MS System - Bones Flashcards

Emily

1
Q

What is bone?

A
  • Collagen fibre framework
  • In a mucopolysaccharide-rich gel
  • Hardened by hydroxyapatite crystals
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2
Q

Epiphysis

  • where
  • structure
  • function
A
  • Top of bone
  • Top = articular surface w hyaline cartilage
  • Movement, stability
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3
Q

Diaphysis

  • where
  • structure
  • function
A
  • Middle of bone
  • Outside = compact bone, inside = hollow cylinder (bone marrow)
  • Where blood vessels enter
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4
Q

Metaphysis

  • where
  • structure
  • function
A
  • Between epiphysis & diaphysis
  • Plates of hyaline cartilage
  • Region of growth
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5
Q

Cancellous (trabecular) bone

  • where
  • structure
  • function x2
A
  • Both ends
  • Porous, open structure
  • Supporting strength
  • Site of haemopoiesis
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6
Q

Cortical (compact) bone

  • where
  • structure
  • function
A
  • Outside (forms shaft)
  • Solid, compact
  • stiffness, strength
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7
Q

Periosteum

  • where
  • structure
A
  • Outside of diaphysis

- Compact bone

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8
Q

Trabeculae

A

Laid along lines of stress:

  • Allows distribution of stress
  • High SA for metabolism
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9
Q

Loss of trabecular due to…

A

If bones aren’t stressed –> bones remodel –> lose trabeculae

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10
Q

Haversian Canals

A

Blood vessels along the LONG axis

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11
Q

Volkmann’s Cannals

A

Blood vessels along the PERPENDICULAR axis

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12
Q

Lamellae

  • what
  • where
A
  • Concentric circles around vessels

- Mainly in cortical bone

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13
Q

Lamellae & osteocytes

A

Most cells are in v close contact to blood vessels, BUT osteocytes aren’t –> finger-like projections

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14
Q

Cancellous bone & lamellae

- SO?

A
  • Less lamellar layers
    SO
  • Less dense & coordinated –> weaker
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15
Q

Bone matrix components x3

A
  • Collagen (organised arrangement)
  • Hydroxyapatite
  • Water
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16
Q

What is hydroxyapatite?

A

Precipitated calcium phosphate crystals

17
Q

Osteoblasts

  • function
  • structure
  • extra
A
  • Bone builders
  • Mononucleate
  • Deposit collagen –> then hydroxyapatite
18
Q

Osteoclasts

  • function
  • structure
  • extra
A
  • Bone chewers
  • Multinucleate
  • Reabsorb bone by demineralisation:
    - forms ‘sealing zone’ –> protons & hydrolytic enzymes –> breaks down bone matrix –> releases Ca
19
Q

Osteocytes

  • function x2
  • formed
A
  • Maintain matrix
  • Relatively inactive
  • Osteocytes become entombed in matrix/lacunae
20
Q

Osteoprogenitors

  • where
  • function
A
  • Line bone surface

- Stem cells –> form osteoblasts

21
Q

Formation of woven bone

  • when damaged…
  • then…
  • over time…
A
  • Periosteum = damaged –> sends signals –> increased blood flow, inflammation
  • Callus formation –> osteoblasts form ‘woven bone’ = weak
  • Lamellular bone laid down
22
Q

Lamellular bone = stronger than woven bone as…

A

Woven bone –> collagen fibres = irregular

Lamellular bone –> collagen fibres = in sheets

23
Q

Wolff’s Law

A

Bone adapts to the load under which it is placed

24
Q

Bone remodelling/straightening

A

Side with more pressure remodels more –> bone can straighten

25
Q

Calcitonin

A

Less osteoclast activity –> lower blood Ca levels

26
Q

PTH

Parathyroid hormone

A

More ostoaclast activity –> releases Ca

27
Q

Bone remodelling (4 steps)

A

1) Quite (quiescence)
2) Osteoclasts –> demineralisation
3) Osteoprogenitors –> differentiate to osteoblasts
4) Osteoblasts –> lay down new bone

28
Q

Bone mass & menopause

A

Decreases faster –> as less oestrogen = more bone ‘chewing’

29
Q

Chondroblasts

A

Form cartilage

30
Q

Chondroclasts

A

Remove cartilage

31
Q

Ossification

A

The process where cartilage is replaced by bone

32
Q

Centres of ossification:

  • primary
  • secondary
A
  • Diaphysis

- Epiphysis

33
Q

Epiphyseal plate

  • what
  • where
  • structure
A
  • Growth plate
  • Between epiphysis & diaphysis
  • Made of cartilage
34
Q

Growth stops when…

A

Epiphysis & diaphysis fuse

normally end of puberty

35
Q

Ossification process (5 steps)

A

1) Resting zone
- Chondroblasts lay down cartilage (by epiphysis)
2) Growth zone
- Chondroblasts –> mitosis
3) Hypertrophic zone
- Differentiate –> chondrocytes = swell (increase cytoplasm)
4) Calcification zone
- Swelling –> mineralisation
5) Ossification zone
- Disorganised bone from mineralisation = remodelled