metabolic bone disorders - histopathology Flashcards
what are the functions of bone
structure - give structure and shape to the body
mechanical - sites for muscle attachment, allow movement of the structure
protective - vital organs and bone marrow, eg skull and ribs. by protecting marrow bones support preoduction of blood and stroma cells
metabolic - reserve of ca and other minerals
what is the composition of bone *
inorganic - 65%
- ca hydroxyapatite
- is a storehouse for 99% of ca in body, 85% phosporus, 65% Na and mg
- release these minerals to systems that need them
organic - 35%
- bone cells and protein matrix (ECM proteins, collagen fibres and linking proteins needed to form, shape and repair the bone)
what are the features of typical bones
have condyles which are on articular surfaces and synovial joints
pully shaped region - trochlea
fovea - small dip/depression on bone eg on femoral head - where it is a ligament attachment
underneath the articular surface have the subchondral bone - provide support for the cartilage
epiphysis line - separates the epiphysis from the bulk of the bone
main bulk is in the diaphysis
medulla is surrounded by the cortex that is surrounded by the periosteum
metaphysis - join the epiphysis to teh diaphysis - during growth this contains the cartilaginous growth plate - allows linear growth of bones. area where trabecular bone is found - provides strength and involved in turnover of minerals
what can be seen on the x-ray *
poorly circumscribed lytic lesion - in diaphysis of bone that has eroded the cortex - see no bone here
periosteal reaction - new bone outside of the normal bone
what can be seen on the x-rau *
well circumscribed lytic lesion in metaphysis of tibia that has broken through the cortex
what are the types of anatomical bone
flat - eg skull/rib, protective
long - eg femer/tibia, for weight support, linear growth and movement
short/cuboidal - eg carpal/tarsal, stabalise and fascilitate movement
irregular - vertebrae/pelvis, protect specific organs
sesamoid - in tendons
what are the classifications for macroscopic structure of bone *
trabecular/cancellous/spongy - criss cross through medullary cavity
cortical/compact
what are the classifications for microscopic bone structure *
woven bone - immature
lamellar bone - mature
describe cortical bone *
make up the outside of the shaft
is the bulk of the long bones and appendicular skeleton
makes up 80% of the skeleton
80-90% calcified
has a low turnover
mainly structural, mechanical and protective
describe trabecular bone *
make up bulk of vertebrae and pelvis and axial skeleton
15-25% calcified - low mineralisation
20% of skeleton
metabolic function - high turnover - large SA fasciliates this
describe cortical bone microanatomy *
made of parallel osteons (0.2mm diameter) that surround the conversion canal containing bv
osteons are circular structures of lamella bone
in periosteum get circumfrential lamellae that go all around all of bone
interstitial lamellae - are between the osteons
in trabeculae have lamellae but they are in layers not in osteons
osteocytes have dendritic Canalicular Networks throughout the lamellae structure
describe woven bone *
disorganised
it is found in the developing skeleton - initial bone that is layed down before it is replaced
when there is rapid growth or pathological high turnover
weak bone
what are the 3 types of bone cell *
osteoclasts
osteoblasts
osteocytes
describe osteocytes *
90% of bone cells
live 25yrs
form a mechanosensory network and tell other cells what to do
describe osteoclasts *
multinucleated
form haemopoetic lineage
the resorb/remove bone
describe osteoblasts *
mononuclear
produce osteoid to form new bone
describe the bone remodelling cycle
osteoblasts make RANKL and M-CSF which are the key osteoclastic factors that cause cells to differentiate into osteoclasts
blasts also make a decoy receptor for RANKL
blasts control amount of clasts that are forming
osteocytes sense damage/new stresses - signal for osteoclasts to come to site that needs to be remodelled/removed
osteocytes signal by apoptosing and so releaseing RANKL - signal for osteoclasts to form here
osteoclasts resorb away bone
osteoclasts die away as reversal phase occurs
osteoclasts are recruited to site and produce osteoid to replace lost bone
describe this image *
multinuclear cell resorbing bone
cuboidal cell on surface is an osteoblast
osteocyte is in the osteocytic lacunae
why perform a bone biopsy *
to confirm the diagnosis of a bone disorder
when you need histological evidence
to find the cause of or evaluate ongoping bone pain/tenderness - when bone marker/histological evidence has not been useful
investigate abnormality seen on x-ray
for bone tumour diagnosis - benign v malignant
to determine cause of unexplained infection
to evaluate therapy performance
risk of biopsy *
low risk
chance of infection/fracture - if can avoid them then you should
explain the 2 types of bone biopsy *
closed - core biopsy with jamshidi needle inserted into bone, returns with a core of bone
open - for sclerotic/inaccessible bone - scleroti means it ahs thickened so cant get in. Or if you need a large sample. There is more risk
why do you do a transiliac bone biopsy *
see all the types of bone here - cortical and trabecular in the core of bone
