65. bone tissue. cells of bone tissue Flashcards
What is bone and its function
type of connective tissue with calcified extracellular matrix
supports body, protects internal organs, contains bone marrow
what are the three main cell types
Osteocytes - found in cavities between layers of the bone matrix
Osteoblasts - which synthesize the organic components of the matrix
Osteoclasts - of Macrophage origin, giant multinucleated cell involved in bone resorption.
metabolites are unable to diffuse though calcified matrix of the bone
how does exchange happen between osteocytes and blood capillaries?
through very thin cylindrical spaces of canaliculi
what lines the internal and external surface of the bone?
internal: endosteum- contains bone marrow
external: periosteum- supplies bone with blood, nerve and cells
what are osteoblasts?
originate from mesenchymal stem cells
synthesizes and secretes organic compounds of matrix like type 1 collagen fibres, proteoglycans and glycoprotein eg osteonectin
Found at surfaces of bone matrix and forms cuboidal layer and gap junctions
osteoblasts differentiate from osteoprogenitor stem cells and secrete components of the initial matrix. What is this called
osteoid
What happens when some osteoblasts get surrounded by their own secretions?
they differentiate into osteocytes
What are osteocytes?
maintains the bone matrix until resorption of matrix
contains reduced ER and golgi and has more condensed nuclear chromatin
lies within the lacunae and uses canaliculi to communicate
What are osteoclasts?
dissolves hydroxyapatite and promotes collaged digestion
erodes bone during osteogenesis and bone remodelling
pumps out collagenase and other enzymes
How does bone become calcified?
The ECM of the bone is called osteoid tissue before calcification
once calcium and phosphate ion concentration increases, they are deposited into the ECM causing formation of hyroxyapatite crystals which calcifies the matrix
