Bone

Question 1

How do flat bones develop?

Answer 1

By intramembranous ossification

Question 2

Give four examples of flat bones

Answer 2

Skull
Clavicle
Scapula
Pelvic bones

Question 3

What is the difference between endochondral and intramembranous ossification?

Answer 3

Endochondral forms most of the bones in the body (long bones) and replaces cartilage with bone
Intramembranous forms flat bones and the bone is formed in layers of membrane-resembling sheets

Question 4

What are the stages of intramembranous ossification? (5)

Answer 4

1. MSCs form nidus
2. MSCs become osteoprogenitor cells
3. Osteoprogenitor cells become osteoblasts and lay down extracellular matrix containing type I collagen (osteoid)
4. Osteoid mineralises to form rudimentary bone tissue spicules, surrounded by osteoblasts and osteocytes
5. Spicules join to form trabeculae which merge to form woven bone, which is replaced by lamellae of mature compact bone

Question 5

What is a nidus?

Answer 5

Tight cluster of cells

Question 6

What are the spaces in cancellous bone filled by?

Answer 6

Bone marrow

Question 7

What do the Haversian and Volkmann’s canals carry?

Answer 7

Blood vessels
Lymph vessels
Nerves

Question 8

What is the difference between immature and mature bone?

Answer 8

Mature bone has osteocytes arranged in concentric lamellae of osteons whereas immature bone has randomly arranged osteocytes

Question 9

What is another name given to cancellous bone?

Answer 9

Spongy bone

Question 10

What makes up 65% of bone?

Answer 10

Mineral (calcium hydroxyapatite crystals)

Question 11

How does bone resist fracture?

Answer 11

Has great tensile and compressive strength but also has degree of flexibility

Question 12

What results in a haematoma?

Answer 12

When a bone breaks, bleeding from multiple broken vessels can result in a haematoma between broken bone ends

Question 13

In simple terms, what are the four stages of fracture repair?

Answer 13

1. Haematoma formed in which granulation tissue arises
2. Procallus of granulation tissue is replaced by fibrocartilaginous callus in which bony trabeculae are developing
3. Endochondral and intramembranous ossification give rise to bony callus of cancellous bone
4. Cancellous bone replaced by compact cortical bone until remodelling is complete

Question 14

By which process do blood vessels develop in fracture repair?

Answer 14

Angiogenesis

Question 15

What is osteoporosis?

Answer 15

Metabolic bone disease in which mineralised bone is decreased in mass to the point that it no longer provides adequate mechanical support

Question 16

Complete the sentence:

Osteoporosis associated with ageing results from incomplete filling of __________ _________ ____.

Answer 16

Osteoclast resorption bays

Question 17

Describe type 1 osteoporosis

Answer 17

Occurs in postmenopausal women and is due to increase in osteoclast number as a result of oestrogen withdrawal

Question 18

Describe type 2 osteoporosis

Answer 18

Occurs in elderly people of both genders and occurs after 70 years old and reflects attenuated osteoblast function

Question 19

What are the risk factors of osteoporosis? (5)

Answer 19

1. Genetic (peak bone mass higher in blacks than in whites or Asians)
2. Insufficient calcium intake
3. Insufficient calcium absorption and vit D
4. Lack of exercise
5. Cigarette smoking