Exam 3 Study Guide Bone Vit D Ca Mg Phos BONE living tissue A Formation I Definitions Absorption Resorption Reabsorption the kidneys 1 Cortical bone dense and compact with a hard outer shell 2 Trabecular bone soft and spongy more metabolically active bone that is more able to donate calcium Has a higher turnover rate Hips and vertebrae Available for resorption when absorbing nutrients from the lumen of the intestine into your enterocyte breaking down something to pull the nutrients out of it already been absorbed once and reabsorbing it out of the blood or urine and into B 3 main types of bone cells 1 Osteoblasts bring on the bone bone building Originate in bone marrow Controlled by PTH and calcitriol which can up regulate or down regulate these osteoblasts Secrete collagen bone matrix osteoid Become embedded in the matrix and become osteocytes 2 Osteocytes carnivores that chew off the bone maintain integrity of surrounding bone During mineralization ca phosphorous and mg enter the bone fluid from blood and attach to bone proteins and ground substances Calcium salts make hydroxyapatite a Hydroxyapatite is a crystal lattice found in bones and teeth made of calcium salts aid on top of matrix With osteoporosis there are a lot of osteocytes but we don t have enough nutrients to build bone so we end up with weak bones 3 Osteoclasts buried alive embedded within the bone Large and multinucleated cells containing lysosomes that release acids proteases etc that break down the bone Respond to PTH calcitriol and calcitonin Help maintain blood calcium C Proteins in the bone 1 collagen 2 Osteonectin binds both calcium and collagen 3 Osteopontin binds hydroxyapatite and bone cells D Other bone cells 1 Fibroblasts Form collagen a long rod shaped protein that gives strength requiring iron vitamin C and vitamin D Involved in healing not just growth Form ground substances for bone tendons and ligaments 2 Chondrocytes 3 Reticulocytes Where we make RBCs or leukocytes E Bone remodeling 1 Bones are consistently remodeled throughout life Growth and maintenance Fracture repair Maintain serum calcium levels saving account for calcium 2 Bone mass Peaks in early adulthood Adolescents have the greatest activity and best time to add density Less long bone growth so you have the ability to add more bone Postmenopausal loss of estrogen leads to a large loss of bone mass Recommendation is that hormone replacement therapy is okay short term but should not be used over long term DEXA dual x ray absorptiometry is a great way to measure bone mineral density a Also measures lean vs fat mass Factors affecting bone mass a Protein is good for bones So those who exercise intake increased intake is associated with increased does cause loss of bone density intake does cause loss of bone density calcium excretion Even though calcium is being lost in the urine it is not related to osteoporosis b Caffeine Sodium c d Mechanical loading have higher bone mineral density e Smoking f Alcohol density g Calcium h Vitamin D Phosphorous i seems to come with loss of bone mineral density j Weight loss decreases absorption heavy alcohol use is tied to a decrease in bone mineral may play an even stronger role than calcium intake The Key Players Calcium Vitamin D Phosphorous Magnesium II DRI s want to know calcium and vitamin D values A Vitamin D RDA has been almost double over the past years Calcium mg d Vitamin D ug d Males 19 30 1000 15 Females 19 30 1000 15 9 18 1300 15 70 1200 20 III Sources of Vitamins and Minerals for bone A Calcium 1 Dairy milk cheese yogurt 2 Vegetables turnip or mustard greens broccoli cauliflower legumes tofu not spinach rhubarb or swiss chard 3 Seafood salmon sardines with bones clams and oysters 4 Fortified foods orange juice Average adult absorb about 30 of the calcium they consume but children can absorb up to 75 5 Supplements Calcium citrate malate Calcium monophosphate Calcium carbonate higher amount of absorption Avoid calcium carbonate from natural sources like oyster shell or dolomite due to aluminum and lead contamination And bone meal preparations can contain lead because they are naturally occurring not appropriate source for vegetarian or vegan B Phosphorous 1 Animal products organic phosphorous Meat poultry fish Milk and egg 2 Plant products inorganic phosphorous Legumes cereals whole grains Often in the form phytic acid or phytate 3 Other coffee tea soft drinks have phosphorous acid but too much can be a problem C Magnesium 1 Coffee tea cocoa 2 Whole grains legumes 3 Nuts 4 Leafy green vegetables chlorophyll 5 Hard water tap water D Vitamin D 1 Animal sources Beef Eggs Milk and dairy added to it not naturally there Saltwater fish salmon tuna 2 Fortified breads cereals 3 Plants almost none from plant products 4 Sunlight 10 minutes in the sun 10 g IV Vitamin D A Vitamin forms 1 Ergocalciferol D2 from plants sold commercially 2 Cholecalciferol D3 from cholesterol found in animal products B Metabolites 1 Plant sterol irradiated Vitamin D2 Ergosterol or pre vitamin D2 Ergocalciferol D2 or 1 25 OH 2D2 2 Cholesterol UV light Vitamin D3 Cholecalciferol or 25 OH D3 C Conversions of Vit D UV light hits our skin which can then turn into Cholecalciferol to liver calcidiol to kidney calcitriol 1 Liver 2 Kidney Cholecalciferol calcidiol Calcidiol 1 hydroxylase calcitriol o 1 hydroxylase activity is increased by low plasma calcium and PTH Activity decreased by high calcitriol concentrations and dietary phosphorous Purpose of Vitamin D is to maintain calcium levels Calcidiol is typically the form that you find in your bloodstream Calcitriol is the active form that acts on the tissues to maintain calcium levels In the small intestine Bile salts form around Vitamin D and fats forming a micelle Vitamin D can passively diffuse into the enterocyte with fats because it is a fat soluble vitamin The chylomicron circulates and drops of triglycerides at tissues The chylomicron remnants end up at the liver and enter via endocytosis At skin cells sunlight hits the skin turning cholesterol into Vitamin D3 natural sources always form the D3 form and only UVB rays do this conversion We have a Vitamin D Binding Protein DBP that binds D3 and transports it to the liver In the liver we convert D3 to calcidiol via 25 hydroxylase Calcidiol travels to kidney attached to another DBP In the kidney calcidiol is converted to calcitriol via 1 hydroxylase Kidney to Tissues Calcitriol attaches to a DBP and enters tissues via a Vitamin D
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