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BDS2 BAMS Oral Biology > Bone and Cartilage > Flashcards

Flashcards in Bone and Cartilage Deck (57)
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1

What are the 2 types of bone

cortical/compact
cancellous/spongy

2

describe cortical bone

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

3

describe cancellous bone

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

4

what are the 3 components to alveolar bone

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)

5

what does the cancellous bone contain

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

6

what does the cortical bone lining tooth sockets penetrated by

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

7

what is the composition of bone

60% inorganic
15% water
25% organic

8

what makes up the organic component

collagen (90%)
glycoprotiens
proteoglycans

9

what is the function of the proteoglycans

responsible for jelly structure of the matrix

10

what are the two different ways bone can be resorbed

horizontal
vertical

11

what is horizontal resorption

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

12

what is vertical resorption

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

13

what is the ECM made up of

ground substance and fibres

14

what is ground substance

semi fluid gel

15

what does ground substance contain

long polysaccharide molecules
glycosaminoglycans

16

what are the fibres found in the ECM

Collagen

Elastin

Other non-collagenous proteins

17

what are the two types of microscopic bone

woven
lamellar

18

describe woven bone

rapidly laid down
irregular deposition of collagen
contains many osteocytes

19

where is woven bone found

fetus
fracture repair

20

describe lamellar bone

Laid down more slowly so well organised

Collagen fibres laid down in parallel

Normal form in adult
contains fewer osteocytes

21

what is the structure of compact bone

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

22

what is the function of the interconnecting projections of the osteocytes

their function is nutrition but also communication

23

describe cancellous bone

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

describe osteoblasts

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

describe osteocytes

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

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

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

describe osteoclasts

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

what is bone remodelling controlled by

osteoblasts

29

what i the process of bone turnover regulate dby

hormones - PTH, calcitonin
paracrine - various cytokines

30

what happens in bone turnover

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)