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Z OLD Tissues of the Body > Ossification and Bone Disease > Flashcards

Ossification and Bone Disease Flashcards

1
Q

What does endochondral ossification involve?

A

The replacement of a pre-existing hyaline cartilage template by bone

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2
Q

What is endochondral ossification the mechanism for?

A

The development of most of the bones in the body

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3
Q

Where is endochondral ossification particularly important?

A

Mostly in long bones

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4
Q

Where does endochondral ossification occur?

A

Foetus

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5
Q

What does endochondral ossification in the foetus form?

A

The skeleton

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6
Q

What part of long bones become ossified first?

A

Diaphyses

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7
Q

What is the precursor for most bones?

A

A hyaline cartilage model

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8
Q

What happens in endochondral ossification?

A

Cartilage is mineralised to form bone

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9
Q

What do growing bones have?

A

Growth plates of hyaline cartilage

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10
Q

How long does the femur continue to grow for?

A

Into adulthood

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11
Q

How does the femur continue to grow into adulthood?

A

By continuous production of cartilage

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12
Q

On what side does cartilage change into bone in long bones?

A

Shaft side

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13
Q

What happens after the cessation of long bone growth?

A

The epiphyseal plate disappears

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14
Q

How much bone is present in a 5-6 week old embryo?

A

None- it’s purely the hyaline cartilage model

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15
Q

When does endochondral ossification occur?

A

In a 5-6 week embryo

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16
Q

What happens in a 5-6 week old embryo?

A

A collar of periosteal bone appears in the shaft

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17
Q

What happens in an 8-12 week old fetus?

A
  • The central cartilage calcifies
  • Nutrient artery penetrates
  • Formation of the primary ossification centre
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18
Q

What does the nutrient artery provide?

A

Bone-depositing osteogenic cells

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19
Q

What happens regarding bone development postnatal?

A
  • Medulla becomes calcified bone
  • Cartilage forms epiphyseal growth plates
  • Epiphyses develop secondary centres of ossification
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20
Q

What happens regarding bone development prepubertally?

A

Epiphyses ossify and growth plates continue to move apart

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21
Q

What is the result of the moving apart of the growth plates?

A

Bone lengthening

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22
Q

What happens regarding bone development in a mature adult?

A

NAME?

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23
Q

How does bone increase in length?

A

Endochondral ossification

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24
Q

How does bone increase in girth?

A

Periosteal ossification

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25
Q

What is periosteal ossification?

A

Intramembranous ossification

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26
Q

What extends from the growth plate when a bone is growing?

A

Columns of calcified cartilage

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27
Q

What happens to the columns of calcified cartilage in growing bone?

A

It becomes mineralised

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28
Q

What are the 5 zones of the epiphyseal growth plates?

A
  • Zone of reserve cartilage
  • Zone of proliferation
  • Zone of hypertrophy
  • Zone of calcified cartilage
  • Zone of resorption
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29
Q

What is not happening in the zone of reserve cartilage?

A
  • Cellular proliferation

- Active matrix production

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30
Q

What happens in the zone of proliferation?

A

NAME?

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31
Q

What happens in the zone of hypertrophy?

A

NAME?

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32
Q

What happens in the zone of calcified cartilage?

A

NAME?

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33
Q

What is calcified matrix in direct contact with in the zone of resorption?

A

The marrow cavity

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34
Q

What happens in the zone of resorption?

A

Small blood vessels and connective tissue invade the region occupied by the dying chondrocytes, leaving the calcified cartilage in spicules between them

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35
Q

What happens are the cartilage spicules in the zone of resorption?

A

Bone is laid down

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36
Q

Where does intramembranous ossification take place?

A

Within condensations of mesenchymal tissue

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37
Q

Does intramembranous ossification involve the replacement of a pre-exisiting hyaline cartilage template?

A

No

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38
Q

What kind of bonds develop by intramembranous ossification?

A

Flat bones

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39
Q

Give 5 bones that develop by intramembranous ossification?

A
  • Skull bones
  • Maxilla
  • Mandible
  • Pelvis
  • Clavicle
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40
Q

How does the clavicle develop?

A

NAME?

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41
Q

What does intramembranous ossification contribute to?

A

Thickening of bones at periosteal surface

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42
Q

What kind of growth occurs due to intramembranous ossification?

A

Appositional growth

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43
Q

What happens in intramembranous ossification of flat bones in the fetus?

A

Mineral deposits within the many trabeculae radiate outwards from a central point, the early primary ossification centre

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44
Q

Is intramembranous ossification complete in a newborn?

A

No

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45
Q

What is the advantage of the incompletion of intramembranous ossification in the newborn/

A

Makes scalp able to withstand trauma

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46
Q

What does the periosteum of newly forming flat bones contain?

