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***Promoted by growth factors
 
***Promoted by growth factors
 
***Have receptors for PTH
 
***Have receptors for PTH
 +
****They contract in response -> space for osteoclasts to attach
 
**'''Osteocytes'''
 
**'''Osteocytes'''
 
***Osteoblasts that have become surrounded by mineralised bone matrix
 
***Osteoblasts that have become surrounded by mineralised bone matrix
Line 41: Line 42:  
***Regulate composition of bone fluid
 
***Regulate composition of bone fluid
 
**'''Osteoclasts'''
 
**'''Osteoclasts'''
***Large, often multinucleated cells  
+
***Histologically:
***Acidophilic cytoplasm
+
****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
 +
****Firstly dissolve mineral followed by collagen
 +
****Use brush border for this
 
***Sit in bone surface depression - '''Howship's lacuna'''
 
***Sit in bone surface depression - '''Howship's lacuna'''
 +
***Do <u>not</u> have receptors for PTH
 +
***Have receptors for calcitonin
 +
****Involute their brush border in response
 +
****Detach from bone surface
 
*'''Matrix''':
 
*'''Matrix''':
 
**Osteoid
 
**Osteoid
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