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bone and cartilage Flashcards

1
Q

2 types of bone

A
  • cortical, compact bone

- cancellous, spongy bone

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2
Q

cortical, compact bone is

A
  • dense outer plate

- 80-85% of skeleton

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3
Q

cancellous, spongy bone is

A
  • internal trabecular scaffolding

- 15-20% of skeleton

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4
Q

in alveolar bone what type of bone lines tooth sockets?

A

cortical

it is penetrated by bundles of collagen fibres of PDL (Sharpey’s fibres)

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5
Q

what is in the cortical alveolar bone?

A

nutirent canals (contains BVs)

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6
Q

composition of bone by weight

A

60% inorganic (HA)
15% water
25% organic

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7
Q

what makes up the 25% organic portion of bone?

A

gylcoproteins

  • Osteocalcin
  • Osteonectin
  • Osteopontin
  • Sialoproteins

proteoglycans

  • Chondroitin SO4
  • Heparan SO4
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8
Q

compare dentine and bone constituents

A

dentine has a lower inorganic and higher water and organic component

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9
Q

what are the types of bone resorption you can get in the oral cavity

A

vertical and horizontal

Vertical resorption of bone can maybe grow bone to have more attachment between bone and tooth
- Trying to regenerate periodontal tissue

Osteocalcin and Osteonectincan be added to regions to help regenerate

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10
Q

what is the characteristics of the extracellular matrix?

A

“Ground substance” and fibres

  • Semi-fluid gel
  • Long polysaccharide molecules
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11
Q

what makes up the extracellular matrix?

A

Glycos-amino-glycans (GAGs)
- Hyaluronic acid
- Proteoglycans
(Chondroitin sulphat; Dermatan sulphate; Heparan sulphate; Keratan sulphate)

Fibres (reinforce extracellular ground substance):

  • Collagen
  • Elastin
  • Other non-collagenous proteins
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12
Q

2 microscopic types of bone

A

woven

lamellar

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13
Q

woven bone properties

A
  • rapidly laid down
  • Irregular deposition of collagen
  • present in fetus,
  • fracture repair (callus)
  • contains many osteocytes

important for forensics for recognising fractures

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14
Q

lamellar bone properties

A
  • laid down more slowly (Well organised_
  • Collagen fibres laid down in parallel
  • normal form in adult
  • contains fewer osteocytes
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15
Q

compact bone histology

A
  • Laid down in concentric lamellae (lamellar bone)
  • Form longitudinal columns
  • Organised in Haversian systems around central (Haversian) canal
  • Lateral (Volkman’s) canals linking 2 Haversian systems
  • Canals contain blood vessels
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16
Q

what are lacunae?

A

= small canals

  • Radiating osteocytes
  • Some canaliculi link adjacent Haversian systems
  • Nutrition and communication
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17
Q

cancellous bone properties

A
  • Network of thin trabeculae
  • Trabeculae consist of lamellae
  • Osteocytes present
  • No obvious Haversian systems
  • The bone is thin, and nutrients can diffuse in
  • Bone marrow present in the spaces between trabeculae
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18
Q

osteoblasts lie….

A

on surface of bone

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19
Q

what did osteoblasts derive from?

A

mesenchymal stem cells

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20
Q

what do osteoblasts do?

A

Synthesise and secrete collagen fibres forming a matrix

The matrix is mineralised by calcium salts
- When not mineralised it is an osteon

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21
Q

osteocytes are

A

become trapped in mineralised bone

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22
Q

where do osteocytes lie?

A

lie within lacunae (spaces)

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23
Q

how to osteocytes contact each other?

A

via cytoplasmic processes that run in canaliculi
- Allows communication between

Osteocytes also appear to communicate with osteoblasts

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24
Q

how do differentiate histologically between dark spaces in cementum and osteocytes in bone?

