Bone Function and Repair

Question 1

Name the three categories of bone function

Answer 1

• Mechanical
• Synthetic (Haemopoiesis)
• Metabolic (Fat/Mineral Storage)

Question 2

What are the two types of Ossification?

Answer 2

Endochondral - Formation of long bone from cartilage template

Intracellular-Membranous - Formation of bone by clusters of Mesenchymal Stem Cells in centre of the bone

Question 3

Describe the 3 stages of Intracellular-Membranous Ossification

Answer 3

1. Mesenchymal stem cells aggregate and differentiate into Osteoblasts
2. Ossification occurs and bone spicules spread and interconnect
3. Blood vessels get trapped and form Cancellous bone

Question 4

What does Intracellular-Membranous Ossification produce?

Answer 4

Immature bone that can be remodelled into mature bone

Question 5

Describe the 3 stages of Intra-Membranous Ossification of Flat Bone

Answer 5

1. Mesenchymal Stem Cells > Osteoprogenitor Cells > Osteoblasts
2. Osteoblasts lay down an Osteoid which mineralises into bone tissue Spicules
3. Spicules join to form Trabeculae and Lamellae of mature Corticol bone

Question 6

What is Appositional Growth?

Answer 6

Growth accomplished by the addition of new layers to those previously formed

Question 7

Describe Appositional Growth in Cartilage in terms of Chondrocytes

Answer 7

1. Chondrocytes separate and enlarge
2. Calcified Cartilage is replaced by bone
3. Bone is added to Diaphysis

Question 8

What increases and what stays the same in Appositional Growth?

Answer 8

• Length of bone increases

- Epiphyseal plate remains unchanged

Question 9

What stages occur in Appositional bone growth?

Answer 9

• Extracellular matrix is ossified
• Osteoblasts add bone by Appositional Growth
• Osteoclasts degrade bone round edges

Question 10

What are the fundamental functional units of compact bone called?

Answer 10

Osteons

Question 11

What 4 structures compose an Osteon and what is their purpose?

Answer 11

Osteocytes - Bone forming cells joined by long projections
Haversian/Volkmann’s Canals - Carry arteries, veins, lymph vessels and nerves
Reabsorption Canal - Starting point for remodelling

Question 12

What is the difference in Osteocyte arrangement between immature and mature bone?

Answer 12

Immature - Random arrangement

Mature - Arranged in concentric lamellae of osteons

Question 13

Does Cancellous bone contain blood vessels?

Answer 13

No as it is surrounded by red bone marrow and has spaces which contain bone marrow

Question 14

What 2 structural features contribute to bone strength?

Answer 14

• Lamellae that can slip past each other to resist force

- Osteons remodel themselves to thicken bone

Question 15

What are the 4 bone stability factors?

Answer 15

• Osteocyte Activity
• Osteoblast Activity
• Osteoclast Activity
• Nutrition

Question 16

Name 3 hormones that influence bone stability

Answer 16

• Oestrogen
• Testosterone
• Parathyroid Hormone
• Calcitonin

Question 17

Name 3 vitamins that contribute to bone strength

Answer 17

Vitamin A
Vitamin D3 - aids calcium absorption
Vitamin C - aids collagen synthesis
Vitamin K/B12 - role in bone protein synthesis

Question 18

State the 7 steps of bone repair

Answer 18

1. Haematoma formation
2. Tissue Death
3. Inflammation and Cellular Proliferation - Neutrophils/Osteoclasts
4. Formation of Granular Tissue - New blood vessels develop
5. Fibrocartilagenous Callus Formation - Collagen and Hyaline cartilage
6. Consolidation Callus Formation - Ossification to Cancellous bone
7. Bone Remodelling - Cancellous Bone > Compact Bone

Question 19

What are the two processes in Bone Remodelling called?

Answer 19

• Cutting Cone

- Closing Cone

Question 20

What happens in the stages of cutting and closing cone?

Answer 20

Cutting Cone - Osteoclasts make a wide tunnel in the bone

Closing Cone - Osteoblasts make a smaller tunnel of Corticol bone forming a new Osteon

Question 21

What increases fracture susceptibility?

Answer 21

Loss of trabecular bone mass

Question 22

Name 4 clinical conditions associated with bone fragility

Answer 22

• Osteogenesis Imperfecta
• Rickets
• Osteomalacia
• Osteoporosis
• Achondroplasia

Question 23

What deficiency causes Rickets and what effect does it have?

Answer 23

• Vitamin D deficiency

- Results in poor calcium mobilisation and ineffective mineralisation

Question 24

What is the effect of Rickets?

Answer 24

Soft bones which causes bowed legs

Question 25

Name 3 contributing factors of Osteomalacia

Answer 25

- Kidney Disease - Stomach/Intestine surgery - Drugs

Question 26

Name 2 differences between Type 1 and Type 2 primary Osteoporosis

Answer 26

Type 1 - Post-menopausal - Increase in osteoclasts - Due to loss of Oestrogen Type 2 - Senile - Loss of Osteoblast function and incomplete filling of Osteoclast resorption bays - Due to Loss of Oestrogen and Androgen

Question 27

What is the effect of Osteoporosis on the spine?

Answer 27

Causes vertebral collapse and shortening of the spinal column

Question 28

Name 3 modifiable risk factors of Osteoporosis

Answer 28

- Insufficient calcium intake - Exercise - Smoking

Question 29

Name 2 causes of Secondary Osteoporosis and what does it affect?

Answer 29

- Drug therapy - Metabolic Bone Disease - Affects Bone Remodelling

Question 30

Which Bone process does Achondroplasia affect?

Answer 30

Endochondrial Ossification meaning long bones cannot lengthen