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→Composition of Bone
*Cells:
*Cells:
**'''Osteoblasts''': single layer of cuboidal cells which synthesize bone extracellular matrix (ECM)
**'''Osteoblasts''': single layer of cuboidal cells which synthesize bone extracellular matrix (ECM)
***Basophilic cytoplasm
***When inactive - less cytoplasm -> flattened
**'''Osteocytes''': osteoblasts embedded in their own matrix; reside within '''lacunae''' and are interconnected via channels forming '''canaliculi'''
**'''Osteocytes''': osteoblasts embedded in their own matrix; reside within '''lacunae''' and are interconnected via channels forming '''canaliculi'''
***'''Canaliculi''' create connections to form a huge neural-like junctional organization
***'''Canaliculi''' create connections to form a huge neural-like junctional organization
**'''Osteoclasts''': giant (multinucleate monocytes) cells which act to resorb bone ECM
**'''Osteoclasts''': giant (multinucleate monocytes) cells which act to resorb bone ECM
**Osteoblasts, osteocytes, chondroblasts and chondrocytes are derived from stromal fibroblastic system ('''osteoprogenitor cells'''); osteoclasts from haematopoietic system
All mammalian bone is organized as lamellated sheets:
All mammalian bone is organized as lamellated sheets: