Bone composition and structure

Question 1

what is the mechanical purpose of bone

Answer 1

• protect organs
• provides body with shape
• facilitates mvmt
• provides framework for support

Question 2

what is the axial skeleton + function

Answer 2

rib cage, spine, skull
- responsible for protecting internal organs

Question 3

what is the appendicular skeleton + function

Answer 3

long and short bones
- supports locomotion and object manipulaton

Question 4

where is marrow found

Answer 4

non mineralised tissue
- in almost all bones (not inner ear)

Question 5

what is the function of marrow

Answer 5

generates the principal cells found in blood
hihgly osteogenic - can stimulate bone formation at extraskeletal regions

Question 6

what is heterotopic ossification

Answer 6

when bone tissue is formed outside of the bone - progresses over time
- occurs following physcial trauma, some neurological trauma/spinal cord injuries

Question 7

what are other names for trabecular bone

Answer 7

cancellous
spongy

Question 8

where is trabecular bone found

Answer 8

cubodial, flat, and ends (epiphysis) of long bones

Question 9

what is the porosity of trabecular bone

Answer 9

75-95%

Question 10

what is formed in the bome matrix of trabecular bone

Answer 10

trabeculae - plates and rods (~200um thick)
- often randomly arranged

Question 11

what is the role of trabecular bone

Answer 11

load distribution and load transfer in joints

Question 12

what is another name for cortical bone

Answer 12

compact bone

Question 13

where is cortical bone found

Answer 13

shafts of long bones and shells around vertebral bodies and other spongy bone

Question 14

what is the porosity of cortical bone

Answer 14

5-10%

Question 15

what is an osteon

Answer 15

cylindrical vascular tunnels formed in bone

Question 16

what are haversian canals

Answer 16

canal in the middle of an osteon
- aligned longitudinally
- contain capillaries and nerves

Question 17

what are vokmanns canals

Answer 17

short tranverse aligned canals that connect haversian canals
- contain blood vessels and nerves

Question 18

how much cardiac output does bone receive

Answer 18

5-10%

Question 19

explain lamellar bone

Answer 19

slowly formed
highly organised
parallel layers of anisotropic matrix of mineral crystals and collagen fibres

Question 20

explain woven bone

Answer 20

quickly formed
poorly organised
randomly arranged mineral and collagen fibres

Question 21

can lamellar or woven boen be remodelled into the other

Answer 21

woven can be remodelled into lamellar bone

Question 22

is lamellar or woven bone stronger

Answer 22

lamellar is stronger

Question 23

why is woven bone useful after an injury

Answer 23

used to strengthen quickly after an injury because it can be laid down fast
- found at sites of fracture healing, tendon and ligament attachments (sites of rapid turnover)

Question 24

what is primary bone

Answer 24

tissue laid down on existing surface

Question 25

what is secondary bone

Answer 25

bone resulting from remodelling

Question 26

what type of bone is trabecular

Answer 26

all secondary (due to high turnover rate)

Question 27

what type of bone are cortical osteons

Answer 27

secondary bone

Question 28

is most adult bone primary or secondary

Answer 28

secondary

Question 29

what is the function of collagen in bone

Answer 29

elastic and tough

Question 30

what is the function of minerals in bone

Answer 30

gives bone its stiffness and strength - minerals embedded in collagen

Question 31

what is the composition of bone

Answer 31

25% water = mostly bonded to collagen 32% organic matrix = mostly collagen 43% apatite material

Question 32

what is the orientation of collagen in bone

Answer 32

in primary bone - long fibres, oriented along the direction of the structure in osteonal bone - forms concentric rings inside osteons - mineral forms along the collagen

Question 33

what is included in the total bone volume

Answer 33

hard bony matrix voids with soft tissue

Question 34

what is the bone volume fraction

Answer 34

Bv = bony matrix / total bone volume Bv = Vm/Vt

Question 35

what is the formula for porosity

Answer 35

pv = volume of soft tissue / total bone volume pv = Vv/Vt

Question 36

what does the bone volume fraction plus porosity equal?

Answer 36

1 (Bv + pv = 1)

Question 37

what does porosity equal in trabecular and cortical bone

Answer 37

trabecular pv > 0.5 cortical pv < 0.5

Question 38

what is the bone apparent density

Answer 38

mass of a volume of bone divided by its volume

Question 39

what is the bone ash fraction

Answer 39

degree of mineralisation of bone tissue - independent of porosity

Question 40

what does bone ash fraction measure

Answer 40

ratio of amount of mineral to amount of collagen

Question 41

does bone ash fraction vary in healthy people

Answer 41

no - only varies in people with genetic bone conditions