12 - Nutri Sci 11/12 2008-11-12 Bone processing:...

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Nutri Sci 11/12 15:58 Bone processing: Remoldeling Remodeling Allows bone to reshape itself Adapt to stresses Allows injury to heal  Allows bone to be a calcium reservoir Calcium Hydroxyapatite Muscle contraction Blood clotting Enzymes Cell signaling Low intake   low blood Ca Parathyroid hormone released Acts on kidney to increase activation of vitamin D precursor.  D acts on mucosal cells to increase absorption of Ca Efficiency o Increase calcium diet, < ¼ Ca absorbed o Decrease calcium diet, ½ Ca absorbed
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Fallback: PTH also stimulates osteoclasts Dissolve bone and matrix Release Ca  increase blood Ca PHT increases absorption and resorption absorption of Ca from diet resorption of Ca from diet net effect is to increase blood Ca High intake   high blood Ca thyroid rleaseds calcitonin stimulates osteoblasts form new bone take up calcium from blood BOTTOM LINE: Blood Ca maintained at any cost to bone When Ca intakes increase, form new bone When calcium intakes are decreased, dissolve bone and release Ca Bone Ca is more important than blood Ca Factors affecting calcium status Negative Ca balance Urinary or fecal loss
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o Diuretics Caffeine Alcohol High protein (kidney stones) o Fecal losses Phosphorous makes insoluble compound
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This note was uploaded on 04/07/2009 for the course BIO 10167 taught by Professor Anderson,peterj. during the Fall '08 term at Wisconsin.

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12 - Nutri Sci 11/12 2008-11-12 Bone processing:...

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