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BDS2 BAMS Oral Biology > Bone and Cartilage > Flashcards

Bone and Cartilage Flashcards

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1
Q

What are the 2 types of bone

A

cortical/compact

cancellous/spongy

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2
Q

describe cortical bone

A

Cortical bone is the dense outer layer of bone

It is compromised of structural units called osteon

Each osteon is composed of layers called lamellae

The central canal of each osteon contains nerves, capillaries and lymphatics

Forms 80-85% of the skeleton

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3
Q

describe cancellous bone

A

Contains lamellar bone – the osteocytes are housed in lacunae

Lattice like network of rods called trabeculae

Orientated to provide maximum strength for minimum mass

Spaces between trabeculae occupied by red and yellow marrow

Externally lined by endosteum

Makes up 15-20% of the skeleton

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4
Q

what are the 3 components to alveolar bone

A

An external plate of cortical bone

The inner socket wall of thin cortical bone called the alveolar bone proper

Cancellous bone (between these two compact layers)

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5
Q

what does the cancellous bone contain

A

blood vessels, nerves and lymphatics that send their branches through the cortical bone through small openings called Volkman’s canals to supply the periodontal ligament

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6
Q

what does the cortical bone lining tooth sockets penetrated by

A

bundles of collagen fibres of PDL (Sharpey’s fibres)

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7
Q

what is the composition of bone

A

60% inorganic
15% water
25% organic

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8
Q

what makes up the organic component

A

collagen (90%)
glycoprotiens
proteoglycans

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9
Q

what is the function of the proteoglycans

A

responsible for jelly structure of the matrix

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10
Q

what are the two different ways bone can be resorbed

A

horizontal

vertical

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11
Q

what is horizontal resorption

A

generalized bone loss occurs most frequently as horizontal bone loss. Horizontal bone loss manifests as a somewhat even degree of bone resorption so that the height of the bone in relation to the teeth has been uniformly decreased. It occurs in a plane parallel to the CEJs of the adjacent teeth

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12
Q

what is vertical resorption

A

occurs adjacent to the tooth and usually in the form of a triangular area of missing bone known as triangulation.

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13
Q

what is the ECM made up of

A

ground substance and fibres

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14
Q

what is ground substance

A

semi fluid gel

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15
Q

what does ground substance contain

A

long polysaccharide molecules

glycosaminoglycans

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16
Q

what are the fibres found in the ECM

A

Collagen

Elastin

Other non-collagenous proteins

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17
Q

what are the two types of microscopic bone

A

woven

lamellar

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18
Q

describe woven bone

A

rapidly laid down
irregular deposition of collagen
contains many osteocytes

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19
Q

where is woven bone found

A

fetus

fracture repair

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20
Q

describe lamellar bone

A

Laid down more slowly so well organised

Collagen fibres laid down in parallel

Normal form in adult
contains fewer osteocytes

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21
Q

what is the structure of compact bone

A

Compact bone is laid down in concentric lamellae (lamellar bone)
it forms longitudinal columns

It is organized in haversian systems around the central (Haversian canal)

There is also lateral (volkman’s) canals – these link haversian canals

The canals contain blood vessels

There are small ‘lacunae’ with radiating canaliculi

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22
Q

what is the function of the interconnecting projections of the osteocytes

A

their function is nutrition but also communication

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23
Q

describe cancellous bone

A

Cancellous bone is made up of a network of thin trabeculae

The trabeculae consist of lamellae

There are osteocytes present

There is no obvious haversian systems

The bone is thin and nutrients can diffuse in

Bone marrow is present in the spaces between the trabeculae

24
Q

describe osteoblasts

A

Lie on the surface of the bone

Derived from mesenchymal stem cells

Synthesize and secrete collagen fibres forming a matrix - matrix that is not yet mineralized is called osteoid

The matrix is then mineralized by calcium salts

25
Q

describe osteocytes

A

Osteocytes are osteoblasts that become trapped in mineralized bone

They lie within spaces called lacunae

They contact other osteocytes via cytoplasmic processes that run in canaliculi

Osteocytes also appear to communicate with osteoblasts

26
Q

how can we tell the difference between bone and cementum from osteocytes

A

We can tell the difference between cementum and bone through the osteo/cementocytes as in cementum we cannot usually see the canaliculi and if we can see them then the canaliculi are only on one side, facing the PDL as this is where the cementum’s nutrients comes from

