and HCO3- in respiratory acidosis?
Low pH, increased PCO2, and increased HCO3-
97
What is the estimated HCO3- compensation in respiratory acidosis?
1 pt in acute condition (i.e. 25 mEq/L) | 3 pts in chronic (i.e. 27 mEq/L)
98
What is the pH, PCO2, and HCO3- in respiratory alkalosis?
High pH, decreased PCO2, decreased HCO3-
99
What is the estimated HCO3- compensation in respiratory alkalosis?
2 pts in acute condition (i.e. 22 mEq/L) | 5 pts in chronic condition (i.e. 19 mEq/L)
100
What are the PCO2 and the HCO3- in a mixed resp/met acidosis?
Inc PCO2, decreased HCO3-
101
What are the PCO2 and HCO3- in a mixed resp/met alkalosis?
Dec PCO2, increased HCO3-
102
What is the Henderson-Hasselbach equation?
pH=6.1 + log [HCO3-]/(0.03*PCO2)
103
What are respiratory causes of acidemia?
Hypoventilation due to: airway obstruction, acute lung dz, chronic lung dz (COPD), opioids, sedatives, resp. muscle fatigue, structural
104
What are metabolic causes of acidemia?
Anion gap: MUDPILES | Non anion gap: hyperalimentation, Addison's, RTA, Diarrhea, acetazolamide, spironolactone, saline infusion (HARDASS)
105
What are respiratory causes of alkalemia?
Hyperventilation due to: early high altitude exposure, early salicylate toxicity, PE, PNA, CHF
106
What are metabolic causes of alkalemia?
Vomiting, antacid use, volume contraction (usu. with loop diuretic), mineralocorticoid/high GC
107
What defines type I RTA?
Defect in collecting duct (DISTAL) excretion of H+ leading to urine pH >5.5 Associated with hypokalemia and formation of Ca+ phosphate kidney stones
108
What defines type II RTA?
Defect in PROXIMAL tubule reabsorption of HCO3- leading to urine pH <5.5 May be seen with Fanconi syndrome Associated with hypokalemia and increased risk for hypophosphatemic rickets
109
What defines type IV RTA?
Hypoaldosteronism or lack of collecting tubule response to aldo causes HYPERKALEMIA -->impaired ammoniagenesis and decreased H+ buffering capacity Low urine pH

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