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block 5 Anna > block 5 lecture 5 bone metabolism > Flashcards

block 5 lecture 5 bone metabolism Flashcards

1
Q

what percentage is organic bone material?

A

40%

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2
Q

what percentage is inorganic bone material?

A

60%

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3
Q

what is the organic materials of bone?

A

type 1 collagen and non-collagenous protein

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4
Q

what is the inorganic portion of bone?

A

calcium hydroxyapatite

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5
Q

what is trabecula bone?

A

cancllous and spongy bone

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6
Q

what are osteoclasts?

A

multi nucleated cells formed from many monocytes

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7
Q

what can increase the resorption of bone by an osteoclast?

A

bigger osteoclasts perform more aggressive resorption of bone

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8
Q

how do osteoclasts adhere to the bone matrix?

A

by forming lipid like adhesions and express strong intergrin interactions

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9
Q

what do osteoclasts do?

A

secrete enzymes and acids to degrade matrix

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10
Q

what happens to degraded bone material by osteoclasts?

A

shoots up through apical membrane and removed from the cell

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11
Q

what are the osteoclast resorption pits called?

A

howships lacuna

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12
Q

what are osteoblats?

A

mononucleated stromal cells

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13
Q

what do osteoblasts come from?

A

mesenchymal cells

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14
Q

what do osteoblasts do?

A

mineralize bone matrix to replace removed bone

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15
Q

what do osteoblasts form into?

A

osteocytes

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16
Q

what do the extesions of osteocytes make connections with?

A

the bones surface and other osteocytes

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17
Q

what do the processes of osteocytes act as?

A

mechnosensors

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18
Q

hat stops osteoclasts resorbing?

A

reversal stage

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19
Q

what is the matrix that osteoblasts lay down?

A

type 1 collagen and non colagenous protein

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20
Q

what is the bone matrix called when it is initially laid down?

A

osteoid

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21
Q

what are some signals involved in bone growth?

A

parathyroid hormine, vitamin D, calcitonin, growth hormone, growth factors, oestrogen, cytokines

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22
Q

what is the calcuim resevoir?

A

skeleton

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23
Q

what are the three fractions of calcium in serum?

A

ionised calcium, protein bound calcium and complexed calcium

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24
Q

what is Ca2+ maintained by?

A

PTH, Vitamin D, cacitonin

25
Q

where do you find phsphate?

A

skeleton and extracellular fluid

26
Q

what are the three fractions of phsophate in serum/

A

ionised phosphate

protein bound phophate and complexed

27
Q

what is phsphate metabolism regulated by?

A

PTH

28
Q

where can you recieve vitamin D?

A

in the skin, digestion

29
Q

in the skin how is vitamin D procuced?

A

7-dehydrocholesterol is converted by UV light to vitamin D

30
Q

how is vitamin D activated?

A

2 rounds of hydroxylation

31
Q

where does the first hydroxylation of vitamin D occur?

A

liver

32
Q

where does the second hydroxylation of vitamin D occur?

A

kidney

33
Q

what type of vitamin D is responsible for most biological mechanisms?

A

principle hormonal form

34
Q

what is the production of vitamin D regulated by?

A

PTH

35
Q

what is the production of vitamin D inhibited by?

A

elevated serum calcium or phosphate

36
Q

what doe vitamin D do?

A

increases calcium and phosphate absorption from intestines
mobilised calcium and phophate from bone
induces marrow monocytes to increase production of osteoclasts to promote resorption

37
Q

what seceretes PTH?

A

parathyroid gland

38
Q

what can PTH stimulate?

A

osteoclast resroption
decresases renal calcium secretion
increases renal production of vitamin D

39
Q

what is parathyroid hormone related protein produced by?

A

normal and malignant cells

40
Q

what is PTHrP required for?

A

development, regulator of proliferation and mineralisation of chondrocytes

41
Q

what s calcitonin?

A

small poly peptide

42
Q

what releases calcitonin?

A

parafollicular cells of the thyroid

43
Q

what induces the release of calcitonin?

A

high plasma calcium levels

44
Q

what does calcitonin do?

A

reduces bone resorption by activating calcitonin receptors expressed by osteoclasts

45
Q

physiology of calcium metabolism to increase?

A

low calcium in circulation is detected by parathyroid gland, PTH is secreted, PTH and vitamin D increases the mobilisation of Ca into circulation

46
Q

physiology of calcium metabolism to decrease?

A

calcium is detected by thyroid C cells, which increases the secretion of calcitonin, which targets osteoclats to limit resrption and decrease calcium in circulation

47
Q

how does oestrogen affect bone metabolism?

A

reduce resorption by inhibiting osteoclastogenesis and inhibiting osteoclast function

48
Q

how does androgens affect bone metabolism?

A

low levels means low bone density in men

they target osteoclasts

49
Q

what are the causes of hypercalcium?

A

primary hyperthyroidism, malignancy, immobalisation, vitamin D toxicity

50
Q

what is primary hyperthyroidism?

A

excessive secretion of PTH

51
Q

what causes primary hyperthyroidism?

A

solitary adenoma of parathyroid glands

52
Q

what are the symptoms of primary hyperthyroidism?

A

excessive skeletal erosion, kidney stones

53
Q

causes of hypocalcemia?

A

renal failure, vitamin D defficiency, prematurity (immture vitamin D metabolism, immature parathyroid gland)

54
Q

what is osteomalacia caused by?

A

vit D defficiency, malabsorption, renal disease, lack of sunlight, anticonvulsants inhibit vitamin D synthesis

55
Q

osteomalacia symptoms?

A

bone pain around hips, muscle weakness, alavated alkaline phosphatase levels, decreased mineralisation, long bones bowing

56
Q

what is osteoporosis?

A

net loss of bone mass and decreasd bone mineral density

57
Q

in what type of person is osteoporosis common?

A

post menopausal woman, elderly, inactive

58
Q

treatment of osteoporosis?

A

calcium supplementation, hormone replacement therapy, bisphosphates, calcitonin, selective estrogen receptor modulators

block 5 Anna (16 decks)

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