Lecture 17: Bone

Question 1

What are the primary functions of the skeleton

Answer 1

Support the body
Model body shape and form
Provide a system of levers for locomotion
Protects soft parts and collapsible body cavities

The skeleton has secondary roles in:

• mineral reserves-calcium and phosphates
• acid base homeostasis

Question 2

Bone is a composite material of two things, what are they?

Answer 2

1. Meshwork of collagen fibres: soft, flexible, resistant to lengthening
   - resistance to tension
2. Crystals of hydroxyapatite (calcium phosphate)
   - extremely hard but brittle
   - resistant to compression

Question 3

How is bone constantly being remodelled

Answer 3

Bony units- osteons- laid down by osteoblasts; maintained by osteocytes; eaten away by osteoclasts

Question 4

What are osteoblasts

Answer 4

They lay down the organic matrix osteons which then becomes mineralised to form bone
-full mineralization may take weeks or months

Question 5

What are osteocytes?

Answer 5

= osteoblasts entombed by mineralised matrix

• regulate mineral flux in matrix under hormonal control
• respond to stresses in bone to control remodelling (ie signals osteoclasts)

Question 6

What are osteoclasts?

Answer 6

Large multinucleated cells

• break down calcified matrix
• eroded surface attracts osteoblasts and the cycle repeats

Question 7

When loaded, stress/strain line are concentrated to the outermost parts. True or false

Answer 7

True!

Question 8

What is wolffs law?

Answer 8

The architecture of bone is dictated by the stresses acting apon it

Question 9

Bone shape

What are the different kind of loads bone can have?

Answer 9

Symmetrical load (pure compression)
Asymmetrical load
Asymmetrical force
Refer to lecture slides for pictures