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Renal > Renal Function 4 > Flashcards

Renal Function 4 Flashcards

1
Q

Importance of Calcium:

A
  1. stabilizes the excitable cell membrane
  2. 2nd messenger for cell signaling
  3. essential​ for blood clotting

** Tight control of ECF calcium is essential

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2
Q

Importance of phosphate:

A
  1. component of many organic molecules
  2. store and release ATP in bonds
  3. protein phosphorylation control many intracellular processes
  4. urinary buffer

**Tight​ control of phosphate not essential

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3
Q

Mineral homeostasis​:

A
  • dietary intake and absorption
  • distribution within body components (redistributed)
  • excretion (primarily​ by kidney
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4
Q

bone, kidney, and intestine are together regulating?

A

inflow, outflow, and redistribution​ of calcium and phosphate between different body compartments

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5
Q

A physiological​ important component​ of Calcium?

A

Ionized calcium - 50% of Ca in blood
- free form is closely regulated

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6
Q

What affects bound calcium?

A

pH affects the ​amount bound to albumin

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7
Q

What influences complex calcium?

A

plasma phosphate

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8
Q

Where does Ca absorption occue​?

A

upper small intestine
-inefficient process (only 20% absorbed)

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9
Q

What is the calcium binding​ protein in intestinal cells regulated by?

A

Vitamin D3

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10
Q

What happens if a lot of phosphate from the diet binds with calcium?

A

It stops it from being absorbed

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11
Q

Intestinal absorption of Ca is influenced​ by ?

A

active vitamin D

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12
Q

What type of tissue is bone?

A

active - because it remodels

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13
Q

osteclast:​

A

resorb bone - release​ Ca and phosphate

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14
Q

osteoblasts:

A

responsible for new bone formation and its mineralization

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15
Q

bone turnover =

A

balance between resorption and formation

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16
Q

In the Kidney in calcium filtered?

A

Yes - both free and complex Ca is filtered

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17
Q

What % of Ca is reabsorbed in prox​imal tubule (passive reabsorption)?

A

70% -

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18
Q

What type of Ca reabsorption happens in the late distal tubule?

A

active reabsorption regulated by PTH

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19
Q

Does tubular secretion of Ca2+ occur?

A

no

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20
Q

When does uptake of phosphate happen in cells and why?

A

after feeding (insulin) - because insulin stimulates phosphate uptake in order to phosphorylate​ glucose

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21
Q

Phosphate is diet is absorbed by?

A

active transport stimulated by Vitamin​ D3

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22
Q

The more Ca in diet , the more MG, the more multivalent leads to

A

less available phosphate for absorption

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23
Q

What happens to phosphate when calcium is released from bone?

A

phosphate is also released

24
Q

how much phosphate present in plasma is filtered?

A

around 90% - not much protein binding of phosphate

25
Q

Phosphate is actively reabsorbed by?

A

proximal tubule ( Co transport with Na+ which​ is regulated by PTH)

26
Q

phosphate overflow process:

A
  1. Phosphate filtered by the ​glomerulus
  2. reabsorbed by proximal tubule via co-transport
  3. some escapes from reabsorption (overflow) and is excreted
27
Q

What does the rate of phosphate secretion depend on?

A
  1. depends on GFR
  2. It is proportional​ to plasma phosphate
  3. phosphate transporter salurate
28
Q

Where will you see phosphate present in urine:

A

in normal circumstances

29
Q

Excess PTH = __ phosphate

A

less phosphate

30
Q

lack of PTH = __ phosphate

A

more phosphate

31
Q

Is a major INTERCELLULAR cation?

A

magnesium

32
Q

Where is the majority of magnesium present?

A

bone matrix

33
Q

regulation of Mg:

A

not understood

34
Q

Is a major site of Mg absorption​?

A

thick ascending​ loop o

35
Q

___ can increase Mg excretion?

A

Aldosterone

36
Q

hormones involved in calcium balance?

A
  • PTH
  • Active Vitamin D3
  • Calcitonin –> produced by c-cells in thyroid gland
37
Q

hormones involved in phosphate balance?

A
  • FGF-23
  • Hormones regulating calcium also affect phosphate
38
Q

PTH secretion is regulated by?

A

ionized calcium

39
Q

inhibit PTH (negative feedback)

A
  • vitamin D3
  • FGF-23
  • severe hypomagnesium
40
Q

Effects of PTH:

A
  • stimulates Ca2+ and phosphate from bone
  • promotes renal reabsorption of Ca2+ from the distal tubule
  • Promotes renal excretion of phosphate
  • stimulates synthesis of active Vitamin D3- 1,25
  • promotes Mg absorption from loop
41
Q

Whemn PTH is reduced ___ returns calcium to bone?

A

1,25 D3

42
Q

PTH: Bone

A

stimulates release pf Ca and phosphate from bone to ECF

43
Q

PTH: Kidney

A
  • promotes phosphate excretion via urine
  • makes more 1, 25 Vitamin D3
  • reabsorb calcium
44
Q

PTH: ECF

A
  • v1, 25 D3 increases absorption of Ca and phosphate from gut
45
Q

Where is Viatmin D3 obtained?

A

diet or skin

46
Q

25-hydroxylated by?

A

liver (not regulated)

47
Q

1 alpha hydroxylated by?

A

kidney (active)

48
Q

enhances 1 alpha hydroxylated ?

A

PTH

49
Q

inhibits 1 alpha hydroxylated

A

phosphate and FGF-23 may

50
Q

24-hydroxylated by ?

A

kidney (inactive)

51
Q

inhibits 24-hydroxylated:

A
  • PTH
52
Q

enhances 24 hydroxylate?

A

phosphate / FGF-23

53
Q

Calcitronin is secreted by ?

A

C- cells of the ​thyroid gland

54
Q

FGF-23 produced by?

A

osteoblasts and osteocytes in repsonse to an ​increase in ECF phosphate

55
Q

FGF-23 inhibits

A

phosphate entry / lowers phosphate in ECF by:
- inhibiting calcitriol formation ( inhibits PO4 entry in the gut
- inhibits PTH secretion ( inhibits PO4 release from bone)
- inhibits proximal tubular reabsorption of PO4

Renal (5 decks)

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