Ossification and Bone Disease Flashcards Preview

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

Flashcards in Ossification and Bone Disease Deck (130):
1

What does endochondral ossification involve?

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

2

What is endochondral ossification the mechanism for?

The development of most of the bones in the body

3

Where is endochondral ossification particularly important?

Mostly in long bones

4

Where does endochondral ossification occur?

Foetus

5

What does endochondral ossification in the foetus form?

The skeleton

6

What part of long bones become ossified first?

Diaphyses

7

What is the precursor for most bones?

A hyaline cartilage model

8

What happens in endochondral ossification?

Cartilage is mineralised to form bone

9

What do growing bones have?

Growth plates of hyaline cartilage

10

How long does the femur continue to grow for?

Into adulthood

11

How does the femur continue to grow into adulthood?

By continuous production of cartilage

12

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

Shaft side

13

What happens after the cessation of long bone growth?

The epiphyseal plate disappears

14

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

None- it’s purely the hyaline cartilage model

15

When does endochondral ossification occur?

In a 5-6 week embryo

16

What happens in a 5-6 week old embryo?

A collar of periosteal bone appears in the shaft

17

What happens in an 8-12 week old fetus?

- The central cartilage calcifies
- Nutrient artery penetrates 
- Formation of the primary ossification centre

18

What does the nutrient artery provide?

Bone-depositing osteogenic cells

19

What happens regarding bone development postnatal?

- Medulla becomes calcified bone 
- Cartilage forms epiphyseal growth plates 
- Epiphyses develop secondary centres of ossification

20

What happens regarding bone development prepubertally?

Epiphyses ossify and growth plates continue to move apart

21

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

Bone lengthening

22

What happens regarding bone development in a mature adult?

#NAME?

23

How does bone increase in length?

Endochondral ossification

24

How does bone increase in girth?

Periosteal ossification

25

What is periosteal ossification?

Intramembranous ossification

26

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

Columns of calcified cartilage

27

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

It becomes mineralised

28

What are the 5 zones of the epiphyseal growth plates?

- Zone of reserve cartilage 
- Zone of proliferation 
- Zone of hypertrophy 
- Zone of calcified cartilage
- Zone of resorption

29

What is not happening in the zone of reserve cartilage?

- Cellular proliferation 
- Active matrix production

30

What happens in the zone of proliferation?

#NAME?

31

What happens in the zone of hypertrophy?

#NAME?

32

What happens in the zone of calcified cartilage?

#NAME?

33

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

The marrow cavity

34

What happens in the zone of resorption?

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

35

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

Bone is laid down

36

Where does intramembranous ossification take place?

Within condensations of mesenchymal tissue

37

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

No

38

What kind of bonds develop by intramembranous ossification?

Flat bones

39

Give 5 bones that develop by intramembranous ossification?

- Skull bones
- Maxilla 
- Mandible 
- Pelvis 
- Clavicle

40

How does the clavicle develop?

#NAME?

41

What does intramembranous ossification contribute to?

Thickening of bones at periosteal surface

42

What kind of growth occurs due to intramembranous ossification?

Appositional growth

43

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

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

44

Is intramembranous ossification complete in a newborn?

No

45

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

Makes scalp able to withstand trauma

46

What does the periosteum of newly forming flat bones contain?

Osteoprogenitor cells for bone deposition

47

What happens to osteoprogenitor cells?

They will merge to form woven immature bone

48

What does newly formed bone contain?

Bone marrow, blood vessels and mesenchymal tissue

49

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

Osteocytes, osteons, Haversian and Volkmann’s canals

50

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

Make it indistinguishable from bone arising from endochondral ossification

51

What is the inheritance pattern of osteogenesis imperfecta?

Autosomal dominant

52

What is osteogenesis imperfecta a disorder of?

Connective tissue

53

What causes osteogenesis imperfecta?

Mutations in the gene for type I collagen

54

What does osteogenesis imperfecta affect?

- Skeleton 
- Joints
- Ears
- Ligaments
- Teeth
- Sclerae
- Skin

55

Why is osteogenesis imperfecta of medicolegal importance?

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

56

How can osteogenesis imperfecta be seen?

#NAME?

57

Where is growth hormone (GH) synthesised and stored?

Anterior pituitary

58

What effect can abnormal GH levels have before puberty?

- Excessive GH can cause gigantism 
- Insufficient GH can affect epiphyseal cartilage and cause pituitary dwarfism

59

Why can excessive GH cause gigantism?

Through promotion of epiphyseal growth plate activity

60

What can abnormal GH levels cause in an adult?

Excessive GH may cause an increase in bone width

61

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

There are no longer any epiphyseal growth plates

62

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

By promoting periosteal growth

63

What is increased bone width known as?

Acromegaly

64

What is increased GH production in adults normally caused by?

A benign tumour of the pituitary gland

65

Why are sex hormones important in bone development?

They influence the development of ossification centres

66

What are the sex hormones?