A

Osteoprogenitor cells for bone deposition

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47
Q

What happens to osteoprogenitor cells?

A

They will merge to form woven immature bone

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48
Q

What does newly formed bone contain?

A

Bone marrow, blood vessels and mesenchymal tissue

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49
Q

What does compact bone of the skull during postnatal development have?

A

Osteocytes, osteons, Haversian and Volkmann’s canals

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50
Q

What is the result of the components of the compact bone of the skull during postnatal development being what they are?

A

Make it indistinguishable from bone arising from endochondral ossification

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51
Q

What is the inheritance pattern of osteogenesis imperfecta?

A

Autosomal dominant

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52
Q

What is osteogenesis imperfecta a disorder of?

A

Connective tissue

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53
Q

What causes osteogenesis imperfecta?

A

Mutations in the gene for type I collagen

54
Q

What does osteogenesis imperfecta affect?

A
  • Skeleton
  • Joints
  • Ears
  • Ligaments
  • Teeth
  • Sclerae
  • Skin
55
Q

Why is osteogenesis imperfecta of medicolegal importance?

A

Because of the possible confusion with multiple fractures caused by deliberate injury

56
Q

How can osteogenesis imperfecta be seen?

A

NAME?

57
Q

Where is growth hormone (GH) synthesised and stored?

A

Anterior pituitary

58
Q

What effect can abnormal GH levels have before puberty?

A
  • Excessive GH can cause gigantism

- Insufficient GH can affect epiphyseal cartilage and cause pituitary dwarfism

59
Q

Why can excessive GH cause gigantism?

A

Through promotion of epiphyseal growth plate activity

60
Q

What can abnormal GH levels cause in an adult?

A

Excessive GH may cause an increase in bone width

61
Q

Why can’t excessive GH cause gigantism in an adult?

A

There are no longer any epiphyseal growth plates

62
Q

How can GH cause an increase in bone width in an adult?

A

By promoting periosteal growth

63
Q

What is increased bone width known as?

A

Acromegaly

64
Q

What is increased GH production in adults normally caused by?

A

A benign tumour of the pituitary gland

65
Q

Why are sex hormones important in bone development?

A

They influence the development of ossification centres

66
Q

What are the sex hormones?

A
  • Androgens in men
  • Oestrogen’s in women

Both hormones present in each sex

67
Q

What is the role sex hormones?

A
  • Induce secondary sexual characteristics

- Give rise to pubertal growth spurt

68
Q

What can be bought about sex hormone producing tumours?

A

Precocious sexual maturity

69
Q

What effect can precocious sexual maturity have on bone growth?

A

Retards it

70
Q

Why can precocious sexual maturity retard bone growth?

A

Because of premature closure (fusion) of epiphyses

71
Q

What can happen if sex hormone is deficient?

A

Epiphyseal plates may persist later into life than they normally would, leading to prolonged bone growth and tall stature

72
Q

What kind of effects do neonatal hypothyroidism have?

A

Deleterious

73
Q

How can the deleterious effects of neonatal hypothyroidism be reversed?

A

Prompt administration of thyroxine

74
Q

What can happen if thyroid hormone deficiency is left untreated?

A

It can lead to infant with permanent neurological and intellectual damage, and a number of other abnormalities, including short stature

75
Q

What is osteoporosis?

A

A metabolic bone disorder in which mineralised bone is decreased in mass to the point that it no longer provides adequate mechanical support

76
Q

What does osteoporosis always reflect?

A

Enhanced bone resorption relative to formation

77
Q

What always characterises osteoporosis?

A

Depletion of bone mass

78
Q

What is loss of mass within the trabecular structure particular relevant to?

A

Increased susceptibility to bone fracture

79
Q

What is happening in osteoporotic bone?

A

Holes are being produced by osteoclasts, but not being replaced by osteoblasts

80
Q

What is osteoporosis associated with ageing a result of?

A

Incomplete filling of osteoclast resorption bays

81
Q

What may happen in the vertebrae of an osteoporosis sufferer?

A

NAME?

82
Q

What is the result of the effect of osteoporosis on the vertebrae?

A

Stooping, as the vertebrae become wedge shaped

83
Q

Who is osteoporosis a risk factor for?

A

The elderly

84
Q

When done bone mass peak?

A

25-35 years

85
Q

What is the problem with hip fractures?

A

They have complications in 12-20% of cases

86
Q

How does risk of hip fracture differ among sexes in whites?

A

2x higher in women

87
Q

How does risk of vertebral fracture differ among sexes in whites?

A

3x high in women

88
Q

What is the most common form of osteoporosis?

