Reserve Cartilage
-anchors growth plate to bone
-precurser for other zones
Cell proliferation
-rapid cell division
-flattened lacunae
Cell hypertrophy
cells enlarge & remain in columns? develops framework for bone to be laid down
calcification
osteoblasts lay down collagen fibers/secrete minerals between columns
Bone Deposition
lacunae break down and chondrocytes die
endochondral bone growth
bone growth occurs from inward and expands outward
Pathologies
achondroplastic dwarfism and giantism
Describe the difference in bone structure between an athlete and someone who spends a significant amount of time sitting. Would the bones look identical? Why or why not?
Architecture of bone determined by mechanical stress
-Form of bone shaped by experience
-Athlete: more active osteoblasts; stronger bones
-Couch potato: more active osteoclasts; weaker bones
Bone Deposition process
-building up bone (osteoblasts)
-Osteoblasts lay down collagen fibers
-Minerals harden matrix (Ca2+, P, & others)
-Hydroxyapatite crystallizes to solubility product
-Ca2+ + PO4- reach critical value
Bone Reabsorption Process
-breaking down bone (osteoclasts)
-H+ secreted by into tissue fluid
-Followed by Cl- ions
HCL ph 4 dissolves bone
-Cathepsin K digests collagen
osteoporosis
osteoclasts>osteoblasts