cartilage and bone Flashcards
what are the 2 bone types (macroscopic)
> cortical compact bone
> cancellous spongy bone
what is cortical compact bone like
thick, hard looking
dense outer plate
80-85% of skeleton
what is cancellous spongy bone like
internal trabecular scaffolding
(to save weight)
15-20% of skeleton
what does cortical bone have
nutrient canals
what is found in the nutrient canals of cortical bone
blood vessels
they are vascularised
what is cortical bone lining tooth sockets penetrated by
bundles of collagen fibres of PDL (sharpeys fibres)
this bone is also called bundle bone
what does vital bone contain
blood vessels
what is the composition of bone by weight
> 60% inorganic
- hydroxyapatite
> 25% organic - collagen (90%) - glycoproteins § osteocalcin § osteonectin § osteopontin § sialoproteins - proteoglycans (GAGs) § chondroitin SO4 § heparan SO4
> 15% water
what are the different proteins in the composition of bone important in
bone regeneration due to periodontal disease or resorption of bone
what is in the extracellular matrix
> ground substance
> fibres (reinforce the extracellular ground substance)
what is found in the ground substance of extracellular matrix
> semi fluid gel > long polysaccharide molecules > GAGs = Glycos-amino-glycans - hyaluronic acid - proteoglycans § chondroitin sulphate § dermatan sulphate § heparan sulphate § keratan sulphate
what fibres are found in the extracellular matrix
> collagen
elastin
other non-collagenous proteins
what are the types of bone (microscopic)
> woven bone
> lamellar bone
describe woven bone
> rapidly laid down > irregular deposition of collagen > present in foetus (callus) > lots of woven bone in fractures > Contains many osteocytes
describe lamellar bone
> laid down more slowly > collagen fibres laid down in parallel > more organised bone > normal form in adult > contain fewer osteocytes
what is compact bone structure
> laid down in concentric lamellae (lamellar bone)
form longitudinal columns
organised in haversian systems around central (haversian) canal
lateral (volkman’s) canals
canals contain blood vessels
haversian system is also called an osteon
small dark lacunae (spaces) have radiating canaliculi = small canals (some linke adjacent to haversians systems = osteons)
lol this made no sense to me either sorry x
what are radiating canaliculi
interconnecting osteocyte processes
what is an important function of osteocytes
nutrition
what do osteocytes have
interconnecting projections
what is in cancellous bone
> network of thin trabeculae > trabeculae consist of lamellae > osteocytes present > no obvious haversian systems > the bone is thin > nutrients can diffuse in > bone marrow present in the spaces between trabeculae
where do osteoblasts lie
on surface of bone
where are osteoblasts derived from
mesenchymal stem cells
what do osteoblasts do
synthesis and secrete collagen fibres forming a matrix
the matrix is mineralised by calcium salts
what are osteocytes
osteoblasts that become trapped in mineralised bone
where do osteocytes lie
within spaces - lacunae
how do osteocytes contact other osteocytes
via cytoplasmic processes that run in canaliculi
what side do canaliculi radiate
one side
the side with nutrient so towards the PDL
what are osteoclasts
large, multinucleate cells
where are osteoclasts derived from
haemopoietic stem cells
related to macrophages
what do osteoclasts do
resorb bone (acid phosphates)
where do osteoclasts lie
in concavities in bone
in howship’s lacunae
what is bone remodelling
removal and replacement of bone tissue without change in overall shape (changes within, bone doesnt stay the exact same its whole life - constant turnover)
resorption balanced by deposition / apposition
what is bone remodelling controlled by
osteoblasts
what is bone remodelling regulated by
> hormones eg parathyroid hormone, calcitonin
> paracrine - various cytokines
what are the advantages of bone turnover
calcium is kept in low concentration in cells and used in important processes
where is the main storage of calcium
in bones
how much calcium can an organism maintain
2-4mmol of calcium concentration
explain bone turnover
> parathyroid hormone acts on cells to produce collagenase
> stimulates these cells to aggregate to form osteoclasts
- these then work to remove bone
> cells from osteoclasts destruction become active osteoblasts to lay down new bone
> osteoid (matrix) is formed under osteoblasts
what are signalling molecules involved in bone turnover
- various cytokines
- growth factors
what is the reversal line?
a scalloped edge on histology pictures which shows where bone resorption changes to bone deposition
what does tooth movement require
remodelling of adjacent soft and hard tissues
when does tooth movements occur
> during eruption
post-eruptive eg mesial dirft
orthodontic forces
explain orthodontic treatment briefly
- resorption in one area
- replacement in another
- allows teeth to move
- both resoprtion and depositon working at same time in different regions
- force in certain direction
- goal = remodelling
what is cartilage
semi-rigid, unmineralised connective tissue
several different types
what is the matrix of cartilage like
similar to bone
- ground substance
- fibres
- dont have mineralised content
what is hyaline cartilage
> wide spread
found in larynx, nasal septum, ends of ribs (costal cartilages) articular surfaces, embryonic skeleton (precursor to bone)
flexible
what is fibrocartilage
> found in intervertebral discs, pubis symphysis
allows a certain level of flexibility
pubis can detach during labour and reattach
where is elastic cartilage found
found in external ear, epiglottis and eustachian tube
what are cartilage cells formed by
chondroblasts
what happens to chondroblasts when they get trapped in matrix
become chondrocytes
are cartilage cells vascular?
no
they are avascular
nutrients diffuse in
some channels are present in thick areas of cartilage
what do chondrocytes contain
stores of lipid, glycogen
what happens in endochondral ossification
happens in long bones
cartilage precursor
cartilage proliferation
cartilage replaced with bone
what happens in intramembranous ossification
growth of bone onto membrane without cartilage
flat bones = skull bones
bone formed de novo in connective tissue
no cartilage precursor
what areas dont have high amounts of calcium
hands
feet
joints
there is no calcification in these areas
what do areas of no calcification allow during growth
elongation of bone
where does cartilage proliferation and growth occur
at the epiphyses of bones
how does elongation of bones occur
through endochondral ossification
what is spheno-occipital synchondrosis
bone forms around cartilage
bone has endochondral and intramembranous
what is achondroplasia
genetic defect of cartilage growth
endochondral bone growth is impaired
elongation of bones does not occur
= shorter arms and legs
intramembranous bone growth is not affected
skull proportionally looks normal but the face looks too small for the skull
base of skull reduced as it is both endochondral and intramembranous
affects arrangement of teeth = maxillary crowding
through what method does the condylar cartilage develop in the TMJ development
endochondral ossification
condyle lies in eminence
changes shape as we grow and is rearranged as we grow our teeth
what are the 3 most important areas for remodelling throughout lives
> angular process
alveolar process
coronoid process
(coronoid and angular proccesses associated with pterygoid muscles so need to grow as muscles do)
where does the condyle lie
in the articular eminence
what is the structure of the TMJ
> articular disc > articular zone > proliferative zone > fibrocartilaginous zone > calcified cartilage > subarticular bone
what can happen the alveolar and angular processes after tooth loss
these can be resorbed
changes as it opens
reduction in these areas
how is a denture kept in place manually
through suction
needs sealed surfaces to minimise lateral forces near that
sealing achieved by making it tight against the mucosa
what is resorbed after tooth loss
alveolar bone
