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Musculoskeletal system > Bone formation and absorption > Flashcards

Bone formation and absorption Flashcards

1
Q

Why are bones constantly remodelled?

A

Repairs breaks/injuries/microfractures

Change in response to stresses like exercise

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2
Q

Flow chart of the process of remodelling bone?

A

Quiescence - resorption - reversal - formation - mineralisation - quiescence

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3
Q

What happens during quiescence?

A

Nothing is occurring

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4
Q

What happens during the reversal stage of making bone?

A

Macrophages clear up debris left behind by osteoclastic activity

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5
Q

What happens during the formation stage of forming bone?

A

Osteoblasts lay down bone tissue

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6
Q

Where does bone growth occur?

A

At the epiphyseal plate

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7
Q

Which type of cell divides to bring about bone growth?

A

Chondrocytes

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8
Q

How do bones grow?

A

Chondrocytes (cartilage) replicate, die and are replaced by calcified cartilage and bone

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9
Q

What stages does cartilage go through at the epiphyseal plate?

A 
Resting cartilage
Proliferating cartilage
Hypertrophic cartilage
Cell death
Calcified cartilage
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10
Q

What happens to epiphyseal cartilage in adults?

A

It is replaced by bone, leaving the epiphyseal line

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11
Q

How does bone thicken?

A

Osteoblasts lay down bone matrix
Results in groove forming alongside periosteal blood vessel
Forms tunnel containing new vessel
Remodelled and forms new osteon
New outer circumferential lamellae laid down

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12
Q

Factors affecting bone growth

A

Dietary intake - calcium/phosphate/vitamin D

Hormones - growth hormone/insulin/PTH/calcitonin

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13
Q

Where does bone thickening occur?

A

At the bone surface

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14
Q

What does the embryonic skeleton comprised of?

A

Mesenchyme in the general shape of a skeleton

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15
Q

What are the two patterns of bone formation?

A

Intramembranous ossification

Endochondral ossification

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16
Q

What is intramembranous ossification?

A

Forms flat bones of skull/mandible/clavicle within membrane

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17
Q

What is endochondral ossification?

A

Cartilage is replaced by bone

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18
Q

Describe the process of intramembranous ossification

A

Mesenchyme cells cluster together and turn into osteoprogenitor cells which turn into osteoblasts
This creates ossification centres (bone and bone matrix is laid down)
Osteoblasts form osteocytes, causing calcification
Trabeculae (spongy bone) begins to form
Periosteum develops on outside

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19
Q

What type of cells are osteoprogenitor cells?

A

Stem cells

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20
Q

Describe the process of endochondral ossification

A

Mesenchyme forms bone shape
Develops into chondroblasts which secrete cartilage ECM
This produces a hyaline cartilage model, which grows
Ossification centres (turn cartilage to bone) form
Secondary ossification centres develop
Articular cartilage and epiphyseal plate form

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21
Q

Describe the process of fracture repair

A

1) Hematoma stage - haemorrhage and clot formation occurs within a few days
2) Inflammatory stage - inflammatory cells appear, organisation and resorption of clot, soft callus forms
3) Hard callus - bony callus grows and bridges fracture site, trabecular bone laid down by osteocytes
4) Remodelling - bone is reorganised and original structures are restored

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22
Q

Flow chart of fracture repair

A

Hematoma - inflammatory stage - hard callus - remodelling

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23
Q

What factors regulate bone growth?

A

Diet, physical activity, hormones, genetics

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24
Q

What causes bones to be flexible?

A

Collagen

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25
Q

What causes bones to be rigid?

A

Mineral salts

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26
Q

Where does the growth of bone (length) occur?

A

Epiphyseal plate

27
Q

Where does thickening of bone occur?

A

External surface

28
Q

What do calcium and phosphate do to contribute to bone health?

A

Make bone ECM hard

29
Q

What does magnesium do to contribute to bone health?

A

Helps form bone ECM

30
Q

What does fluoride do to contribute to bone health?

A

Strengthen bone ECM

31
Q

What does manganese do to contribute to bone health?

A

Activates enzymes to synthesise ECM

32
Q

What does vitamin A do to contribute to bone health?

A

Stimulates osteoblasts

33
Q

What does vitamin C do to contribute to bone health?

A

Synthesises collagen

34
Q

What does vitamin D do to contribute to bone health?

A

Helps absorb calcium in gut

35
Q

What do vitamins K and B12 do to contribute to bone health?

A

Synthesise bone protein

36
Q

What is the active form of vitamin D?

A

1,25(OH)2D

37
Q

What are the two routes that can create vitamin D?

A

Sunlight - skin - 7-dehydroxycholesterol

Food - vit D - liver - kidney

38
Q

What is a deficiency of vitamin D called?

A

Rickets

39
Q

Characteristics of rickets

A

Bone matrix fails to calcify
Weight-bearing bones bend
Deformed pelvis and rib cage

40
Q

What is osteomalacia?

A

Adult rickets

41
Q

Characteristics of osteomalacia?

A

Lack of vitamin D/calcium or renal disfunction
Poorly calcified bones
Soft bones = more frequent fractures
Bone pain

42
Q

Why is exercise important for healthy bones?

A

Mechanical stress causes increases osteoblast activity, which means increased deposition of bone
No stress = more bone resorption than formation

43
Q

When will bone homeostasis be achieved?

A

When osteoclasts (bone resorption) = osteoblasts (bone formation)

44
Q

How are trabecular arranged to best support bones?

A

Arranged along stress lines which absorb compressive loads

They remodel in response to activity changes

45
Q

What does growth hormone do?

A

Stimulates osteoblasts to form bone and increase bone mass

Stimulates chondrocytes to increase rate of cell differentiation

46
Q

Function of chondrocytes

A

Secrete extracellular matrix

47
Q

What are the two ways pituitary gigantism can occur?

A

Too much GH in childhood

Lack of oestrogen closes epiphyseal plates

48
Q

What is osteogenesis imperfecta?

A

A genetic disorder that causes weak bones that break easily

49
Q

What causes osteogenesis imperfecta?

A

Defects in collagen synthesis

50
Q

What is osteogenesis deformans?

A

Defect in bone remodelling - osteoclasts absorb bone quicker, osteoblasts produce bone quicker
The new bone is longer and weaker

51
Q

Which aspects of bone formation are of particular interest to forensics and anthropology?

A

Ossification centres, the time of appearance and the rate at which they grow

52
Q

How is bone age measured?

A

Assessing expected growth using x-ray images

53
Q

Which condition is caused by the over-secretion of GH in adulthood?

A

Acromegaly

54
Q

Where is thyroid hormone produced?

A

The thyroid

55
Q

What does thyroid hormone do?

A

Stimulates osteoblasts to promote bone growth

56
Q

Where is insulin secreted?

A

Pancreas

57
Q

What does insulin do to bones?

A

Increases synthesis of bone proteins to promote bone growth

58
Q

Example of androgen

A

Testosterone

59
Q

What do androgens do?

A

Responsible for bone strength in males

60
Q

Why are gonadal steroids important for bones?

A

Important in regulating bone growth and development of peak bone mass

61
Q

Why is oestrogen important for bone health?

A

Regulates bone formation and re-absorption

Shuts down growth at epiphyseal plate

62
Q

What is osteoporosis?

A

Osteoclasts > osteoblasts
Bone mass and amount of collagen decreases
Haversian canals emerge and are filled with adipose tissue

63
Q

Why does bone heal more rapidly than cartilage?

A

It has a better blood supply

Musculoskeletal system (24 decks)

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