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(BMED) TOB 1-5 > 5.2 - Ossification and Bone Disease > Flashcards

5.2 - Ossification and Bone Disease Flashcards

1
Q 
Match the component of bone to its corresponding percentage. 
1.	Type I collagen 
2.	Non-collagen proteins 
3.	Calcium hydroxyapatite
4.	Water
65%, 23%, 10%, 2%
A

Calcium hydroxyapatite: 65%
Type I collagen: 23%
Water: 10%
Non-collagen proteins: 2%

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2
Q

What is diploe?

A

The spongy bone layer separating the inner and outer layers of the cortical bone of the skull

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3
Q

What type of bone would you find at the internal and external surfaces of flat bone?

A

Cortical

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4
Q

What type of bone would you find in the central regions of flat bone?

A

Spongy

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5
Q

Brittle bone disease is also known as ___.

A

Osteogeneses imperfecta

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6
Q

How many types of osteogenesis imperfecta are there?

A

8

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7
Q

What is the genetic basis for type I-IV osteogenesis imperfecta?

A

Mutation on COL1A1 or COL1A2, which code for type I collagen

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8
Q

What is the inheritance pattern for type I-IV osteogenesis imperfecta?

A

Autosomal dominant

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9
Q

What is the incidence of osteogenesis imperfecta?

A

1/10,000 births in the US

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10
Q

Osteogenesis imperfecta has systemic implications (i.e., affects skeleton, joints, ears, ligaments, teeth, sclera, and skin). Why is this so?

A

Results from defective synthesis of collagen, which is present all over the body

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11
Q

What is the genetic basis for type I osteogenesis imperfecta?

A

Loss of COL1A1 gene -> insufficient collagen

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12
Q

What is the genetic basis for type II osteogenesis imperfecta?

A

Altered function of COL1A1 gene or COL1A2 gene -> abnormal collagen

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13
Q

Compare the genetic basis for type I and II osteogenesis imperfecta.

A

Type I: loss of COL1A1 gene -> insufficient collagen

Type II: altered function of COL1A1 gene or COL1A2 gene -> abnormal collagen

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14
Q

What is the mildest form of osteogenesis imperfecta?

A

Type I

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15
Q

What is the most common form of osteogenesis imperfecta?

A

Type I

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16
Q

What is the most severe form of osteogenesis imperfecta?

A

Type II

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17
Q

List 6 symptoms of type I osteogenesis imperfecta.

A
  1. Blue sclera
  2. Fusion of auditory ossicles
  3. Frequent fractures
  4. Unstable joints
  5. Thin bones
  6. Abnormally curved bones
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18
Q

Why might someone with osteogenesis imperfecta experience hearing loss?

A

Fusion of auditory ossicles

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19
Q

What are the auditory ossicles?

A

Three tiny bones in the middle ear responsible for transmitting sound

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20
Q

Why might someone with osteogenesis imperfecta be of shorter stature?

A

Defective synthesis of type I collagen hinders bone growth

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21
Q

Why is type II osteogenesis imperfecta lethal?

A

Almost all the bones fracture during labour or delivery

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22
Q

Why might osteogenesis imperfecta have medicolegal importance?

A

Can be mistaken for fractures caused by child abuse

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23
Q

What is another name for somatotropin?

A

Growth hormone (GH)

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24
Q

Where is growth hormone synthesized?

A

Anterior pituitary

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25
Q

Which hormone promotes growth of epiphyseal cartilage?

A

Growth hormone (GH)

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26
Q

What is the impact of excessive growth hormone (GH) before puberty?

A

Gigantism through promotion of epiphyseal growth plate activity

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27
Q

What is the impact of insufficient growth hormone (GH) before puberty?

A

Pituitary dwarfism due to lack of epiphyseal growth plate activity

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28
Q

How does excessive GH before puberty cause gigantism?

A

Promotion of epiphyseal growth plate activity

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29
Q

How does insufficient GH before puberty cause pituitary dwarfism?

