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