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Intro to Bones.docx

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NUTR 1010
Anneke Olthof

Intro to Bones  Bones are dynamic, living organs!  Have many important roles in the body  Bone diseases can be life-threatening and debilitating Functions of Bones  Structural support  Protection of vital organs  Attachment point -for muscles and ligaments  Nutrient reservoir -calcium, phosphorus  Production of blood cells - in the bone marrow What are bones made of?  Appx 70% mineral -Hydroxyapatite - calcium and phosphorus crystals -provides strength and rigidity  The other 30% …. -collagen matrix (proteins) - provides flexibility and durability -blood vessels, nerves, cartilage connective tissue Nutrient involved in Bone Health  Major roles: - Calcium - Vitamin D - Phosphorus  Minor roles: - Vitamin K - Vitamin A - Protein - Fluoride - Magnesium Processes of Bone Development  Bone Growth -begins in the womb  Bone modeling -longitudinal growth -steady change in size and shape of bones - stops after puberty  Bone remodeling (aka bone turnover) - minimal changes in size and shape - continues throughout lifetime -involves bone resorption and bone formation Balance of Bone Remodeling  Bone Resorption - osteoclast break down bone - secrete enzymes to digest bone mineral - minerals are released to the bloodstream  Bone Formation - Osteoblasts build new bone -build collagen matrix -hydroxyapatite mineralizes around collagen Skeletal Maturity vs. Peak Bone Mass  Skeletal Maturity - bones reach final size (length) and shape - End of puberty  Peak Bone Mass - bones reach final diameter and density - influenced by diet and exercise -appx 30 years of age? Bone Mineral Density (g/cm2)  Bone mineral content (in grams) measured in a certain Area (cm2) of bone  Represents bone strength and fracture risk  Less bone mineral = more fracture risk  Decreases with age - After bone mass is achieved  Usually measured using DXA  Dual energy x-ray absorptiometry  Measures bone mineral density  Used to: - monitor change in bone density -diagnose osteoporosis (chart on course link) T-Score  compares your bone density to average peak bone density of a 30 yr. old healthy adult low bone mass ( less than minus one to minus 2.5)  osteopenia (reversible) Osteoporosis  A skeletal disease characterized by: - low bone density -increase bone fragility - increase fracture risk  Literally means “porous bones”  Asymptomatic until fracture occurs  Most prevalent bone disease in North America Age Influences Osteoporosis Risk  Risk increases with older age - bone density decreases gradually with age - bone layers rebuild on surface - minerals released from inner bone matrix - bone become wider and less dense  Longer life expectancies = increase osteoporosis Gender Influences on Osteoporosis Risk  Women 3 x higher risk than men - lower peak bone mass - longer life expectancy -Estrogen not produced post-menopause  Estrogen decreases bone resorption and increases bone formation  Without estrogen bone remodeling balance is uneven, start to decrease our bone density (graph on course link) Non-modifiable Risk Factors for Osteoporosis  Age  Gender - female higher risk  Ethnicity – Asian and Caucasian populations are higher
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