Bone Formation and Remodeling Flashcards
Osteogenesis types
Intramembranous - where it forms in embryo
Endochondral - where is forms from previous formed hyaline cartilage template of future bone
intramembranous ossification
Mesenchymal cells condence into a membrane and have increased vascularization
Osteoblasts idfferentiate and secrete osteoid to form templates
Calcium phosphate salts depositied in the matrix and osteocytes formed
Endochondral ossification
Development and growth of long bones
Cartilaginous template
Endochondral steps
Hyaline cartilage is template of a long bone
Osteoprogenitor cells of the perichondrium form the periosteal collar (becomes mineralized)…this cuts the middle off and becomes primary center of ossification
BV of periosteal bud enter through periosteal collar
BV delivers the monocytes that become osteoclasts
Osteoblastsd will deposit osteoid on the surface of the spicules
Other ossification
Secondary ossification occurs at one of the epiphyses
Space between primary and secondary is epiphyseal growth plate
Eventually becomes a line
When does bone growht cease
When cartilage production within plate is overcome by mineralization and erosion by osteoclasts
Regions of long bone
Epiphysis, metaphysis, diaphsis
Periosteum on the outside
Endosteum (stroma)
Metaphyseal region zones
Reserve - furthest from oss center and no growth
Prolif - chrondrocytes proliferates cause active growth toward quiescent zone
Hypertrophic zone - when cells division stops and laceunae enlarge and grwoth in length…facilitate calcification
Calcification zone- chrondrocytes enlarged and matrix becomes calcified
Ossification zone - chrondrocytes degerneative due to lack of oxygen…matrix dissolves nad walls digested by osteoclasts ….osteoblasts secrete osteoid to form spongy trabeculae and osteoclasts resorb to enlarge the cavity
Bone growht in width
Intramembranous in nature
Occurs under the periosteum
How does spongy become compact bone
Spongy bone primordium
Becomes filled by osteoid from osteoblasts to form a primary osteon…also bring monocytes that will fuse to become osteoclasts
Oston constructuon
Created in empty spaces
Spaces sequantially narrowed by addition of teon construction
BV always in the middle lined by BLCs
Osteoclastic osteolysis
Involves osteoclasts
Long-term mainntennance
Osteocytic osteolysis
Short term adjustments
Dissolution of hydroxyapatite rystals with minimals degradation of collagen or ground substance
Walls of the lacunae are degraded
Spongy bone remodeling structuee
Reversal line - where bone resorption ceased and new osteoid deposits began
Trabecular packets present
Bone remodeling
Typical bone lined by BLCs, lamina lamitans, and unmineralized osteoid layer
SIgnals from BLCs will destory the osteoid so that osteoclasts can get ot bone and begin osteolysis
