Bones

Question 1

Give four functions of bone and an example of each

Answer 1

Mechanical - support and attachment for muscles, tendons, ligaments and joints

Protective - protects internal organs

Metabolic - mineral reservoir for calcium and phosphate homeostasis

Haematopoiesis - support blood formation

Question 2

Describe the development of bone as a result of endochondral ossification

Answer 2

• bone forms as cartilage first during third month of development
• blood vessels and osteogenic cells invade the cartilage framework
• the cartilage remains as growth plates
• growth plates fuse at approx. 18 in females and 21 in males

Question 3

Describe the development of bone as a result of intramembranous ossification

Answer 3

• bone forms as a fibrous plate
• bone cells differentiate from fibroblasts and haemopoietic precursers
• no cartilaginous phase

Question 4

Describe the composition of bone

Answer 4

• 20% water
• 35% protein - collagen type I (provides toughness), growth factor proteins, other organic matrix proteins
• minerals - hydroxyapatite (provides rigidity)

Question 5

The epiphyses of long bones are composed of

Answer 5

trabecular (spongy) bone - acts as a softer interface at joints

Question 6

The diaphysis of long bones is made up of

Answer 6

cortical bone

Question 7

Cortical bone is

Answer 7

• denser
• arranged into Haversian Systems from the way the collagen molecules form fibrils which then form fibres and finally sheets
• structure gives the bone its strength

Question 8

Give the two main cells involved in bone maintenance and renewal

Answer 8

• osteoclasts

- osteoblasts

Question 9

Osteoclasts are

Answer 9

• the bone resorbing cells

- derived from haemopoietic lineage

Question 10

Osteoblasts are

Answer 10

• responsible for laying down more come

- derived from mesenchymal lineage

Question 11

Bones are constantly monitored and remodelled to

Answer 11

keep them at peak strength

Question 12

Osteoclasts will absorb any area of bone that has been

Answer 12

damaged

Question 13

When damaged areas of bone have been absorbed, osteoblasts will

Answer 13

lay down new bone in the same area

Question 14

Osteocytes act as sensors of

Answer 14

mechanical pressure and damage