27
Q

describe osteoclasts

A

Large, multinucleate cells derived from haemopoietic stem cells

They are related to macrophages

They resorb bone (acid phosphatases)

They lie in concavities in bone called howship’s lacunae

28
Q

what is bone remodelling controlled by

A

osteoblasts

29
Q

what i the process of bone turnover regulate dby

A

hormones - PTH, calcitonin

paracrine - various cytokines

30
Q

what happens in bone turnover

A

PTH and signaling molecules increase the number and activity of the osteoclasts – osteoclasts which will resorb bone on one side

On the other side the osteoblasts work to secrete osteoid (matrix)

31
Q

what is the reversal line

A

There is a scalloped edge which shows where the bone resorption changes to bone deposition

32
Q

what does tooth movement require

A

remodeling of adjacent soft and hard tissues

33
Q

when do tooth movements occur

A

During eruption – tooth eruption requires the resorption of the crypt where the tooth is actually present and resorption of where the root will form so that the root can take this place

Post-eruptive (e.g mesial drift)

Orthodontic forces

34
Q

what is cartilage

A

semirigid, unmineralized connective tissue

35
Q

how is cartilage similar to bone

A

Its matrix is similar to bone, made up of:

Ground substance

Fibres

36
Q

what are the 3 types of cartilage

A

hyaline
fibrocartilage
elastic

37
Q

where is hyaline cartilage found

A

Widespread (present almost everywhere)

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

38
Q

where is fibrocartilage found

A

Found in intervertebral discs, pubic symphysis

39
Q

where is elastic cartilage found

A

External ear

Epiglottis

Eustacian tube

40
Q

what is cartilage formed by

A

chondroblasts

41
Q

how is cartilage different to bone

A

avascular

42
Q

what are the two ways bone can grow

A

endochondral ossification

intramembranous ossification

43
Q

what bones are formed via endochondral classification

A

long bones

base of the skull

44
Q

what does endochondral ossification consist of

A

cartilage being replaced by bone - the cartilage serves as a template to be completely replaced by new bone

45
Q

what bones are formed via intramembranous ossification

A

flat bones

46
Q

describe intramembranous ossification

A

o Bone is formed de novo in C.T

o There is no cartilage precursor

47
Q

what are the bones of the skull formed by

A

intramembranous ossification – it forms the vault of the skull
calcification occurs between membranes

48
Q

describe endochondral ossification

A

Initially a cartilage skeleton is laid down
The cartilage is replaced with bone
There are several centres of ossification
Cartilage proliferation (and growth) occurs at the epiphyses

49
Q

What is the process of endochondral ossification

A

Mesenchymal cells differentiate into chondrocytes that produce a cartilage model of the future bony skeleton

Blood vessels on the edge of the cartilage model bring osteoblasts that deposit a bony collar

Capillaries penetrate cartilage and deposit bone inside the cartilage model forming the primary ossification centre

Cartilage and chondrocytes continue to grow at the ends of bone while medullary cavity expands and remodels

Secondary ossification centres develop after birth

Hyaline cartilage remains at growth plate and at joint surface as articular cartilage

50
Q

what is synchondrosis

A

is an almost immovable joint between bones bound by a layer of cartilage

51
Q

what is the sphenooccipital synchondrosis a major contributor to

A

post natal growth – growth at the synchondrosis lengthens this area of the cranial base and bone remodelling on surfaces is also important

52
Q

what is achondroplasia

A

It is a defect in cartilage growth

Endochondral bone growth is impaired while intramembranous bone growth is unaffected

53
Q

what does the condylar cartilage form by

A

forms by endochondral calcification

54
Q

what dissapears when teeth are extracted

A

alveolar process

55
Q

What are the steps to intramembranous ossification

A

Mesenchymal cells group into clusters, differentiate into osteoblasts and ossification centres form

Secreted osteoid traps osteoblasts which then become osteocytes

Trabecular matrix and periosteum form

Compact bone develops superficial to the trabecular bone, and crowded blood vessels condense into red bone marrow

56
Q

How does the mandible grow

A

through both endochondral and intramembranous ossification

57
Q

What is the sphene-occipital synchondrosis

A

This is the joint between the sphenoid and occipital bone

There is endochondral ossification here because we require the base of the skull to elongate

BDS2 BAMS Oral Biology (10 decks)

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