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Collagen fibers randomly oriented. Formed during fetal development and during fracture repair. for fractures it is laid down to stop blood loss.
Mature bone insheets called lamellae. Fibers oriented in one direction in each layer, but in different directions in different layers for strength. Extremely strong:resistant to bending, twisting, compacting. Osteocytes (w/lacunae) arranged in layers sandwiched between lamellae.
How Bone is Classified?
Whether woven or lamellar, can be classified according to amount of bone matrix relative to amount of space w/in bone. Spongy bone has less matrix and more space than compact bone.
Interconnecting rods or plates of bone. Like scaffolding. spaces flled w/red & yellow marrow & blood vessels, covered w/endosteum, lines the inner cavities of bones, oriented along stress lines, will reorient if stress changes. Osteoporosis - trabeculae breaks down and more prone to fracture.
denser and has fewer spaces than spongy bone; consist of Central (Haversian) canals, Lamellae, Osteon (Haversian) System, Perforating (Volkmann's) canal
Central (Haversian) Canals
in compact bone - run parallel to long axis and lined w/endosteium and contain blood vessels, nerves and loose connective tissue
in compact bone - concentric, circumferential, interstitial - primarily oriented around blood vessels that enter substance of bone itself
forms outer surface of compact bone - thin plates that extend around bone.
between osteons. Remnants of concentric or circumferential lamellae (osteons) there were partially removed during bone remodeling
Osteon (Haversian) System
in compact bone - consists of single central canal, its contents, associated concentric lamellae and osteocytes. Blood vessel-filled central canal (Haversian canal), Lacunae and canaliculi contain osteocytes and fluid.
What does osteon (haversian) system look like?
Cross section - resembles circular target; 'bulls-eye' is central canal and 40-20 concentric lamellae form rings. Osteocytes located in lacunae etween lamellar rings, and caniliculi radiate between lacunae across lamellae, looking like minute cracks across rings of target.
Perforating (Volkmann's) Canal
in compact bone - perpendicular to long axis and not surrounded by concentric lamellae but pass through it. Both perforating and central canals contain blood vessels. Direct flow of nutrients and waist to and from osteocytes via: interstitial fluid of lacunae and caniculi and from osteocyte to osteocyte by gap junction.
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