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ILA > Osteoporosis > Flashcards

Osteoporosis Flashcards

1
Q

What is bone made of?

A

Hydroxyapatite crystals
Collagen

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2
Q

Function bone? (2)

A

Shape and support
Storage calcium and phosphate

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3
Q

State 3 main types cell in bone?

A

Osteoblasts- build bone- osteoid
Osteoclasts- digest bone- remodel
Osteocytes- osteoblasts trapped in bone- regulate mineral dep

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4
Q

What type of collagen is bone?

A

Type 1

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5
Q

What are 2 types of mature bone?

A

Compact (lamellar)- replaces woven bone
Spongy (trabecular

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6
Q

What is first bone laid down?
Property?

A

Immature (woven) bone
Matrix- osteoid not mineralised
Irregular arranged

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7
Q

What is split between organic and inorganic in bone matrix?

A

40% organic
60% inorganic

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8
Q

What is bone made of?

A

Organic
Collagen- type 1- tensile strength
Proteoglycans- compressive strength
Matrix proteins- promote bone formation and bone min.

Inorganic
Calcium hydroxyapatite- compressive strength

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8
Q

What is bone made of?

A

Organic
Collagen- type 1- tensile strength
Proteoglycans- compressive strength
Matrix proteins- promote bone formation and bone min.

Inorganic
Calcium hydroxyapatite- compressive strength

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9
Q

What is origin of osteocytes?

A

Mesenchymal

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10
Q

Osteoclast mono or multinucleated?

A

Multinucleated

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11
Q

Outline how bone remodelled?

A

Activation
Pre-osteoclasts attracted to remodelling sites- activated by RANK ligand produced by osteoblasts
Osteoclasts form

Resorption
Osteoclasts gif cavity (resorption pit) in spongy bone- release acids/cathespin K
Calcium released blood

Reversal
Mesenchymal stem cells differentiate into pre-osteoblasts

Formation
Preosteoblasts mature into osteoblasts at surface pit
Release osteoid at site- form soft, non-mineralised matrix
New matrix mineralised- calcium and phosphorus

Quiescence
Site remains dormant
Osteoprotegerin mop up RANK ligand prevent unnecessary remodelling

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12
Q

What activates osteoclasts?
What prod it?

A

RANK ligand- prod osteoblasts

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13
Q

What inhibits RANK ligand?
What prod it?

A

Osteoprotegerin
Osteoblasts

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14
Q

Function Rank ligand?

A

Produced osteoblasts
Stimulate osteoclast bone resorption

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15
Q

Function OPG?

A

Inhibit osteoclast differentiation

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16
Q

Does osteoclast inhibit or increase bone resorption?

A

Inhibit

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17
Q

Name 2 things decrease bone resorption?

A

OPG
Calcitonin

18
Q

Name two things stimulate osteoclast activation?

A

RankL
PTH- stimulate adenyl cyclase- stimulate RankL prod

19
Q

State 4 steps of fracture healing?

A

1) Haematoma formation
2) Bone generation- fibrocartilaginous callus formed
3) Bony callus formation
4) Bone remodelling

20
Q

Explain fracture healing?

A

1) Haematoma formation
Blood vessels in broken bone tear and haemorrage
Clotted blood- haematoma at break site
Clotting process
Bone cells deprived nutrients die- osteocytes

2) Bone Generation - fibrocartilaginous callus formed
Capillaries grow- dead cells clear
Fibroblasts and osteoblasts start reform bone
Fibroblasts- collagen fibres
Osteoblasts- spongy bone (osteoid)
Fibrocartilaginous callus- hyaline and fibrocartilage

3) Bony callus formation
Fibrocartilaginous callus converted into bony callus
Spongy bone takes 2 months to join
Non-union if no healing in 26 weeks

4) Bone remodelling
Bony callus remodelled osteoclasts and osteoblasts
Simple woven to lamellar
Compact bone added

21
Q

State 3 bone diseases?

A

Osteoporosis
Osteopenia
Osteomalacia

22
Q

Define osteoporosis?

A

Bone brittle and fragile- loss tissue and reduced mineralisation
Increased resorption compared formation
Bone mineral density of -2.5 SD compared reference

23
Q

Define osteopenia?

A

Protein and mineral content decreased
BMD of -1
Rickets

24
Q

Define osteomalacia?

A

Softening bone- mineralisation doesn’t occur
Deficiency vit D/calcium

25
Q

Function vitamin D?

A

Aid absorption calcium

26
Q

State uses calcium?

A

Neurotransmission
Muscle contraction
Hormone secretion
Clotting cascade

27
Q

What are 3 molecules regulate amount calcium?
Where synthesis/secrete

A

Calcitriol (vit D)- synthesis kidney
PTH- parathyroid glands
Calcitonin- thyroid glands

28
Q

Function vitamin D?

A

Increase intestinal absorption calcium

29
Q

Explain vit D synthesis?

A

1) 7-dehydrocholesterol converted into cholecalciferol (vitamin-D3) under influence UV radiation
2) In liver cholecalciferol converted 25-hydroxyvitaminD by 25-hydroxylase
3) In kidney 1a-hydroxlase converts 25-hydroxyvitaminD into 1,25-dihydroxyvitaminD (calcitriol)
Metabolically active

30
Q

What occurs once calcitriol synthesised?

A

Released bloodstream
Stimulate intestinal epithelial cells increase synthesis calbindin D proteins
Calbindin-D proteins facilitate transport calcium from intestinal brush border to basolateral membrane- released into blood
Intestinal absorption calcium increased

31
Q

Where does calcium exist in body?

A

99% bone
0.99 blood
0.01 cells

32
Q

How much calcium?

A

1200g

33
Q

What form does calcium exist in blood (3)?

A

Free ionised- diffusible, biologically active
Bound anions- diffusable, not biologically active
Bound proteins- albumin- not diffusable, not biologically active

34
Q

What protein does calcium normally bind to?

A

Albumin

35
Q

What occurs if low calcium in blood?

A

Reduce inhibition of chief cells in PTH gland
Additional PTH secreted
Raise calcium lvls

36
Q

What cells secrete PTH?

A

Chief cells

37
Q

How does PTH raise blood calcium lvls?

A

Increase bond resorption- PTH bind osteoblast- increase expression RANKL- stimulate preosteoclast to osteoclast- reabsorb bond and release calcium

Increase renal reabsorption calcium- PTH cause expression channels in DCT- increase resorption calcium- increase excretion phosphate

Increase synthesis calcitriol- in kidney PTH increases expression 1a Hydroxylase- catalyse conversion inactive 25-hydroxycholecalciferol into calcitriol

38
Q

What inhibits secretion PTH from chief cells in parathyroid gland?
Why?

A

PTH and calcitriol inhibit secretion PTH from parathyroid gland
Negative feedback loop- ensure blood calcium lvls don’t rese past normal range

39
Q

What occurs if calcium in blood rises above normal range?

A

Parafollicular cells in thyroid gland secrete calcitonin
Calcitonin inhibit osteoclasts- reduce bone resorption

40
Q

What decrease calcium lvls? How?

A

Calcitonin- inhibit osteoclasts- decrease bone resorption

41
Q

What are main constituents of hydroxyapatite?

A

Calcium
Phosphate

42
Q

What occurs if calcium reabsorption increases?

A

Phosphorous excretion
Inverse relationship

ILA (12 decks)

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