A

Lack of epiphyseal growth plate activity

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30
Q

What is the most common form of proportionate dwarfism?

A

Pituitary dwarfism

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31
Q

What is the impact of excessive growth hormone (GH) after puberty?

A

Acromegaly (i.e., increase in bone width)

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32
Q

In adults, excessive GH causes acromegaly. It cannot cause gigantism. Why?

A

Epiphyseal growth plates have closed

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33
Q

List 3 symptoms of acromegaly.

A
  1. Enlarged hands
  2. Enlarged feet
  3. Enlarged facial features
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34
Q

What is acromegaly?

A

Increase in bone width due to excessive growth hormone after puberty

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35
Q

What gives rise to the pubertal growth spurt?

A

Increase in androgens and estrogens stimulates osteoblast activity and inhibits osteoclast activity

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36
Q

Sex-hormone producing tumours can trigger early sexual maturity. How might this inhibit bone growth?

A

Premature closure of epiphyseal growth plates

37
Q

Deficiency in sex hormones can delay sexual maturity. How might this lead to prolonged bone growth and tall stature?

A

Delayed closure of epiphyseal growth plates

38
Q

What is cretinism?

A

Stunted physical and mental growth due to congenital hypothyroidism

39
Q

What is the most common cause of cretinism?

A

Iodine deficiency in the mother’s diet during pregnancy

40
Q

How would you treat neonatal hypothyroidism?

A

Administration of thyroxine

41
Q

List 3 processes mediated by thyroxine.

A
  1. Metabolic rate
  2. Neural maturation
  3. Bone growth
42
Q

Why are thyroid hormones important for bone development?

A

Stimulate bone growth

43
Q

Compare the importance of thyroid hormones in the bone development of infants and adults.

A

Infants: big effect
Adults: inconsequential; bone development largely mediated by PTH

44
Q

Approximately how many people in the UK suffer from osteoporosis?

A

3 million

45
Q

Describe, in broad terms, how osteoporosis reduces bone mineral density.

A

Osteoclast activity outweighs osteoblast activity

46
Q

Osteoporosis is associated with reduced mechanical strength and increased susceptibility to fracture. What type of bone is most commonly affect by osteoporosis?

A

Spongy

47
Q

What are the 3 most common sites of fractures in osteoporosis?

A
  1. Wrists
  2. Hips
  3. Spine
48
Q

Why are elderly people more susceptible to osteoporotic fractures?

A

Bone mass declines with age

49
Q

At what age does bone density peak?

A

25-30

50
Q

At what age does bone density begin to decline?

A

~40

51
Q

What is the first line pharmacological treatment for osteoporosis?

A

Bisphosphonates

52
Q

How do bisphosphonates treat osteoporosis?

A

Inhibit osteoclast activity

53
Q

Which type of osteoporosis is associated with post-menopausal women?

A

Type 1

54
Q

Which type of osteoporosis is associated with aging past 70?

A

Type 2

55
Q

Which type of osteoporosis results in increased osteoclast activity?

A

Type 1

56
Q

Which type of osteoporosis results in decreased osteoblast activity?

A

Type 2

57
Q

Compare type 1 and type 2 osteoporosis.

A

Type 1: a.k.a. postmenopausal osteoporosis, onset in age 45 to 55, results in increased osteoclast activity
Type 2: a.k.a. senile osteoporosis, onset in age 70+, results in decreased osteoblast activity

58
Q

List 8 risk factors for osteoporosis.

A
  1. Old age
  2. Female
  3. Estrogen deficiency (e.g., menopause)
  4. Hypogonadism
  5. Long term steroid treatment
  6. Diet (poor calcium or Vitamin D)
  7. Immobility
  8. Family history
59
Q

Which ethnicity reaches higher peak bone density?

A

Black

60
Q

What is the recommended calcium intake for postmenopausal women?

A

800 mg/day

61
Q

Why might elderly confined INDOORS be at greater risk of osteoporosis?

