Backbone part 3
Terms in this set (16)
appositional growth
growth of all bones in width
what happens in appositional growth
osteoblasts between periosteum and bone surface lay down new bone
oppositional growth beginning
formation of new circumfrential lamellae, deeper circumferential lamellae are removed or added to osteons
appositional growth end
primarily thickens compact bone of diaphysis , osteoclasts in medullary cavity digest innner circumferential lamellae so medullary cavities enlarge as well
growth hormone
produced by anterior pituitary gland, highest amounts during childhood
growth hormones function in bone
increase mitosis of chondrocytes promoting longitudinal growth, more activity of osteogenic cells, stimulate osteoblasts in periosteum triggering appositional growth
testosterone
male, thicker bones, gretaer clacium deposits, growth spurts , accelerate closure of epiphyseal plate
estrogen
female, similar affects as testosterone , epiphyseal plate closed at 14-15
gigantism
excess growth hormone secreted before closure of epiphyseal plates
acromegaly
excess growth hormone secreted after closure of epiphyseal plates, enlarged bones of skull, face, hands, heart and kidney malfunction
bone remodeling
continual process of bone formation by bone deposition, bone loss by bone resorption
reasons for bone remodeling
maintenance of calcium homeostasis, repair, replacement of primary bone, replacement of old bone, adaptation to stresses
healthy bone
formation and loss happens simultaneously
bone deposition cells
osteoblasts in periosteum and endosteum
what do osteoblasts do in deposition
secrete proteoglycan and glycoproteins that bind to calcium ions and secrete vesicles containing calcium ions, ATP and enzymes
what do vesicles do
bind to collagen fibers, calcium ions crystallize, vesicles rupture , begins process of calcification