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Renal > Renal Physiology VIII > Flashcards

Renal Physiology VIII Flashcards

1
Q

The function of Calcitriol is to maintain plasma levels of

A

Ca2+ and PO4

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2
Q

To accomplish this, calcitriol targets the renal tubules

and does which two things?

A
  1. ) Stimulates Ca2+ reabsorption

2. ) Blocks PO4 excretion

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3
Q

Calcitriol augments PTH-dependent Ca2+ reabsorption in the

A

Distal nephron

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4
Q

A powerful stimulant of Ca2+ and PO4 absorption from the small intestine (CaHPO4)

A

Calcitriol

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5
Q

In addition, Calcitriol induces Ca2+ and PO4 reabsorption from

A

Bone

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6
Q

During renal failure, the lack of calcitriol may play into the condition of

A

Secondary hyperparathyroidism

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7
Q

The overwhelming majority (approximately 99%) of body Ca2+ stores are housed within

A

Bone

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8
Q

There is a modicum of Ca2+ existing predominantly in bound form within the

A

ICF and ECF

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9
Q

Upon filtration from the glomeruli, Ca2+ reabsorption from the renal tubules follows the same general pattern as that of

A

Na+

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10
Q

The vast majority of the filtered load of Ca2+ is reabsorbed from the

A

Proximal tubule

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11
Q

Within the proximal tubule, this process is coupled to

A

Na+ and H2O reabsorption

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12
Q

However, Ca2+ moves mainly via the

A

Paracellular route

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13
Q

Within the TAL, Ca2+ reabsortion is again coupled to Na+ through the membrane potential gradients that are generated by

A

NKCC

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14
Q

Thus loop diuretics that block Na+ reabsorption also impair Ca2+ reabsorption from the

A

TAL

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15
Q

Within the distal tubule, Ca2+ reabsorption is stimulated by PTH and augmented by

A

Calcitriol

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16
Q

Hence, elevated PTH will induce

A

Hypocalciuria

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17
Q

Promote Ca2+ reabsorption from the distal tubule

A

Thiazide diuretics

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18
Q

To summarize, in response to depressed blood [Ca2+], PTH is secreted by the parathyroid glands in order to do what two things?

A
  1. ) Mobilize Ca2+ stores form bone

2. ) Thwart Ca2+ excretion by promoting reabsorption

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19
Q

Targets the proximal tubule to impair PO4 reabsorption and facilitates Ca2+ reabsorption from the distal tubules

A

PTH

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20
Q

In response to a PTH challenge, what would happen to the urinary concentrations of PO4 and Ca2+

A

Urine [PO4] would increase and urine [Ca2+] would decrease

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21
Q

Secondary hyperparathyroidism is known as

A

High bone turnover renal osteodystrophy

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22
Q

During chronic renal disease, Ca2+ reabsorption from the tubules is impaired; this results in

A

Hypocalcemia

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23
Q

Recall that hypocalcemia is the predominant stimulus for

A

PTH secretion

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24
Q

Since calcitriol is also produced within the kidney, chronic renal disease results in

A

Impaired calcitriol synthesis

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25
Q

Without calcitriol, Ca2+ reabsorption from the kidney and GI tract is

A

Blunted (exacerbates hypocalcemia)

26
Q

Recall that calcitriol can block PTH secretion; therefore, diminished calcitriol production can exacerbate

A

Hyperparathyroidism

27
Q

Finally, as renal function is lost, we see the retention of

A

PO4

28
Q

Can directly induce hypocalcemia and has been shown to cause parathyroid hyperplasia

A

Hyperphosphatemia

29
Q

Note that extra-skeletal calcifications (metastatic calcification) may occur within the

A

Heart, skeletal muscle, lungs, and large blood vessels

30
Q

Myopathy and severe muscle weakness often occur with

A

Advanced renal failure

31
Q

A condition of inadequate production of, or resistance to PTH

A

Hypoparathyroidism

32
Q

As has been discussed, within the kidney PTH stimulates the production of calcitriol as well as the
reabsorption of Ca2+ from the

A

Distal nephron (more specifically the distal convoluted tubule)

33
Q

Clinical signs of hypoparathyroidism are

A

Hypocalcemia, hyperphosphatemia, and low urinary Ca2+

34
Q

In hypoparathyroidism, we see a disruption in calcitriol production, this leads to which 2 tings?

