Bone composition and structure Flashcards
what is the mechanical purpose of bone
- protect organs
- provides body with shape
- facilitates mvmt
- provides framework for support
what is the axial skeleton + function
rib cage, spine, skull
- responsible for protecting internal organs
what is the appendicular skeleton + function
long and short bones
- supports locomotion and object manipulaton
where is marrow found
non mineralised tissue
- in almost all bones (not inner ear)
what is the function of marrow
generates the principal cells found in blood
hihgly osteogenic - can stimulate bone formation at extraskeletal regions
what is heterotopic ossification
when bone tissue is formed outside of the bone - progresses over time
- occurs following physcial trauma, some neurological trauma/spinal cord injuries
what are other names for trabecular bone
cancellous
spongy
where is trabecular bone found
cubodial, flat, and ends (epiphysis) of long bones
what is the porosity of trabecular bone
75-95%
what is formed in the bome matrix of trabecular bone
trabeculae - plates and rods (~200um thick)
- often randomly arranged
what is the role of trabecular bone
load distribution and load transfer in joints
what is another name for cortical bone
compact bone
where is cortical bone found
shafts of long bones and shells around vertebral bodies and other spongy bone
what is the porosity of cortical bone
5-10%
what is an osteon
cylindrical vascular tunnels formed in bone
what are haversian canals
canal in the middle of an osteon
- aligned longitudinally
- contain capillaries and nerves
what are vokmanns canals
short tranverse aligned canals that connect haversian canals
- contain blood vessels and nerves
how much cardiac output does bone receive
5-10%
explain lamellar bone
slowly formed
highly organised
parallel layers of anisotropic matrix of mineral crystals and collagen fibres
explain woven bone
quickly formed
poorly organised
randomly arranged mineral and collagen fibres
can lamellar or woven boen be remodelled into the other
woven can be remodelled into lamellar bone
is lamellar or woven bone stronger
lamellar is stronger
why is woven bone useful after an injury
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)
what is primary bone
tissue laid down on existing surface
what is secondary bone
bone resulting from remodelling
what type of bone is trabecular
all secondary (due to high turnover rate)
what type of bone are cortical osteons
secondary bone
is most adult bone primary or secondary
secondary
what is the function of collagen in bone
elastic and tough
what is the function of minerals in bone
gives bone its stiffness and strength
- minerals embedded in collagen
what is the composition of bone
25% water = mostly bonded to collagen
32% organic matrix = mostly collagen
43% apatite material
what is the orientation of collagen in bone
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
what is included in the total bone volume
hard bony matrix
voids with soft tissue
what is the bone volume fraction
Bv = bony matrix / total bone volume
Bv = Vm/Vt
what is the formula for porosity
pv = volume of soft tissue / total bone volume
pv = Vv/Vt
what does the bone volume fraction plus porosity equal?
1
(Bv + pv = 1)
what does porosity equal in trabecular and cortical bone
trabecular pv > 0.5
cortical pv < 0.5
what is the bone apparent density
mass of a volume of bone divided by its volume
what is the bone ash fraction
degree of mineralisation of bone tissue
- independent of porosity
what does bone ash fraction measure
ratio of amount of mineral to amount of collagen
does bone ash fraction vary in healthy people
no
- only varies in people with genetic bone conditions
