MSK Exam 1 Flashcards
(206 cards)
yellow marrow is where
medullary cavity of diaphysis of long bones
red marrow is where
spaces in epiphyses and other spongey bone
hematopoiesis
organic bone matrix
1/3 bone weight
type I collagen
tensile strength
also osteonectin, ossteopontin, proteoglycans, gammacarboxyglutamic acid
inorganic mineral salts
2/3 bone weight
mainly calcium phosphate as crystals called hydroxyapatite
gives hardness and compressional strength
also amorphous calcium phosphates
pyrophosphate does whate
prevent calcium phosphate crystalization in extracellular tissues
osteopbalsts
bone forming cell
produce collagen 1, osteocalcin, osteopontin
-tissue nonspecific alkaline phosphatase on surface breaks pyrophosphate so calcification can occur
-produces nucleotide pyrophosphatase phosphodiesterase 1 (NPP1) and ankylosis protein (ANK) to make pyrophosphate available
-PTH and vit D receptors to regulate RANKL, OPG, MCSF1
osteocyte
remain in cortical bone during remodeling
-permits translocation mineral in and out of remodeling regions
-mechanical sensors provide signals for remodeling
-produce factors modulating distant tissue function (FGF23 affects phosphate excretion and vit d metabolism)
osteoclast
multinucleated giant cells for bone resorption
after sealing area develop invaginated structures culled ruffled border which acts as lysosome (secretes acid and proteases like cathepsin K)
-controlled by number of osteoclasts (macrophage colony stimulating factor 1) and osteoclast activity (PTH, vit d through induction of RANKL)
endochondral ossification
at epiphyseal plate
cartilage mold develops
cartilage converted to bone (as plate widens part next to diaphysis becomes bone)
epiphyseal plate ossifies near end of puberty to end growth
formation of bone
osteoblast secretes collagen and ground substance
colagen forms osteoid and entraps osteoblasts to form osteocytes
calcium salts precipitate and form hydroxyapatite crystallization
importance of bone remodeling
-old bone becomes brittle and weak
-adjust strength in proportion to bone stress
-adjust for mechanical forces in accordance with stress patterns
bone remodeling
complete cycle may take 6 months
-physical or biochemical signals precursor osteoclasts from bone marrow to specific loci on bone
-form osteoclasts which cut tunel through bone
-osteoblasts reverse tunnels to new bone
remodeling trabecular bone
osteoclast digs cavity
osteoblasts recruited to base
calcification occurs
bone returns to quiescent state
hormonal control bone resorption
-PTH binds osteoblasts which secrete RANKL and MCSF1 (bind preosteoclasts), preosteoclasts form into osteoclasts and activity stimulated by RANKL, osteoclasts for ruffled border and release enzymes and acids
-osteoblasts secrete osteoprotegrin (OPG) which is decoy for RANKL, low OPG/RANKL ratio increases osteoclast formation and activity
-RANKL stimulated by vit d, pth, pthrp, il11, il6, il1, glucocorticoids
-estrodiol promotes OPG
factors for bone deposition
compression load - greater compression greater bone deposition
bone shape - altered with increased deposition
rate of fracture repair - depends whether use maintained or immobilized, fracture plates
dietary availability calcium
increased osteoclast activity in
hyperparathyroidism
hyperthyroidism
hypervitaminosis D
hypogonadism (postmenopause)
pagets disease
-increased osteoclast activity causes -increased osteoblast activity
-irregular bone formation - disorganized
-increased density in some areas but still weak
growth hormones
increase bone remodeling
stimulate cartilage growth
sex steroids
testosterone and estradiol promote osteoblast activity
glucocorticoids
increase RANKL, inhibit OPG, increase osteoclasts
deplete osteoblasts by inhibiting replication precursors
suppress gonadotropin causing hypogonadal state
increased renal calcium loss and intestinal calcium loss cause increased PTH
estrogen
activates osteoblasts and secretion of OPG
decrease in postmenopause causes bone resorption to be greater then deposition so lose bone mass
Salter Harris classification
1 - S: separation through physis (degenerating cartilage cells)
2 - A: above physis
3 - L: lower than physis
4 - TE: through everything
5 - R: cRushed physis
anterior shoulder dislocation
axillary nerve injury
closed reduction, immobilization, PT
posterior shoulder dislocation
seizures and electrocutions