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lecture 5 bone

Terms in this set (27)

function
protect
reservoir
locomotion
support
Composition
28% type I collagen
67% hydroxyapatite
5% other proteins
Outer Periosteum
"Fibrous layer"
Dense regular CT
Fibroblasts
Inner Periosteum
Very vascular
"Osteogenic layer" (layer of bone forming cells)
Progenitor bone cells (osteoblasts)
Three layers (lamella):
circumferential
concentric
interstitial
Circumferential
: encloses adult bone and forms interior and exterior boundaries
Concentric
bulk of compact bone. Contain osteons or haversian
Interstitial
space between osteons
Canaliculus
communication b/w osteocytes
Endosteum
Loose CT between interior circumferential lamella and trabecular bone
Less active osteogenic cells than periosteal cells
Trabecular bone (D)
"Cancellous, spongy bone"
CT, ECM
Marrow: contains adipocytes, hematopoietic stem cells and developing blood cells
Osteogenic
Osteoprogenitors
Preosteoblasts Osteoblasts
Ectomesenchymal origin in
head
Mesenchymal
everywhere
High levels of alkaline phosphatase activity on outer surface of cell membrane does what?
increases bone formation
Osteoblasts produce protein matrix of bone
Type I collagen
Proteoglycans
Other proteins
PTH and 1,25-dihydroxyvitamin D
Can cause bone resorption at high concentrations
Calcitonin
Estrogen
inhibits resorption
Leptin
Produced by adipocytes
Inhibits serotonin, causing bone resorption and appetite
Inhibits osteoclasts
Rapid bone formation leads to more trapped
osteocytes
Volkmanns' canals
nourish osteocytes cell processes
Osteoclasts come from where?
Hematopoietic in origin (coming from blood stem cells)
Intramembranous Bones
Skull bones, maxilla, body of mandible, and midsection of long bone
1. Intramembranous Bone Formation
Mesenchymal (undifferentiated fibroblasts) cells proliferate, congregate and differentiate into osteoblasts
Collagen fibrils accumulate extracellularly to start formation of osteoid layer
Newly formed osteoblasts begin to produce alkaline phosphatases which induces mineralization
Mineralization occurs, trapping osteocytes
"Islands" of bone spicules fuse to form a bony plate surrounded by mesenchyme (ECM/CT)
Mesenchyme becomes marrow space
Endochondral Ossification
Ends of all long bones, vertebrae, ribs and articular end of mandible
Endochondral Ossification formation
Mesenchymal cells congregate in the limb bud and differentiate into chondroblasts surrounded by perichondrium
Chondroblasts proliferate and become arranged in longitudinal columns
mineral deposition
vascularization occurs
Perichondrium converts to periosteum
Calcified cartilage disintegrates via chondroclasts
Mineralized bone + mineralized cartilage =
primary spongiosa
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