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RAD 415 > what is the function of bone > Flashcards

what is the function of bone Flashcards

1
Q

what are the 3 main functions of bone

A

store of calcium

production of red blood cells/platelets

maturation with blood cells

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2
Q

what is the predominant gelatinous fluid in bone

A

ground substance (amorphous gelatinous material. It is transparent, colourless, and fills the spaces between fibres and cells)

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3
Q

what other substance holds a high proportion of bone formation

A

collagen (collagen fibres)

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4
Q

what is difference about collagen fibres in bone

A

they are calcified under physiological conditions

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5
Q

define osteoid

A

pre mineralisation cartilaginous tissue

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6
Q

what makes the extracellular matrix in bone strong

A

formation of hydroxyapatite crystals from calcium and phosphate

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7
Q

what prevents the formation of hydroxyapatite crystals in other tissues (despite them having normal levels of phosphate and calcium)

A

they have an inhibitor called pyrophosphate

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8
Q

what can happen if a tissue fails to produce pyrophosphate

A

degenerating tissues that fail to make this can become calcified

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9
Q

what might cause tissue calcification

A

under physiological conditions alkaline phosphates remove pryophosphate allowing bone mineralisation

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10
Q

what is extracellular matrix (similar to cartilage) formed by

A

osteoblasts

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11
Q

how do osteoblasts create the extracellular matrix

A

by secreting collagen and ground substance

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12
Q

what do osteoblasts create when they reach a quiescent state (dormant)

A

osteocytes

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13
Q

how are osteoblasts simulated

A

by compressive forces

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14
Q

why might astronauts experience osteoperosis

A

due to lack of compressive forces on bones

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15
Q

what component can break down bone

A

osteoclasts

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16
Q

what property do osteoclasts have in common with monosytes

A

contain lysosomes that can degrade tissue

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17
Q

what 2 functions do osteoblasts hold besides formation of matrix?

A
  • hold precursors with PTH receptors that secret RANK ligand. RANKL stimulates differentiation of immature osteoclasts into active cells
  • produce osteoprotegrin which can block the RANKL receptor and promote bone growth
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18
Q

what are osteoclasts indirectly stimulated by

A

RANK ligand

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19
Q

what drug increases bone density and how

A

bisphosphonates,

they can incorporate well into calcium rich tissue and when taken up by osteoclasts, they can severely reduce osteoclast function.

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20
Q

what are some disadvantages to taking biphosphates to promote bone growth

A

can irritate the stomach and oesophageal lining and increase peptic ulcer risk

21
Q

what does synergistic mean

A

cooperation of 2 substances creates a greater effect than sum of separate effects

22
Q

why is it important to be wary of the medications being taken with biphosphates

A

risk is synergistic

(patients who need biphosphates may have indication for non steroidal anti-inflammatory drugs and or cortisteroid medication - both can affect lining of GI tract

23
Q

what is ostenecrosis

A

a degenerative bone condition characterized by the death of cellular components of the bone secondary to an interruption of the subchondral blood supply

24
Q

why is biphosphate prescribed to patients with poor dentition something to be wary of

A

can cause osteonecrosis of jaw

25
Q

what are the 2 main sources of vitamin d and what type of vitamin d do each provide

A

sun = vitamin d3

fish = vitamin d2

26
Q

what is the process of producing activated vitamin D

A

vitamin d2 and d3 get hydroxylated by the liver and then it gets hydroxylated by the kidney to make activated vitamin D3

27
Q

what happens when the parathyroid gland detects low serum calcium in blood

A
  • parathyroid hormone is secreted (PTH)
  • stimulates bone breakdown released calcium and phosphate into blood
  • PTH release favours calcium reabsorption (from urine) and stimulates phosphate loss/excretion of phosphate
  • PTH also stimulates kidney to activate vitamin D
  • activated vitamin D causes increase absorption of calcium from diet
28
Q

what are Haversian canals in bone

A

tubes which form a network in bone and contain blood vessels.

29
Q

what do the Haversian canals allow in bone

A

vascular and neural connections in bone

30
Q

what can be found around the Haversian canals

A

cone osteocytes and bone tissue forming concentric rings called lamellae

31
Q

what is an osteon

A

unit of tissue forming rings around a canal

32
Q

what is cortical bone

A

harder ‘compact’ bone found towards outer edge

33
Q

describe the structure of inner bone

A

less densely packed, forms a spongy matrix type structure known as spongy/ CANCELLOUS bone

34
Q

what component does the spongy tissue in diaphysis of bone house

A

yellow bone marrow which predominantly produces cells of immune system

35
Q

what component does the spongy tissue in epiphysis house

A

red bone marrow which produces red blood cells (erythrocytes) and platelets

36
Q

what is cancellous bone formed of

A

trabeculae

37
Q

describe process of bone formation

A

form ossification of cartilage
- initially bone is totally cartilaginous structure that ossifies in stages

38
Q

describe ossification in long bones

A

ossification happens at epiphyses before diaphysis

39
Q

explain how bone growth stops when you become an adult

A
  • cartilage at metaphysics keeps producing new cartilage until end of puberty
  • if cartilage production exceeds rate of ossification the bone will continue to grow
  • as growth of cartilage slows the diaphysis and metaphysics fuse and bone growth stops/adult heigh is reached
40
Q

what is the salter-harris classification system

A

a method used to grade fractures that occur in children and involve the growth plate

41
Q

whats the difference between primary and secondary bone healing

A

primary = involves low strain conditions
secondary = higher strain conditions

42
Q

how is a fractured bone healed

A
  1. initially hepatoma is formed
  2. haematoma can organise to form a callus
  3. callus is replaced by spongy ‘cancellous’ bone
  4. bone is reorganised
43
Q

what can failure to heal bone lead to

A

pseudoarthrosis, occurs when bones do not fuse correctly after an injury or surgery

44
Q

how might you be able to diagnose osteoporosis

A
  • DEXA scans measure bone mineral density
  • this can be used with other things to measure a FRAX score which gives the risk of fragility fracture
45
Q

what is osteosarcoma and where in the bone is this typically ound

A
  • tumour arising from osteoblastic precursor
  • found close to metaphysis
46
Q

what is the difference between primary and secondary osteosarcoma

A

primary= in children with no history of bone disease

secondary = in adults with previous history of bone disease (symptoms being pain worsening with excersise)

47
Q

what are 2 types of treatment for osteossarcoma

A
  1. surgery
  2. chemotherapy
48
Q

where can ewings sarcoma typically be found

A

diaphysis of long bones

49
Q
A

RAD 415 (19 decks)

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