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Bone Response to Damage (view source)
Revision as of 14:57, 28 September 2007
, 14:57, 28 September 2007no edit summary
***Mesenchymal cells
***Mesenchymal cells
***Arise from bone marrow stroma
***Arise from bone marrow stroma
***Produce bone matrix = '''osteoid'''
***Produce bone matrix = '''osteoid''' - uncalcified
***Cell membranes are rich in alkaline phosphatase (ALP)
***Cell membranes are rich in alkaline phosphatase (ALP)
***Promoted by growth factors
***Plump, cuboidal basophilic cells
**'''Osteocytes'''
**'''Osteocytes'''
***Osteoblasts that have become surrounded by mineralised bone matrix
***Osteoblasts that have become surrounded by mineralised bone matrix
***Occupy cavities called '''lacunae'''
***Occupy cavities called '''lacunae'''
**'''Osteoclasts'''
**'''Osteoclasts'''
***Multinucleated cells
***Large, often multinucleated cells
***Acidophilic cytoplasm
***Derived from haematopoietic stem cells
***Derived from haematopoietic stem cells
***Responsible for bone resorption (have a brush border for this)
***Responsible for bone resorption (have a brush border for this)
*'''Matrix'''
***Sit in bone surface depression - '''Howship's lacuna'''
**Type I collagen forms the backbone of the matrix
*'''Matrix''':
**Mineral – accounts for 65% of bone and includes Ca, P, Mg, Mn, Zn, Cu, Na
**Osteoid
***Type I collagen forms the backbone of the matrix (90%)
***Non-collagenous protein forming amorphous ground substance (10%)
**Mineral
***Crystalline lattice of calcium phosphate and calcium carbonate
***Also contains Mg, Mn, Zn, Cu, Na, F
***Accounts for 65% of bone
===Bone organisation===
===Bone organisation===
*****Forms the shell of long bone shafts - contain [[Haversian systems]]
*****Forms the shell of long bone shafts - contain [[Haversian systems]]
****'''Cancellous bone''' (spongy or trabecular)
****'''Cancellous bone''' (spongy or trabecular)
*****Made up of plates, tubes or bars arranged in lines of stress
*****In vertebrae, flat bones and epiphyses of long bones
*****In vertebrae, flat bones and epiphyses of long bones
*****Contains no Haversian systems
*****Contains no Haversian systems
*Inner layer
*Inner layer
**Merges with the outer layer of bone
**Merges with the outer layer of bone
**Contains osteoblasts and osteoprogenitor stem cells
**Contains osteoblasts and osteoprogenitor stem cells in young animals and in adults with fractures or disease
*Damage to the periosteum invokes a hyperplastic reaction of the inner layer
*Damage to the periosteum invokes a hyperplastic reaction of the inner layer
*The blood supply to the mature bone enters via the periosteum
*The blood supply to the mature bone enters via the periosteum
*'''Endosteum''' lines the marrow cavity