Lecture 7

Question 1

What does bone start of as?

Answer 1

Cartilage.

Question 2

What is the process of cartilage turning to bone called?

Answer 2

Ossification

Question 3

Where does ossification first occur?

Answer 3

The diaphysis of the bone (shaft)

Question 4

Where is the secondary centre of ossification?

Answer 4

The epiphysis (the ends of long bones)

Question 5

Why is the epiphysis seperate to the diaphysis in children?

Answer 5

To allow for the diaphysis to grow and develop independently to the ends of the bones, where the joints are.

Question 6

Describe what a growth plate is and how it allows for bones to grow.

Answer 6

A growth plate is a cartilage disc located between the diaphysis and the epiphysis. This cartilage is continuously replaced my chondroblasts, and the old parts of cartilage form new bone, with the assistance of osteoblasts, hence the bone grows over time.

Question 7

What occurs to the diaphysis and growth plate after an individual has stopped growing?

Answer 7

Fusion of the epiphysis and diaphysis (fusion of the primary and secondary centres).

Question 8

How does a bone grow in width?

Answer 8

Osteoblasts located in the periosteum (outer layer of bone) build bone to increase the width.

Question 9

What is the medullary cavity and how is it and the bone moulded?

Answer 9

Osteoclasts located in the endosteum break down the bone and make sure that the bone does not get too wide, and also form the medullary cavity which is filled with red marrow in children and yellow marrow (fats) in adults.

Question 10

How is osteoporosis caused?

Answer 10

• Ageing loss of oestrogen (as oestrogen is important for maintaining bone volume).
• Lack of exercise, nutrients. (low peak bone mass bank).

Question 11

What are the effects of Osteoporosis on types of bones.

Answer 11

Osteoporosis occurs when osteoclasts overtake osteoblasts and so more bone is being destroying than being made (imbalance of OB and OC activity). This causes compact bone to become thinner and porous, and cancellous bone to lose volume, which results in things such as vertebrae compression fractures etc.

Question 12

Explain the 4 stages involved after a fracture occurs.

Answer 12

Stage 1:

• formation of haematoma (solid blood clotting)
• Blood vessels bring in phagocytes which are responsible for getting rid of the debris (bits of broken bone).

Stage 2:
- Fibroblasts which are brought to the site of fracture via blood vessels start forming collagen fibres.

• These fibroblasts then differentiate into chondroblasts and start forming cartilage.
• Chondroblasts form a fibrocartilaginous callus, which is made up of cartilage and forms around the area of fracture.

Stage 3:
- Osteoblasts come to the site of fracture and turn the cartilaginous callus into a bony callus.

Stage 4:

• Osteon (compact bone) arrangement is remodelled through cellular activity.

Question 13

List and describe the 3 types of bone fractures.

Answer 13

• Closed, simple - Doesn’t affect soft tissue that much, doesn’t break through the skin (minimal bone displacement).
• Open, Compound - Bone thrusts through all the soft tissue and protrudes outside of the body (this brings the risk of the bone being exposed to bacteria and getting infected).
• Greenstick - fractures that have completely separated the bone from each other.