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Published byTiffany Jocelin Pope Modified over 8 years ago
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Material Constituents: Calcium carbonate and Calcium phosphate 60-70% bone weight Adds stiffness Primary determinant for compressive strength. Collagen Adds flexibility Contributes to tensile strength
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Diaphysis: shaft Periosteum: fibrous connective tissue covering shaft Epiphyses: the ends Articular cartilage: hyaline cartilage covering epiphysis Epiphyseal line & plate: the growth plate or the line left over in adult bones Medullary Cavity: cavity in bone that contains marrow
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Haversian Canal: Central Canal surrounded by concentric layers of calcified matrix called lamellae. Osteocytes are found between concentric lamellae and connected to each other, and the central canal by canals called canaliculi. This network permits the exchange of nutrients and metabolic waste.
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Compact Bone Low porosity 5-30% bone volume is non-mineralized tissue Withstand greater stress but less strain before fracturing
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Spongy Bone High porosity 30 - >90% bone volume is non-mineralized tissue Trabeculae filled with marrow and fat Withstand more strain (but less stress) before fracturing
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The replacement of other tissues with bone
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Endochondral and Intramembranous
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Most Bones of the Skeleton Bone develops from cartilage Blood vessels infiltrate cartilage, forming bone Primary ossification begins at the center of the diaphysis Secondary centers form later at the epiphyses
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Skull, Mandible and Clavicle Bone develops directly not from cartilage Develops from the inside out from spongy to dense bone
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Epiphyseal and Appositional
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Virtually all growth in length occurs at the growth plates Growth plates fuse after puberty,as rate of ossification exceedes the growth of cartilage. Once the growth plate is entirely ossified (fused) there can be no further growth in bone length This limits the size of adults
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Growth in circumfrence The inner layer of the periosteum builds concentric layers of bone
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Osteoblasts build new bone Osteoclasts reabsorb bone
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Wolf’s Law Indicates that bone strength increases and decreases as the functional forces on the bone increase and decrease. Bone Modeling and Remodeling Mechanical loading causes strain Bone Modeling If Strain > modeling threshold, then bone modeling occurs.
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Bone mineral density generally parallels body weight Body weight provides most constant mechanical stress Determined by stresses that produce strain on skeleton Think: weight gain or loss and its effect on bone density
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An increase in bone mass due to predominance of osteoblast activity. Seen in response to regular physical activity Ex: tennis players have muscular and bone hypertrophy in playing arm. The greater the habitual load, the more mineralization of the bone. Also relates to amount of impact of activity/sport
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A decrease in bone mass resulting form a predominance of osteoclast activity Accomplished via remodeling Decreases in: Bone calcium Bone weight and strength Seen in bed-ridden patients, sedentary elderly, and astronauts
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Bone is an important living tissue that is continuously being remodeled. Bone Strength and Resistance to fracture depend on its material composition and organizational structure. Bones continually change in density.
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