Lecture 17: Bone Flashcards
What are the primary functions of the skeleton
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
Bone is a composite material of two things, what are they?
- Meshwork of collagen fibres: soft, flexible, resistant to lengthening
- resistance to tension - Crystals of hydroxyapatite (calcium phosphate)
- extremely hard but brittle
- resistant to compression
How is bone constantly being remodelled
Bony units- osteons- laid down by osteoblasts; maintained by osteocytes; eaten away by osteoclasts
What are osteoblasts
They lay down the organic matrix osteons which then becomes mineralised to form bone
-full mineralization may take weeks or months
What are osteocytes?
= osteoblasts entombed by mineralised matrix
- regulate mineral flux in matrix under hormonal control
- respond to stresses in bone to control remodelling (ie signals osteoclasts)
What are osteoclasts?
Large multinucleated cells
- break down calcified matrix
- eroded surface attracts osteoblasts and the cycle repeats
When loaded, stress/strain line are concentrated to the outermost parts. True or false
True!
What is wolffs law?
The architecture of bone is dictated by the stresses acting apon it
Bone shape
What are the different kind of loads bone can have?
Symmetrical load (pure compression)
Asymmetrical load
Asymmetrical force
Refer to lecture slides for pictures