A
  1. ) Reduction in the ability to absorb dietary Ca2+ in small intestines
  2. ) Reabsorption of Ca2+ in DCT is prevented
35
Q

Maintenance treatment of hypoparathyroidism involves the use of a form of

-goal is to restore serum Ca2+ to just below normal

A

Vitamin D

36
Q

Why do we want to restore serum Ca2+ to just below normal levels when treating hypoparathyroidism?

A

Prevents symptoms of hypocalcemia while avoiding potential complications of elevated serum Ca2+

37
Q

Since PTH enables the reabsorption of Ca2+ from the distal nephron, low-normal serum Ca2+ must be maintained in order to prevent

A

Hypercalciuria and the resultant nephrolithiasis

38
Q

The kidney can

  1. ) Concentrate urine approximately
  2. ) Dilute urine approximately
A
  1. ) 4-fold

2. ) 10-fold

39
Q

The kindeys concentrating urine maintains body free H2O and is called

A

NEgtive free clearance

40
Q

The dilution of urine eliminates body free H2O and is called

A

Positive free H2O

41
Q

This process relies upon the

A

Countercurrent multiplier mechanism

42
Q

A key structure because of its ability to balance the concentrations of lumenal versus medullary interstitial NaCl and urea: the osmotic gradient

A

The loop of Henle

43
Q

Can the loop of Henle maintain the necessary osmotic gradients without help?

A

No

44
Q

A microvascular network that is intertwined among the loop of Henle

A

Vasa recta

45
Q

Establishes the so called counter-current exchange mechanism that maintains the hypertonicity of the medullary interstitium

A

Vasa Recta

46
Q

The vasa recta recycles NaCl, H2O, and a modicum of urea from the medullary interstitium back into

A

Systemic Circulation

47
Q

What are the three key properties of the vasa recta?

A
  1. ) It’s looped structure
  2. ) Its relatively low blood flow
  3. ) Its inability to perform active transport
48
Q

As blood descends the vasa, H2O loss from the plasma is initially

A

Robust

49
Q

H2O loss then declines precipitously toward the

A

Deep Medullary Zone

50
Q

Gradually increases from the more superficial to deep medullary zones

A

The influx of both NaCl and urea

51
Q

The diffusion of H2O and solutes occurs because of the medullary interstitial osmotic gradient that is supported by the

A

Nephron (counter-current multiplier)

52
Q

As blood ascends the vasa, solute loss (filtration) from the blood decreases because of the

A

Interstitial osmotic gradient

53
Q

However, as blood ascends the vasa, we see the promotion of

A

H2O reabsorption from the interstitium

54
Q

Does the blood leaving the vasa have more or less H2O and solutes than the blood that entered?

A

More (especially NaCl)

55
Q

Through this mechanism with the vasa recta, NaCl is translocated from the interstitium, back into

A

Systemic circulation

56
Q

The functional nephron operates as two looped tubes flowing in

A

Parallel

57
Q

The delivery system is the selectively permeable

A

Nephron proper (proximal tubule)

58
Q

Receives H2O, NaCl, K+, urea, etc. (as filtrate from glomerular blood); most of which is reabsorbed into the interstitium BECAUSE the interstitium contains osmotic gradients

A

Proximal Tubule

59
Q

Assists in maintaining the interstitial osmotic gradients by recycling H2O, NaCl, etc. back into systemic circulation

A

Vasa Recta

60
Q

Recall that changes in renal perfusion (i.e. renal BP) represent an immediate and profound signal to trigger alterations in renal

A

H2O and Na+ Handling

Renal (10 decks)

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