what are the two types of bone known as?
- cortical (compact) bone
- cancellous (spongy) bone
what % of the skeleton does cortical bone make up?
80-85% of skeleton
what % of skeleton does cancellous bone make up?
15-20% of skeleton
what type of bone is the dense outer plate of bone composed of?
cortical bone
what type of bone is the internal trabecular scaffolding composed of?
cancellous bone
what is interesting about the cortical bone found in the alveolar bone?
- cortical bone has nutrient canals that contain blood vessels
what occurs in the cortical bone lining tooth sockets?
the cortical bone lining tooth sockets is penetrated by bundles of collagen fibres of PDL (Sharpey’s fibres)
what is the compositional makeup of bone (by weight)?
- 60% inorganic (hydroxyapatite)
- 25% organic (collage, glycoproteins, proteoglycans)
- 15% water
what is the extracellular matrix?
- semi-fluid gel
- composed of long polysaccharide molecules
- also made up of glucose-amino-glycans (GAGs)
- contains fibres
what are the main fibres found within the extracellular matrix?
- collagen
- elastin
what can extracellular matrix also be referred to as?
ground substance
what are examples of glycols-amino-glycans?
- hyaluronic acid
- proteoglycans
what are the different structures of bone?
- woven bone
- lamellar bone
what is woven bone?
- rapidly laid down bone
- irregular depostion of collagen
- present in foetus
- fracture repair
- contains many osteocytes
what is lamellar bone?
- bone laid down more slowly
- collagen fibres are laid down in parallel
- normal form in adults
- contains fewer osteocytes
what bone structure contains more osteocytes, woven or lamellar?
woven bone
explain the structure of compact bone & how it is laid down?
- laid down in concentric lamellae
- forms longitudinal columns
- organised in Haversian systems around central canal
- contains lateral Volkman’s Canals
- canals contain blood vessels
what is a Haversian system also known as?
an osteon
how can the structure of cancellous bone be described when it is formed?
- network of thin trabeculae
- trabeculae consist of lamellae
- osteocytes present
- no obvious Haversion systems
- the bone is thin
what can occur in cancellous bone due to it being thin?
nutrients can diffuse in
where are osteoblasts located on bone?
lie on surface of bone
what cells are osteoblasts derived from (embryologically)?
mesenchymal cells
what is the function of osteoblasts?
synthesise & secrete collagen fibres forming a matrix which is then mineralised by calcium salts
where are osteocytes located?
lie within lacunae spaces
