Bone physiology

Question 1

List the functions of the skeleton

Answer 1

• Structural
• Protection
• Locomotion
• Mineral reservoir

Question 2

What are the 4 types of bone?

Answer 2

Long- e.g. femur
Short- e.g. tarsal and carpal
Flat- e.g. pelvis
Irregular -e.g. vertebrae

Question 3

in older animals what prevents the marrow compounds being released effectively?

Answer 3

-Adipose tissue

Question 4

State the 3 sections of the bone

Answer 4

• Diaphysis (shaft)
• Metaphysis (between the end and middle)
• Epiphysis (end)

Question 5

What are the two types of bone structure?

Answer 5

• Cortical (compact)

- Cancellous (trabecular)

Question 6

What is osteoid?

Answer 6

-Ground substance in which numerous collagen fibres are embedded. It is synthesised by the osteoblasts and secreted onto existing bone surface

Question 7

Which cells do osteoblasts develop from?

Answer 7

Mesenchymal stem cells

Question 8

Describe the organic component of bone matrix

Answer 8

-Osteoid:
Collagen type 1
Glycoproteins (bind collagen and mineral)
Proteoglycans (bind growth factor)
Bone sialoproteins (associated with cell adhesion)

Question 9

Which mineral crystals are found in the bone matrix (inorganic component)?

Answer 9

• Hydroxyapatite
• Carbonate
• Calcium phosphate

Question 10

When does mineralisation occur?

Answer 10

As soon as osteoid is secreted

Question 11

Discuss the organisation of collagen fibres in bone

Answer 11

• They are orientated in different directions
• Woven bone= occurs in young growing animals and fracture repair sites
• Lamellar bone= thin layers of osteoid, collagen fires are parallel.

Question 12

Describe osteocytes

Answer 12

• They are scattered within matrix
• Interconnected by dendritic processes
• Reside within ‘lacunae’ which are interconnected by canaliculi
• Long life span
• Help to maintain the matrix

Question 13

Describe osteoclasts

Answer 13

-Responsible for bone resorption
-They are LARGE cells with multiple nuclei
-Release protons to create an acidic environment resulting in demineralisation
-Also secrete proteases to destroy organic matrix
Derived from bone marrow

Question 14

List the metabolic functions of bone

Answer 14

• Mineral storage (mainly phosphorus and calcium)
• Growth factor storage (IGF)
• Fat storage (in yellow marrow)
• Acid/ base balance
• Detoxification (stores heavy metals)

Question 15

How does bone help buffer the bloods acid/ base balance?

Answer 15

It either absorbs or releases alkaline salts

Question 16

Describe the role of bone as an endocrine organ

Answer 16

• It controls phosphate metabolism by releasing fibroblast growth factor 23
• Bone cells also release a hormone called osteocalcin]

Question 17

What does osteocalcin do?

Answer 17

increases both the insulin secretion and sensitivity.

Question 18

Which hormones are involved in the increasing of osteoid levels?

Answer 18

Growth hormone, thyroid hormone and sex hormones

Question 19

How do osteoblasts promote the reabsorption of bone?

Answer 19

-Secrete cytokines by stimulating osteoclast activity

Question 20

What inhibits osteoclast activity?

Answer 20

Calcitonin and osteoprotegerin