A

Most of the time don’t see canaliculi in cementum

  • If you do then will only radiate unidirectionally towards periodontal ligament (vascularised, nutrient source)
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25
what are osetoclasts?
Large, multinucleate cells, derived from haemopoietic stem cells
26
what cell type are osteoclasts related to?
macrophages
27
what do macrophages do?
aggregate for defence function of engulfing and removing material from tissue
28
what do osetoclasts do?
resorb bone (acid phosphatases)
29
where do osteoclasts lie?
lie in concavities in bone | - Howship’s lacunae
30
what is the logic of bone remodelling (turnover)?
Removal and replacement of bone tissue, without change in overall shape Resorption balanced by deposition (apposition).
31
how much cortical bone is replaced each year?
2%
32
how much cancellous bone is replaced each year?
25%
33
what controls bone remodelling?
osteoblasts
34
what regulates bone remodelling?
- hormones (e.g. parathyroid hormone, calcitonin) | - Paracrines (various cytokines)
35
what are the advantages of bone remodelling?
- Calcium in low concentration in cell (used in number of essential events) - Main store in bones - Way organism maintains 2.4mmolar Ca for essential functions - Always changing
36
process of bone remodelling
PTH acting on cell to promote collagenase production Cells will join together to form osteoclasts, PTH stimulates aggregation Osteoblasts become active to form osteoid matrix
37
how can bone remodelling be used to dentist advantage?
Used to our advantage - Speed up resorption - Speed up rebuilding of Ca at another site Could move teeth (apoptosis in front and rebuild behind) - Orthodontic treatment (osteoclasts in a targeted region; osteoblasts in a targeted region) - Drifting of teeth
38
what is the reversal line?
Scalloped edge shows where bone resorption changes to bone deposition.
39
what does tooth movement require?
require remodelling of adjacent soft and hard tissues
40
when does remodelling of adjacent soft and hard tissues occur?
- during eruption (Resorption of crypt where tooth was, resorption for root formation, deposition to cover root) - post-eruptive (e.g. mesial drift) - orthodontic forces
41
describe cartilage
Semi-rigid, unmineralised connective tissue several different types of cartilage
42
cartilage matrix
similar to bone - Ground substance - Fibres (see earlier) - No mineral content several different types of cartilage
43
hyaline cartilage locations
Widespread - Larynx, nasal septum, trachea, ends of ribs (costal cartilages), articular surfaces, embryonic skeleton (precursor to bone) flexible
44
fibrocartilage locations
Intervertebral discs, pubic symphysis - Allows pubic to detach and reattach when giving birth Need remodelling but need certain level of flexibility
45
elastic cartilage locations
External ear, epiglottis, Eustacian tube
46
what forms cartilage cells?
Formed by chondroblasts | - These get trapped the matrix and become chondrocytes
47
is cartilage vascularised?
no, it is avascular if cutting tissue and have no bleeding = cartilage
48
how does cartilage get nutrients?
Nutrient diffuses in Some channels are present in thick areas of cartilage Chondrocytes contain energy stores of lipid, glycogen
49
what are 2 key bone growth processes?
- endochondral ossification | - intramembranous ossification
50
what does endochondral ossification require?
presence of cartilage - Long’ bones - Cartilage precursor - Cartilage proliferation - Cartilage replaced with bone
51
where does intramembranous ossification requrie?
- 'Flat’ bones - Bone formed de novo in C.T. (connective tissue) - No cartilage precursor - Skull and Face growth growth of bone onto membranous tissue without cartilage
52
process of bone growth in the skull
Skull has high Ca in some areas and some less - Concentrated in specific areas Spaces in between parts of skull allow Intramembranous – foramina - vault of skull
53
process of endochondral ossification
Initially, a cartilage skeleton is laid down. The cartilage is replaced with bone. - There are several centres of ossification. - Starts to ossify at the centre ``` Cartilage proliferation (and growth) occurs at the epiphyses - Ossification centre going out from diaphysis to epiphysis when bone is finalised ``` Dynamic process
54
what occurs at spheno-occipital synchondrosis?
Skull can have intramembranous as of spaces (foramina) Base of skull needs elongation - Needs endochondral ossification (sphenoid (needs lateral and longitudinal growth))
55
what is achondroplasia?
- Genetic defect of cartilage growth - Endochondral bone growth is impaired. Intramembranous bone growth is unaffected. e.g. Eleanor (Ellie) Simmonds
56
how does the bone develop at the TMJ?
Endochondral calcification at condylar cartilage - Condyle lies inside articular eminence Allows cartilage to grow, remodel and reshape if necessary - Change shape as we are born - Rearrangement when we grow and lose teeth
57
3 key parts of the mandible
- Alveolar process - can be removed or disappears - Angular process - Coronoid Important in remodelling throughout life due to Insertion of muscles (angular and coronoid) and teeth presence (alveolar)
58
what happens to edentulous jaws?
alveolar process has been resorbed after tooth loss Minimised coronoid process, angular and alveolar all changed shape - Reduction of areas - Not fully closed appearance
59
what are the characteristics and functions of the angular and coronoid processes?
- associated with muscles | - weaker and less force
60
what must happen if the alveolar bone resorbs?
resorbs if edentulous - Need to put denture Dentures held simply through suction - Need to keep a sealed surface near the borders Minimise lateral forces - denture cusps are not as prevalent as in real teeth - so less movement. Keep close to lining mucosa - Maxilla easier as palate there - Tongue can force denture out of mandible - Difficult arrangement if no seal

BDS2 BAMS (54 decks)

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