Bone and Cartilage Flashcards
what are the 2 types of bone?
cortical, compact bone and cancellous, spongy bone
where is the cortical bone?
it is the dense outer plate
where is the cancellous bone?
it is the internal trabecular scaffolding
what is the alveolar bone structure like?
cortical bone which has nutrient canals containing blood vessels
what is the cortical bone lining of the alveolar bone penetrated by?
bundles of collagen fibres of PDL
what does the inorganic component of bone consist of?
hydroxyapatite
what does the organic component of bone consist of?
collagen, glycoproteins, proteoglycans
what is ground substance
semi fluid gel made of long polysaccharide molecules and glycos-amino-glycans
which types of GAGs make up the ground substance?
hyaluronic acid, proteoglycans
what are the proteoglycans in bone?
chondroitin sulphate, dermatan sulphate, heparan sulphate, keratan sulphate
what is the function of the fibres in the extracellular matrix?
to reinforce extracellular ground substance
what types of fibres are found in the ECM?
collagen, elastin and other non-collagenous proteins
microscopically, what are the different types of bone (not cortical/cancellous)
woven and lamellar
what is woven bone and where is it present?
irregular deposition of collagen present in foetus and fracture repairs
what type of cell does woven bone have many of?
osteocytes
which type of bone is rapidly laid down?
woven bone
what is lamellar bone and where is it present
collagen fibres laid down in parallel in adults
what type of bone is laid more slowly?
lamellar bone
what type of bone contains fewer osteocytes?
lamellar bone
what type of structure is compact bone laid down in?
concentric lamellae which forms longitudinal columns
what type of system is compact bone organised in?
haversian systems around a central haversian canal
what type of canals link the Hversian canals?
Volkmans canals
what do the canals contain
blood vessels
what are Haversian systems also called?
osteons
what does an osteon look like?
central small lacunae with radiating canaliculi (small canals)
what is cancellous bone
a network of thin trabeculae
what do trabeculae consist of?
lamellae
does cancellous bone have a Haversian system?
no
instead of having a Haversian system how do nutrients get about cancellous bone?
the bone is thin so the nutrients can diffuse in
what is present between trabeculae?
bone marrow
where do osteoblasts lie?
on surface of bone
what are osteoblasts derived from
mesenchymal stem cells
what do osteoblasts do?
synthesise and secrete collagen fibres forming a matrix
what is the matrix secreted by osteoblasts mineralised by?
calcium salts
what are osteocytes
osteoblasts which are trapped in mineralised bone
where do osteocytes lie?
in spaces (lacunae)
how do osteocytes contact each other?
via cytoplasmic processes that run in canaliculi
what are osteoclasts?
large multinucleated cells derived from haemopoietic stem cells
what do osteoclasts do?
resorb bone
where do osteoclasts lie?
in concavities in the bone - Howships lacunae
what is bone remodelling
removal and replacement of bone tissue without change in overall shape
what percentage of cortical bone is replaced per year?
2%
what percentage of cancellous bone is replaced per year?
25%
what is bone remodelling controlled by?
osteoblasts
what is bone remodelling regulated by?
hormones (PTH, calcitonin), paracrines (cytokines)
how does bone turnover work?
PTH secretes collagenase and osteoclasts to start the process of bone resorption, osteoblasts produce osteoids whilst this is occurring
what is a reversal line?
scalloped edge which shows where bone resorption changes to bone deposition
what does tooth movement require?
remodelling of adjacent soft and hard tissues
when does tooth movement take place?
during eruption, post-eruptive (mesial drift), orthodontic forces
what is cartilage?
semi-rigid unmineralised connective tissue
what type of matrix does cartilage have?
a similar one to bone consisting of ground substance and fibres
what are the 3 types of cartilage?
hyaline cartilage, fibrocartilage and elastic cartilage
give examples of where hyaline cartilage is present
larynx, nasal septum, trachea
give examples of where fibrocartilage is present
intervertebral discs
give examples of where elastic cartilage is present
external ear, epiglottis
what are cartilage cells formed by?
chondroblasts
what do chondroblasts become once they get trapped in cartilage matrix?
chrondrocytes
what do chondrocytes contain?
stores of lipid and glycogen
what are the 2 types of bone growth?
endochondral ossification and intramembranous ossification
which type of bones use endochondral ossification
long bones of which cartilage had been laid down as a precursor
which type of bones use intramembranous ossification?
flat bones with no cartilage precursor
where does cartilage proliferation and growth occur?
at the epiphyses
which type of ossification does the spheno-occipital bone have?
both as it is the face of the skull so it does not have flexibility of the parietal, frontal and occipital bone
what type of ossification is affected by achondroplasia?
endochondral
which type of ossification does the condyle have?
endochondral as it changes shape from birth to elderly
why does the angular process of the mandible change shape?
because it needs teeth to maintain shape and if teeth are lost the bone will resorb
