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Unit 2 Phys II > L19+20: Calcium and Phosphate > Flashcards

L19+20: Calcium and Phosphate Flashcards

1
Q

most calcium is

A

found in crystalline form in bone

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2
Q

net daily absorption/excretion of calcium

A

200 mg

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3
Q

free+bound calcium in blood

A

10 mg

half free, half bound

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4
Q

net daily absorption/excretion of phosphate

A

650 mg

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5
Q

Most phosphate is found in

A

bones (85%)

muscle (15%)

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6
Q

Phosphate functions

A
  1. fuel provision, high energy transfer/storage
  2. cofactors (NAD)
  3. second messengers
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7
Q

regulate calcium and phosphate levels in blod

A

PTH

vitamin D

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8
Q

trigger for PTH release

A

hypocalcium

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9
Q

PTH is released from

A

chief cells of parathyroid glands

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10
Q

PTH effects on bone:

A

activates osteoclasts: bone breakdown: calcium and phosphate ions released into blood

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11
Q

PTH effects on intestine:

A

increased calcium absorption

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12
Q

PTH effects on kidney:

A
  1. promotes activation of vitamin D
  2. increases calcium reabsorption
  3. promotes excretion of phosphate
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13
Q

mineralized bone

A

hydroxyapatite: Ca10(PO4)6(OH)2

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14
Q

stable pool

A

slow resorption, contains mineralized bone

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15
Q

Labile pool

A

fast osteolytic osteolysis, contains bone fluid of amorphous crystals

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16
Q

amorphous crystals

A

CaHPO4:2H2O

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17
Q

separates the bone from plasma within canals

A

osteocytic-osteoblastic bone membrane

-formed by projection from osteocytes

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18
Q

osteocytic-osteoblastic bone membrane function

A

large surface area: small movement of calcium across the membrane=large influx between bone fluid and plasma

19
Q

what moves calcium across the osteocytic-osteoblastic bone membrane

A

fast exchange: PTH-activated calcium pumps

slow exchange: PTH-induced dissolution of bone

20
Q

elimination of PO4 in urine leads to increased

A

urine cAMP

21
Q

how does PTH activate vitamin D

A

stimulates 1-alpha hydroxylase activity

22
Q

sunlight converts

A

7-dehydrocholesterol to vitamin D3

23
Q

vitamin D3 activation

A

Liver:
adds OH to C25
25-hydroxyvitamin D3

24
Q

25-hydroxyvitamin D3 activation

A

Kidney:
add OH to C1
1,25-dihydroxyvitamin D3

25
Q

25-hydroxyvitamin D3 inactivation

A

add OH to C24

24,25-dihydroxyvitamin D3

26
Q

active form of vitamin D

A

1,25-dihydroxyvitamin D3

27
Q

vitamin D action on bone

A

synergistic with PTH

resorption: mobilization of calcium and phosphate

28
Q

vitamin D action on kidenys

A

promotes calcium reabsorption at distal tubule

promotes phosphate reabsorption at proximal tubule

29
Q

vitamin D action on small intestine

A

increases expression of calbinding

30
Q

calbindin

A

in small intestine cells

binds calcium, which is then pumped into bloodstream by Ca-ATPase on basolateral membrane

31
Q

stimulus for calcitonin release

A

high plasma calcium

32
Q

Calcitonin actions

A
  1. inhibits bone resorption of Ca and PO4

2. inhibits renal reabsorption of Ca and PO4

33
Q

Calcitonin effect on intestines

A

none

34
Q

Primary hyperparathyroidism

A

causes by PTH-secreting adenoma

  1. hypercalcemia, hypophosphatemia
  2. urine: increased PO4, cAMP, hypercalciuria

osteorporosis, osteomalacia, kidney stones, muscle weakness and decresed muscle excitability

35
Q

Hypoparathyroidism

A

caused by surgery
Low PTH, hypocalcemia, hyperphosphatemia

Hypocalcemia: teatany, hyperreflexia, spontaneous twitching, muscle cramps, convulsions

36
Q

Positive trousseau’s sign

A

flexed hand?

due to low calcium levels in hypoparathyroidism

37
Q

Humoral hypercalcemia of malignancy

A

PTH-related peptide (PTH-rp) secreted
effects of excess PTH
PTH levels are low due to hypercalcemia

38
Q

Pseudohypoparathyroidism aka

A

albright’s hereditary osteodystrophy

39
Q

Pseudohypoparathyroidism

A

autosomal dominant disorder
Defective Gs is PTH resistant
Elevated PTH, hypocalcemia, hyperphosphatemia

Short, short neck, obese, shortened metatarsals and metacarpals

40
Q

vitamin D deficiency in childhood

A

rickets

41
Q

vitamin D deficiency in adulthoood

A

osteomalacia

usually dietary deficiency or intestinal surgery, renal failure, celiac disease

42
Q

Rickets

A

insufficient vitamin D to mineralize growing bone
growth failure, skeletal abnormalities, tetany, weakness, fractures
hypocalcemia
elevated PTH

43
Q

Osteomalacia

A

softened, weakened bones, frequent fractues

hypocalcemia, tetany

Unit 2 Phys II (11 decks)

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