Session 7: Bone

Question 1

Define endochondral ossification.

Answer 1

Replacement of a pre-existing hyaline Cartilage template by bone.

Question 2

Describe the difference sections of a long bone.

Answer 2

1. Diaphysis (shaft)
2. Metaphysis (wide portion which contains epiphyseal growth plates)
3. Epiphysis (end part)

Question 3

Describe the process of long bone development.

Answer 3

Endochondral Ossification

1. Initial hyaline Cartilage model
2. Collar of compact bone appears at shaft
3. Primary ossification centre forms (calcification by osteogenic cells)
4. Medulla becomes cancellous bone/ secondary ossification centres/ epiphyseal growth plates form
5. Epiphysis calcifies
6. Epiphyseal growth plates replaced by bone

Question 4

What is intramembranous ossification?

Answer 4

Increase in girth of bone

Question 5

Define intramembranous ossification.

Answer 5

Thickening of flat bones at periosteal surfaces (appositional growth)

Question 6

Name 3 flat bones.

Answer 6

1. Skull
2. Clavicle (collar bone)
3. Pelvic bones

Question 7

Describe the stages of intramembranous ossification.

Answer 7

1. Mesenchymal stem cells form clusters (nidus)
2. MSC become osteoprogenitor cells
3. Osteoprogenitor cells become osteoblasts
4. Lay down ECM (containing Type I collagen)- ostoid
5. Mineralises to form spicules
6. Spicules join and form trabeculae (woven bone)

Question 8

TRUE OR FLASE: Osteoclasts have multiple nuclei.

Answer 8

True

Question 9

What structures carry vessels within compact bone?

Answer 9

Haversian and volkmann’s canals

Question 10

Does this description match mature or immature bone?

• osteocytes arranged in concentric lamellae of osteons
• re-adsorprion cancels running parallel

Answer 10

Mature

Question 11

How do osteocytes share nutrients?

Answer 11

Long cytoplasmic processes connecting via gap junctions

Question 12

Why does spongy bone have no Haversian or volkmanns canals?

Answer 12

No requirement for external nutrient supply

Question 13

What cell type is essential in bone remodelling?

Answer 13

Osteoclasts

Question 14

Describe the stages of fracture repair.

Answer 14

1. Haematoma forms (clot)
2. Fibrocartilaginous callus formation (tissue rich in cappliaries and fibroblasts)
3. Bony callus formation (trabeculae develop)
4. Fracture repair

Question 15

Define autograft

Answer 15

Donor is recipient

Question 16

Define homograft

Answer 16

Donor is a different human

Question 17

Define heterograft

Answer 17

Donor is another species

Question 18

What is osteoporosis?

Answer 18

Bone disease when mineralised bone decreases in mass (loss of trabeculae) so it no longer provides enough support.

Question 19

Name 5 risk factors for Osteoporosis.

Answer 19

1. Genetics (bone mass higher in black peeps)
2. Calcium deficiency
3. Insufficient Vit D adsorbition
4. Lack of exercise
5. Smoking