A

Primary- type 1 and 2

89
Q

Who does type 1 osteoporosis occur in?

A

Post menopausal women

90
Q

What is type 1 osteoporosis due to?

A

Increased osteoclast number

91
Q

Why do post menopausal women have a increase osteoclast number?

A

Due to oestrogen withdrawal

92
Q

Who does type 2 osteoporosis occur in?

A

Elderly people, generally after age of 70

93
Q

What causes type 2 osteoporosis?

A

Attenuated osteoblast function

94
Q

What are the risk factors for osteoporosis?

A
  • Genetic
  • Insufficient calcium intake
  • Insufficient calcium absorption
  • Exercise
  • Cigarette smoking
95
Q

What ethnic group is less prone to osteoporosis?

A

Blacks

96
Q

Why are blacks less prone to osteoporosis?

A

Because they have a higher peak bone mass than whites or asians

97
Q

Why does calcium absorption decrease with age?

A

Due to decreased renal activation of vitamin D

98
Q

When may vitamin D levels be a factor in osteoporosis?

A

NAME?

99
Q

What may cause the immobilisation of bone?

A

NAME?

100
Q

What does immobilisation of bone lead to?

A

Acceleration of bone loss

101
Q

What is needed to maintain bone mass?

A

Physical activity

102
Q

Who is cigarette smoking a risk factor for osteoporosis?

A

Women

103
Q

What is one of the most common forms of short limb dwarfism?

A

Achondroplasia

104
Q

In what respects are achondroplastic dwarfs normal?

A
  • They have normal mentation

- Average lifespan

105
Q

What causes achondroplasia?

A

An autosomal dominant point mutation in the fibroblast growth factor receptor-3 gene (FGFR3), causing a gain of function

106
Q

What is the result of the gain in function of the FGFR3 gene?

A
  • Decreased endochondrial ossification
  • Inhibited proliferation of chondrocytes in growth plate cartilage
  • Decreased cellular hypotrophy
  • Decreased cartilage matrix production
107
Q

What is the appearance of a sufferer of achondroplasia?

A
  • Very short limbs
  • Normal length trunk
  • Vault of the skull enlarged
  • Small face
  • Bridge of nose often flattened
108
Q

What % of achondroplasia cases are a result of a new mutation?

A

More then 80%

109
Q

What happens in 2 parents with achondroplasia have a child?

A
  • 25% chance child will die soon after birth
  • 50% chance child heterozygous, and has achondroplasia
  • 25% chance child will have normal phenotype
110
Q

Why is there a 25% chance that the child of two achondroplastic parents will die shortly after birth?

A

The homozygous condition is fatal

111
Q

How does the growth plate differ in a person with achondroplasia?

A

NAME?

112
Q

How does the body obtain vitamin D?

A

NAME?

113
Q

What happens to vitamin D in the body?

A

It undergoes hydroxylation in the liver, and then further hydroxylation in the kidney to form active 1,25-dihydroxyvitamin D

114
Q

What does 1,25-dihydroxyvitamin D do?

A

NAME?

115
Q

What does the opposite of vitamin D?

A

PTH

116
Q

Who does rickets occur in?

A

Children

117
Q

What happens in rickets?

A

Bones do not harden due to a deficiency in vitamin D

118
Q

Among whom is rickets most common in the UK?

A

Asian immigrant families

119
Q

Why is rickets more common in asian immigrant families?

A

The pigmentation of their skin means they can’t take vitamin D from the sun as well

120
Q

Why is there not adequate bone rigidity in rickets?

A

Insufficient calcium deposition

121
Q

What happens to the bones in rickets?

A

They become soft and malformed

122
Q

What happens in extreme cases of rickets?

A

Distortion of the skull bone, leading to bossing

123
Q

What is rickets rosary?

A

Enlargement of the costochondral junction of the ribs

124
Q

What is the adult counterpart of rickets?

A

Osteomalacia

125
Q

What causes osteomalacia?

A

Significant calcium deficiency or lack of vitamin D

126
Q

What can lead to calcium deficiency or vitamin D lack?

A
  • Poor diet
  • Lack of sunshine
  • Intestinal malabsorption
  • Liver/kidney disease
127
Q

What are the common symptoms of osteomalacia?

A
  • Back ache
  • Bone ache
  • Muscle weakness
128
Q

What has happened to the bones in osteomalacia?

A

The trabeculae of cancellous bone have abnormally large amount of non-mineralised bone (osteoid) covering their trabecular surface

129
Q

What is the result of insufficient mineralisation of trabeculae?

A

They are weakened

130
Q

What are the most common fracture sites?

A
  • Femoral neck
  • Pubic ramus
  • Spine
  • Ribs

Z OLD Tissues of the Body (19 decks)

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