bone structure and function Flashcards
what is bone composed of
living cells in mineralised extracellular matrix
what is hydroxyapatite
hydrated crystalline material of calcium and phosphate
bone matrix
collagen I and V
crystals of carbonated hydroxyapatite
bone function
support
protect
movement
metabolic function of bone
haematopoiesis (production of new blood cells)
calcium homeostasis
bone types
cortical outer, strong trabecular inner, spongy meshwork woven first bone formed, remodelled
what is found on the outside of cortical bone
periosteum
contains collagen, fibroblasts, stemcells
what covers the outside of trabular bone
endosteum
describe trabecular
contins matrix
ostocytes in matrix
osteoblasts on edges
describe woven bone
unorganised
cellular
becomes mineralised
cell types in bone
osteoclast osteoblast osteocyte pre-osteoblast? bone lining cells osteoprogenitor cells
phases of remodelling
resorption phase bone ECM destroyed 3 weeks bone formation new ECM formed/mineralised 3-4 months
what is important for maintenance and formation
mechanical forces
systemic factors stimulating bone resorption
parathyroid hormone - stimulate osteoblasts to produce Oc stim factors
1-25, dihydroxy vit D3
thyroid hormone
systemic factors promoting bone formation
parathyroid
1-25 dihydroxy vit D3
local factors that stimulate bone resorption
inflammation
tumour necrosis factors
local factors promoting bone formation
bone morphogenic protiens
bone diseases
osteoporosis - loss of oestrogen periodontitis pagets disease - bone not fully mineralised rheumatoid arthritis
bone remodelling process
sclerotin prevents osteoblasts forming new bone
micro fracture sets off one remodelling, osteocytes SOS factor
activate storm cells - producing MCSF
stimulates osteoclast precursors
precursors carry RNAK on surface
stroll cells produced daughter cells with RNAK L
RANK L activates RANK
preosteoclasts fuse and form multinucleate osteocloasts
bone linig cells allow osteoclasts to adhere - release HCL to dissolve mineral and cathepsin K to chew ECM forming Howships lacuna
osteoclasts die by apoptosis, GF released
daughter cells produce OPG (sits over RANK)
osteoblasts create matrix ,mineralised
some osteoblasts lett to form osteocytes
what does sclerostin do
prevents Ob making bone
function of osteocyte s
sense what is happening in bone
secrete schlrostin