A

Vitamin D deficiency hinders bone mineralization

62
Q

Why might prolonged bed rest increase risk for osteoporosis?

A

Physical activity is needed to remodel bone

63
Q

Which might application of a cast increase risk for osteoporosis?

A

Immobility hinders bone remodelling

64
Q

Why might kidney disease increase risk for osteoporosis?

A

Decreased renal activation of vitamin D3 hinders bone mineralisation

65
Q

What is the most common cause of short-limbed dwarfism?

A

Achondroplasia

66
Q

What is the inheritance pattern for achondroplasia?

A

Autosomal dominant (nb: homozygous condition is LETHAL)

67
Q

Explain the genetic basis for achondroplasia.

A

Point mutation in the FGFR3 gene (encodes for fibroblast growth factor receptor 3) promotes early growth plate closure

68
Q

The inheritance pattern for achondroplasia is autosomal dominant. However, more than 80% of people with achondroplasia are born to parents without the condition. What accounts for this?

A

Spontaneous mutation

69
Q

Two parents with achondroplasia have a child. Which phenotype would be lethal, and what are the odds that the child is born with the phenotype?

A

Homozygous dominant

25%

70
Q

Two parents with achondroplasia have a child. Which phenotype would result in a child who presents with achondroplasia, and what are the odds that the child is born with the phenotype?

A

Heterozygous

50%

71
Q

Two parents with achondroplasia have a child. Which phenotype would result in a living child without achondroplasia, and what are the odds that the child is born with the phenotype?

A

Homozygous recessive

25%

72
Q

What is a synonym of calcitriol?

A

Vitamin D3

73
Q

What is the cholesterol precursor for vitamin D3?

A

7-dehydrocholesterol

74
Q

Which vitamin results from the hydroxylation of 7-dehydrocholesterol in the liver and kidney?

A

Vitamin D3

75
Q

How is 7-dehydrocholesterol converted to vitamin D3?

A

Hydroxylated in the liver and kidney

76
Q

What are the 2 ways that vitamin D increases bone mineralization?

A
  1. Increases availability of Ca+ by increasing its absorption in the intestine
  2. Directly stimulates bone remodeling
77
Q

What is osteomalacia?

A

Softening of the bone; caused by INSUFFICIENT MINERALIZATION

78
Q

What Is rickets?

A

Childhood version of osteomalacia

79
Q

List 3 deficiencies that can cause insufficient mineralization of bone (i.e., osteomalacia or rickets).

A
  1. Vitamin D
  2. Calcium
  3. Phosphate
80
Q

In the UK, which ethnic demographic most commonly suffers from rickets?

A

Asian immigrant families

81
Q

In rickets, insufficient mineral deposition leads to bones becoming soft and malformed. List 3 characteristic malformations.

A
  1. Bowed legs
  2. Skull bossing
  3. Rickety rosary
82
Q

List 3 risk factors for vitamin D deficiency.

A
  1. Poor dietary intake
  2. Lack of sunshine
  3. Liver or kidney disease
83
Q

What are 4 common symptoms of osteomalacia?

A
  1. Bone pain
  2. Back pain
  3. Muscle weakness
  4. Increased risk of fracture
84
Q

What are the 4 most common sites of fracture for osteomalacia?

A
  1. Femoral neck
  2. Pubic ramus
  3. Spine
  4. Ribs
85
Q

What cellular changes occur in osteomalacia?

A

Trabeculae weakened by thick layers of non-mineralized osteoid

86
Q

Which hormone inhibits osteoclast activity?

A

Calcitonin

87
Q

Which hormone opposes the actions of PTH?

A

Calcitonin

88
Q

Compare rickets and osteomalacia.

A

Rickets: affects children, affects growing bone
Osteomalacia: affects adults, affects bone remodeling

89
Q

Why is the skull unaffected in achondroplasia?

A

Disease leads to premature closing of growth plates, affecting endochondral ossification; skull undergoes intramembranous ossification

(BMED) TOB 1-5 (8 decks)

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