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Block E -- Renal > Physiology Lecture 1 and 2 -- Kidney Function > Flashcards

Physiology Lecture 1 and 2 -- Kidney Function Flashcards

1
Q

4 hormones secreted by the kidney

A
  • Renin
  • Angiotensin II
  • Erythropoietin
  • Activated vitamin D
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2
Q

Renal blood flow

A

1 L/min (20% of CO)

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3
Q

3 layers in the glomerular endothelium that separate the circulating blood from the capillary space

A
  • Innermost = capillary endothelial cell
  • Middle = collagenous basement membrane
  • Outer = podocyte
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4
Q

6 constituents of the ultrafiltrate

A
  • Water
  • Electrolytes
  • Urea
  • Cr
  • Sugar
  • Amino acids
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5
Q

3 substances that should not appear in the ultrafiltrate

A
  • Cells
  • Proteins
  • Fats
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6
Q

Charges of the capillary basement membrane and podocytes

A

Negative

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7
Q

2 conditions in which abnormal amount of albumin will cross the glomerular basement membrane

A
  • Damage to the structure of the filtration barrier
  • Loss of negative charge of the filtration barrier
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8
Q

Define GFR

A

The amount of plasma filtered through the glomeruli per unit time (most often refers to all nephrons collectively)

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9
Q

How to dose medication excreted by the kidneys if a patient has low GFR

A

Los GFR = less medication or simply avoid certain meds

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10
Q

3 forces involved in glomerular filtration

A
  • Pgc = capillary pressure
  • Pt = tubular pressure
  • πgc = oncotic presusre (from unfiltered proteins in tubule)
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11
Q

3 characteristics of creatinine that make it a good estimate of GFR

A
  • Has stable plasma concentration
  • Freely filtered at the glomerulus
  • Stays in the tubule to be excreted (is not reabsorbed)
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12
Q

Normal GFR

A

~100 mL/min

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13
Q

Equation for creatinine clearance

A
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14
Q

Relationship between plasma Cr concentration and GFR

A

Inverse

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15
Q

If a patient’s GFR falls by 50%, what happens to the newly produced creatinine?

A

Newly produced creatinine accumulates until the filtered load again equals the rate of production (i.e. when the plasma Cr has increased by x2)

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16
Q

4 formulae to estimate creatinine clearance in the hospital

A
  • CKD epi
  • MDRD
  • COckroft Gault
  • Schwartz
17
Q

Cockroft Gault equation

A

NOTE: GFR must be in a steady state to use formula

18
Q

What is a specific application for the Schwartz formula?

A

Can be used for children

19
Q

What is a specific application for CKD-epi?

A

Screening (can estimate GFR without taking any actual measurements like weight)

20
Q

What is a specific application for the Cockroft Gault equation?

A

More specific estimate of GFR since it takes into account body mass, so can use on patients who are amputees or have abnormal body weight (i.e. low BCM)

21
Q

How does Cr clearance overestimate GFR?

A
  • It is secreted in the proximal tubule
  • –> Cr excretion exceeds Cr filtration by 10 - 20%
22
Q

Perfect molecule to estimate GFR

A

Inulin (filtered, not reabsorbed, not secreted)

23
Q

2 limitations to creatinine clearance as an estimate of GFR

A
  • Cr production varies with muscle mass (sarcopenia in older people ages 50 - 90)
  • Varies with meat intake (may have high Cr due to eating steak 3x per day)
24
Q

Urea levels in hypovolemic states

A

Rises out of proportion to Cr, so can be useful in assessing patients with acute renal failure

25
Q

3 autoregulation mechanisms to maintain GFR

A
  • Myogenic reflex = vasospasm of afferent arteriole (50% of autoregulation)
  • Tubuloglomerular feedback
  • Glomerular vasoconstrictors and vasodilators
26
Q

Describe the myogenic reflex

A
  • BP too high = afferent arteriole sm contracts
  • BP low = afferent arteriole stretches/dilates
27
Q

Describe tubuloglomerular feedback

A
  • Macula densa samples fluid (senses Cl concentration –> low = glomerular blood flow is low)
  • Signals to arteriole to open up (possibly using adenosine)
  • Juxtaglomerular cells also release renin
28
Q

Describe the effect of glomerular vasoconstrictors and vasodilators

A

In situations of a major drop in systemic BP:

  • Activation of sympathetic nervous system
  • Increase production of angiotensin II

Angiotensin II constricts efferent arterioles more than afferent arteriole to preserve glomerular capillary P

29
Q

Main purpose of the tubules

A

Reabsorb most of the water and solute of the filtrate back from the tubules into the circulation

30
Q

Define resorption

A

Move from urine back to the body (apical –> basolateral)

31
Q

Define secretion

A

Moves from the blood to the urine (basolateral –> apical)

32
Q

Define excretion

A

Leaves the body in the urine

33
Q

Only place in the body where a capillary does not drain into a vein

A

Glomerulus (drains into efferent arteriole)

34
Q

General effect of ADH on kidney

A

Induce collecting duct water permeability by insertion of aquaporins

35
Q

6 functions of the proximal tubule

A
  • Na+ reabsorption
  • Reabsorption of almost all glucose, phosphate, amino acids
  • Reabsorption of bicarbonate
  • Secretion of uric acid and organic acids (i.e. drugs)
  • Water reabsorption
  • Calcium, potassium and chloride movement along their concentration gradients
36
Q

How does reabsorption occur in the proximal tubule?

A

Basically, it is all coupled to their respective Na+ cotransporters

37
Q

3 functions of the Loop of Henle

A

Separation of Na and water movement –> countercurrent mechanism

  • Thin descending limb permeable to water
  • Thick ascending = Na+ out of lumen via Na-K-2Cl cotransporter in apical side

+ Ca and Mg reabsorption

38
Q

2 functions of the distal convoluted tubule

A
  • Reabsorption of Na via Ca-Cl cotransporter
  • Calcium reabsorption (via channel in apical side and exchanger in basolateral side)
39
Q

4 functions of collecting duct

A

Principals cells

  • Na and water reabsorption
  • K+ secretion
  • Selective Na+ channels under aldosterone control

Intercalated cells

  • Water transport (site of ADH action)

Block E -- Renal (4 decks)

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