bone & cartilage

Question 1

describe cortical (compact) bone

Answer 1

dense outer plate

80-85% of skeleton

Question 2

describe cancellous (spongy) bone

Answer 2

internal trabecular scaffolding

15-20% of skeleton

Question 3

describe alveolar bone

Answer 3

cortical bone has nutrient canals, containing b.v.

cortical bone lining tooth sockets is penetrated by bundles of collagen fibres of PDL

Question 4

what is the composition of bone?

Answer 4

60% inorganic -HA
25% organic
15% water

Question 5

what is the organic component made of?

Answer 5

collagen
glycoproteins
proteoglycans

Question 6

what are the 2 components of the extracellular matrix?

Answer 6

ground substance

fibres

Question 7

describe ground substance?

Answer 7

semi-fluid gel
long polysaccharide molecules
glyco-amino-glycans

Question 8

what are the 2 GAG’s?

Answer 8

hyaluronic acid

proteoglycans

Question 9

what fibres are in the ECM?

Answer 9

collagen
elastin
other non-collagenous proteins

Question 10

what is the function of fibres in ECM?

Answer 10

reinforce extracellular ground substance

Question 11

what are the 2 types of microscopic bone?

Answer 11

woven and lamellar

Question 12

describe woven bone

Answer 12

rapidly laid down
irregular deposition of collagen
present in fetus
fracture repair
contains many osteocytes

Question 13

describe lamellar bone

Answer 13

laid down more slowly
collagen fibres laid down in parallel
normal form in adults
contains fewer osteocytes

Question 14

what is the structure of compact bone?

Answer 14

laid down in concentric lamellae
form longitudinal columns
organised in haversian systems around central canal
lateral canals
canals contain b.v

Question 15

describe the structure of cancellous bone

Answer 15

network of thin traveculae
trabeculae consist of lamellae
osteocytes present
no obvious haversian systems
thin bone nutrients can diffuse
bone marrow present in spaced between trabeculae

Question 16

describe osteoblasts

Answer 16

lie on surface of bone
derived from mesenchymal stem cells
synthesise and secrete collagen fibres forming a matrix
matrix mineralised by ca salts

Question 17

describe osteocytes

Answer 17

osteoblasts that become trapped in mineralised bone
lie within spaces- lacunae
contact other osteocytes via cytoplasmic processes that run in canaliculi
osteocytes also appear to communicate with osteoblasts

Question 18

describe osteoclasts

Answer 18

large multinucleate cells derived from haemopoietic stem cells
related to macrophages
resorb bone
lie in concavities in bone

Question 19

describe bone remodelling (turnover)

Answer 19

removal and replacement of bone tissue without change in shape
resorption balanced by deposition
each year 2% cortical, 25% cancellous
controlled by osteoblasts

Question 20

how is bone remodelling regulated?

Answer 20

hormones
-PTH, calcitonin
paracrines

Question 21

what is the reversal line?

Answer 21

scalloped edge shows where bone resorption changes to bone deposition

Question 22

when do tooth movements occur?

Answer 22

during eruption
post-eruptive eg mesial drift
orthodontic forces

Question 23

what do tooth movements require?

Answer 23

remodelling of adjacent soft and hard tissues

Question 24

what is cartilage?

Answer 24

semi-rigid, unmineralised CT

Question 25

what is in the cartilage matrix?

Answer 25

ground substance | fibres

Question 26

describe hyaline cartilage

Answer 26

widespread | larynx, nasal septum, trachea, ends of ribs, articular surfaces, embryonic skeleton

Question 27

where is fibrocartilage found?

Answer 27

intervertebral discs | pubic symohysis

Question 28

where is elastic cartilage found?

Answer 28

external ear, epiglottis, eustacian tube

Question 29

what are cartilage cells formed by?

Answer 29

chondoblasts

Question 30

how are chondrocytes formed?

Answer 30

chondroblasts get trapped in the matrix and become chondrocytes

Question 31

describe chondrocytes

Answer 31

avascular nutrient diffuses in some channels are present in thick areas of cartilage contain stores of lipid and glycogen

Question 32

what are the 2 types of bone growth?

Answer 32

endochondral ossification | intramembranous ossificaiton

Question 33

describe endochondral ossification

Answer 33

long bones cartilage precursor cartilage proliferation cartilage replaced with bone

Question 34

describe intramembranous ossification

Answer 34

flat bones bone formed de novo in CT no cartilage precursor

Question 35

what kind of bone growth occurs in the skull?

Answer 35

intramembranous ossification

Question 36

is there cartilage in skull?

Answer 36

no

Question 37

what areas of bone is there no calcification?

Answer 37

epiphysial

Question 38

when does epiphysial ossification begin?

Answer 38

when bone reaches final size

Question 39

what is the spheno-occipital synchondrosis?

Answer 39

special bone with mix of intramembranous and endochondral ossification base of skull no flexibility

Question 40

what is achondroplasia?

Answer 40

limited growth on base of skull spenoid bone not growing properly maxilla & mandible normal

Question 41

what kind of bone growth is the condyl?

Answer 41

endochondral

Question 42

what allows epiphysial growth in the TMJ?

Answer 42

fibrocartilaginous zone

Question 43

how does the mandible structure change over time?

Answer 43

condyl over lifetime articular emenants flat in children alceolar if teeth removed