Renal Basics Flashcards

1
Q

75% of gluconeogenesis occurs in the liver

25% of gluconeogenesis occurs in the ______

A

kidneys

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2
Q

Renal plasma flow rate

A

amount of plasma that passes through kidneys per minute

~600 mL/min

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3
Q

Total blood flow through kidneys per minute

A

~1000 mL/min

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4
Q

Macula densa

A

cells located at junction of afferent and efferent arterioles

sense changes in sodium concentration

  • can cause vasodilation
  • renin release control from juxtroglomerular cells
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5
Q

Mesangium

A

specialized sm muscle cells that regulate bloodflow in the kidney

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6
Q

Molecules up to what size are freely filtered into Bowman’s space?

A

< 7,000 D

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7
Q

Molecules up to what size will be completed excluded from filtration into Bowman’s space?

A

> 70,000

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8
Q

What is the approximate size of albumin?

A

66,000 D

*some escapes into Bowman’s space and is lost in the urine

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9
Q

Is albumin lost into the urine?

A

yes, some

MW = 66,000 D

some filtered up to 70,000 D

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10
Q

Charge of glomerulus basement membrane

A

negative

+ charges more easily filtered into Bowman’s space

  • charges less easily filtered into Bowman’s space
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11
Q

Normal values for:

Pgc (glomerular capillary)

Pbs (Bowman’s space)

πgc

πbs

A

Pgc = 60

Pbs = 15 (because backing up to filtrate)

πgc = 29

πbs = 0 (unless pathologic albumin filtration)

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12
Q

Normal GFR

in mL/min

A

125 mL/min

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13
Q

Effect of NE on renal arteries and GFR

A

constricts both afferent and efferent arterioles

overall decrease in GFR due to decreased blood flow

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14
Q

Effect of angiotensin II on renal arteries and GFR

A

preferentially constricts efferent arteriole

increased GFR

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15
Q

Effect of prostaglandins on renal arteries and GFR

A

dilation of afferent

increased GFR

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16
Q

How do COX inhibitors affect renal arteries?

A

decrease PG synthesis

decreased afferent dilation

increased afferent vasoconstriction

17
Q

Peritubular capillaries arise from…

A

efferent arterioles

18
Q

What is the equation used to calculate GFR?

A

GFR x [Xp] = UFR x [Xu]

[Xp] = concentration of X in plasma

UFR = urine filtration/formation rate

[Xu] = concentration of X in urine

19
Q

In what clinical circumstance is creatinine clearance absolutely a poor test choice?

A

catabolic state

serum creatinine is not stable

20
Q

2 reasons why, even when you do the test perfectly, measuring a 24 hr creatinine collection is not a good test

A

10-40% of creatinine is secreted (not filtered)

(and we want to measure GFR–glomerular FILTRATION rate)

creatinine is synthesized at variable rates depending on moment to moment metabolic changes

21
Q

How can 24 hr urine creatinine collection be misleading in early stages of decreased GFR?

A

creatinine is secreted

this occurs after filtration

since creatinine is secreted out of the kidney instead of filtered out, this is not a good test