Appositional bone growth
2 influencing factors of appositional growth
hormones and mechanical stresses
Thyroid hormone
bone growth via stim of osteoblast metabolic rate
Parathyroid hormone
increases blood ca+ levels by promoting osteoclast to resorb bone
glucocorticoids
increases bone loss impaired bone growth in children with chronic high levels of glucocorticoids
serotonin
inhibits osteoprogentitors cells into osteoblast at chronic high levels
mechanical stresses
muscle contractions and gravity force
mechanical stress
occurs during weight-bearing movement and exercise stressed osteocytes communicate to osteoblasts to synthesis more osteoid bone strengthens over period in response to stress
Bone Remodeling
ongoing process on peristeal/endosteal surface depend on osteoblasts, osteocytes and osteoclasts coordination
appositional growth
osteoblasts of inner layer of periostum produce/ deposit bone matrix increase in number/structure diameter of lamellae medullary cavity widens creating larger periphery constant
Calcitonin
promotes ca+ deposition in bone inhibits osteoclast activity
Sex hormone
stim osteoblasts promotes growth/closure of epiphyseal plate
growth hormone
stims liver production of IGF hormone causes bone elongation via proliferation of cartilage at epiphyseal plate