- Androgens in men
- Oestrogen's in women 

Both hormones present in each sex

67

What is the role sex hormones?

- Induce secondary sexual characteristics 
- Give rise to pubertal growth spurt

68

What can be bought about sex hormone producing tumours?

Precocious sexual maturity

69

What effect can precocious sexual maturity have on bone growth?

Retards it

70

Why can precocious sexual maturity retard bone growth?

Because of premature closure (fusion) of epiphyses

71

What can happen if sex hormone is deficient?

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

72

What kind of effects do neonatal hypothyroidism have?

Deleterious

73

How can the deleterious effects of neonatal hypothyroidism be reversed?

Prompt administration of thyroxine

74

What can happen if thyroid hormone deficiency is left untreated?

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

75

What is osteoporosis?

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

76

What does osteoporosis always reflect?

Enhanced bone resorption relative to formation

77

What always characterises osteoporosis?

Depletion of bone mass

78

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

Increased susceptibility to bone fracture

79

What is happening in osteoporotic bone?

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

80

What is osteoporosis associated with ageing a result of?

Incomplete filling of osteoclast resorption bays

81

What may happen in the vertebrae of an osteoporosis sufferer?

#NAME?

82

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

Stooping, as the vertebrae become wedge shaped

83

Who is osteoporosis a risk factor for?

The elderly

84

When done bone mass peak?

25-35 years

85

What is the problem with hip fractures?

They have complications in 12-20% of cases

86

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

2x higher in women

87

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

3x high in women

88

What is the most common form of osteoporosis?

Primary- type 1 and 2

89

Who does type 1 osteoporosis occur in?

Post menopausal women

90

What is type 1 osteoporosis due to?

Increased osteoclast number

91

Why do post menopausal women have a increase osteoclast number?

Due to oestrogen withdrawal

92

Who does type 2 osteoporosis occur in?

Elderly people, generally after age of 70

93

What causes type 2 osteoporosis?

Attenuated osteoblast function

94

What are the risk factors for osteoporosis?

- Genetic
- Insufficient calcium intake 
- Insufficient calcium absorption 
- Exercise 
- Cigarette smoking

95

What ethnic group is less prone to osteoporosis?

Blacks

96

Why are blacks less prone to osteoporosis?

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

97

Why does calcium absorption decrease with age?

Due to decreased renal activation of vitamin D

98

When may vitamin D levels be a factor in osteoporosis?

#NAME?

99

What may cause the immobilisation of bone?

#NAME?

100

What does immobilisation of bone lead to?

Acceleration of bone loss

101

What is needed to maintain bone mass?

Physical activity

102

Who is cigarette smoking a risk factor for osteoporosis?

Women

103

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

Achondroplasia

104

In what respects are achondroplastic dwarfs normal?

- They have normal mentation 
- Average lifespan

105

What causes achondroplasia?

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

106

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

- Decreased endochondrial ossification
- Inhibited proliferation of chondrocytes in growth plate cartilage 
- Decreased cellular hypotrophy 
- Decreased cartilage matrix production

107

What is the appearance of a sufferer of achondroplasia?

- Very short limbs 
- Normal length trunk
- Vault of the skull enlarged
- Small face
- Bridge of nose often flattened

108

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

More then 80%

109

What happens in 2 parents with achondroplasia have a child?

- 25% chance child will die soon after birth
- 50% chance child heterozygous, and has achondroplasia
- 25% chance child will have normal phenotype

110

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

The homozygous condition is fatal

111

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

#NAME?

112

How does the body obtain vitamin D?

#NAME?

113

What happens to vitamin D in the body?

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

114

What does 1,25-dihydroxyvitamin D do?

#NAME?

115

What does the opposite of vitamin D?

PTH

116

Who does rickets occur in?

Children

117

What happens in rickets?

Bones do not harden due to a deficiency in vitamin D

118

Among whom is rickets most common in the UK?

Asian immigrant families

119

Why is rickets more common in asian immigrant families?

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

120

Why is there not adequate bone rigidity in rickets?

Insufficient calcium deposition

121

What happens to the bones in rickets?

They become soft and malformed

122

What happens in extreme cases of rickets?

Distortion of the skull bone, leading to bossing

123

What is rickets rosary?

Enlargement of the costochondral junction of the ribs

124

What is the adult counterpart of rickets?

Osteomalacia

125

What causes osteomalacia?

Significant calcium deficiency or lack of vitamin D

126

What can lead to calcium deficiency or vitamin D lack?

- Poor diet
- Lack of sunshine 
- Intestinal malabsorption 
- Liver/kidney disease

127

What are the common symptoms of osteomalacia?

- Back ache 
- Bone ache
- Muscle weakness

128

What has happened to the bones in osteomalacia?

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

129

What is the result of insufficient mineralisation of trabeculae?

They are weakened

130

What are the most common fracture sites?

- Femoral neck
- Pubic ramus 
- Spine
- Ribs