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BDS2 BAMS > bone and cartilage > Flashcards

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
Q

what are osetoclasts?

A

Large, multinucleate cells, derived from haemopoietic stem cells

26
Q

what cell type are osteoclasts related to?

A

macrophages

27
Q

what do macrophages do?

A

aggregate for defence function of engulfing and removing material from tissue

28
Q

what do osetoclasts do?

A

resorb bone (acid phosphatases)

29
Q

where do osteoclasts lie?

A

lie in concavities in bone

- Howship’s lacunae

30
Q

what is the logic of bone remodelling (turnover)?

A

Removal and replacement of bone tissue, without change in overall shape

Resorption balanced by deposition (apposition).

31
Q

how much cortical bone is replaced each year?

A

2%

32
Q

how much cancellous bone is replaced each year?

A

25%

33
Q

what controls bone remodelling?

A

osteoblasts

34
Q

what regulates bone remodelling?

A
  • hormones (e.g. parathyroid hormone, calcitonin)

- Paracrines (various cytokines)

35
Q

what are the advantages of bone remodelling?

A
  • 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
Q

process of bone remodelling

A

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
Q

how can bone remodelling be used to dentist advantage?

A

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
Q

what is the reversal line?

A

Scalloped edge shows where bone resorption changes to bone deposition.

39
Q

what does tooth movement require?

A

require remodelling of adjacent soft and hard tissues

40
Q

when does remodelling of adjacent soft and hard tissues occur?

A
  • 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
Q

describe cartilage

A

Semi-rigid, unmineralised connective tissue

several different types of cartilage

42
Q

cartilage matrix

A

similar to bone

  • Ground substance
  • Fibres (see earlier)
  • No mineral content

several different types of cartilage

43
Q

hyaline cartilage locations

A

Widespread
- Larynx, nasal septum, trachea, ends of ribs (costal cartilages), articular surfaces, embryonic skeleton (precursor to bone)

flexible

44
Q

fibrocartilage locations

A

Intervertebral discs, pubic symphysis
- Allows pubic to detach and reattach when giving birth

Need remodelling but need certain level of flexibility

45
Q

elastic cartilage locations

A

External ear, epiglottis, Eustacian tube

46
Q

what forms cartilage cells?

A

Formed by chondroblasts

- These get trapped the matrix and become chondrocytes

47
Q

is cartilage vascularised?

A

no, it is avascular

if cutting tissue and have no bleeding = cartilage

48
Q

how does cartilage get nutrients?

A

Nutrient diffuses in

Some channels are present in thick areas of cartilage

Chondrocytes contain energy stores of lipid, glycogen

49
Q

what are 2 key bone growth processes?

A
  • endochondral ossification

- intramembranous ossification

50
Q

what does endochondral ossification require?

A

presence of cartilage

  • Long’ bones
  • Cartilage precursor
  • Cartilage proliferation
  • Cartilage replaced with bone
51
Q

where does intramembranous ossification requrie?

A
  • ‘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
Q

process of bone growth in the skull

A

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
Q

process of endochondral ossification

A

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
Q

what occurs at spheno-occipital synchondrosis?

A

Skull can have intramembranous as of spaces (foramina)

Base of skull needs elongation
- Needs endochondral ossification (sphenoid (needs lateral and longitudinal growth))

55
Q

what is achondroplasia?

A
  • Genetic defect of cartilage growth
  • Endochondral bone growth is impaired. Intramembranous bone growth is unaffected.

e.g. Eleanor (Ellie) Simmonds

56
Q

how does the bone develop at the TMJ?

A

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
Q

3 key parts of the mandible

A
  • 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
Q

what happens to edentulous jaws?

A

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
Q

what are the characteristics and functions of the angular and coronoid processes?

A
  • associated with muscles

- weaker and less force

60
Q

what must happen if the alveolar bone resorbs?

A

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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