Ossification and bone disease

Question 1

Epiphyseal plates are where which type of cartilage is found?

Answer 1

Hyaline cartilage

Question 2

What are the name of the 5 zones of the epiphyseal growth plate? (In direction of which growth occurs)

Answer 2

1. Zone of resorption 2. Zone of calcified cartilage 3. Zone of hypertrophy 4. Zone of proliferation 5. Zone of reserve cartilage

Question 3

In the zone of resorption, small blood vessels and connective tissue invades the regions left behind by dying chondrocytes. This leaves behind calcified cartilage called …..

Answer 3

Spicules

Question 4

In which zone of the epiphyseal growth plate do cells divide to form columns?

Answer 4

Zone of proliferation

Question 5

What is intramembranous ossification?

Answer 5

It takes place within condensations of mesenchymal tissue and not by replacement of a pre-existing hyaline cartilage template

Question 6

Which type of bones tend to develop by intramembranous ossification?

Answer 6

Flat bones

Question 7

Mutations in type 1 collagens form a condition called ….. ….. Sufferers tend to have many fractures, blue sclerae, thin or curved bones etc. There are four types.

Answer 7

Osteogenesis imperfecta

Question 8

If you have excessive GH as an adult, what condition results?

Answer 8

Acromegaly. GH causes increased periosteal growth and bone width

Question 9

Why does early sexual maturity retard bone growth?

Answer 9

Early sexual maturity causes the permature closure of epiphyses

Question 10

Neonatal hypothyroidism if not spotted leads to …….

Answer 10

Cretinism

Question 11

What am I describing? A metabolic disease in which mineralised bone is decreased in mass to the point that is no longer provides adequate support.

Answer 11

Osteoporosis

Question 12

Give an example of a risk factor of osteoporosis.

Answer 12

• Age
• Women who are post menopausal
• Insufficient calcium intake and absorption
• lack of vitamin D
• Genetic factors
• Lack of exercise
• Cigarette smoking

Question 13

Which type of primary osteoporosis is associated with postmenopausal women?

Answer 13

Type 1

Question 14

Why are postmenopausal women at increased risk of osteoporosis?

Answer 14

There is a decrease in osteoclast number as a result of oestrogen withdrawal.

Question 15

Type 2 primary osteoporosis is associated with the elderly. Why does risk of osteoporosis increase with age?

Answer 15

As age increases osteoblast function is attenuated

Question 16

What is the effect of the mutation in the FGFR3 gene in achondroplasia?

Answer 16

• Decreased endochondral ossification
• Inhibited proliferation of chondrocytes in the growth plate cartilage
• Decreased cellular hypertrophy
• Decreased cartilage matrix production

Question 17

What is the effect of vitamin D on bone?

Answer 17

It promotes mineralization of bone

Question 18

What is rickets?

Answer 18

A childhood deficiency of vitamin D resulting in insufficient calcium deposition.

Question 19

What are the symptoms of rickets?

Answer 19

Bossing of the skull, enlargement of costchondral junctions, bones become soft and deformed

Question 20

What is osteomalacia?

Answer 20

It is vitamin D deficiency as an adult. Trabeculae of cancellous bone has abnormally large amount of non-mineralised bone covering their surface.

Question 21

What are the symptoms of osteomalacia?

Answer 21

Back pain, back ache and muscle weakness.

Question 22

What is endochondral ossification?

Answer 22

It involves the replacement of a pre-existing hyaline cartilage template by bone and is the way by which most of the bones of the body develop.