calcium, phosphate, and vitamin D metabolism
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| calcium is important in ECF and ICF and is essential to normal function of many biochemical processes such as these: | neuro-muscular excitability, blood coagulation, hormonal secretion, enzymatic regulation
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| calcium salts in bone provide this | structural integrity of the skeleton
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| what percent of bone is calcium? | ninety
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| this part of bone is a frequent site of osteoporotic bone fracture and is extremely sensitive to calcium deficiency due to its relatively high rate of turnover. | trabecular bone
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| what are some symptoms of low calcium levels? | convulsions, arrythmias, tetany, numbness/parasthesias in hands, feet, around mouth and lips (Cats go numb)
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| what are some symptoms of high calcium levels | constipation, nausea, pain, poor appetite, vomitting, muscle twitches, weakness, etc.
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| what are the two major hormones involved in increasing calcium levels to promote homeostasis | PTH (increases blood calcium levels), calcitrol (increases calcium reabsorption in small intestine)
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| how many parathyroid glands are there and where are they located? | 4 parathyroid glands: 2 superior, 2 inferior behind the thyroid gland. macroscopic appearance as dark brown fat
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| what cells secrete PTH? | oxyphil cells and chief cells (which secrete most of the PTH)
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| what strucutres are primary target organs of PTH? | bone and kidney
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| what effect does PTH have on vitamin D synthesis in the kidney, and how does it do this? | it increases vitamin D synthesis in the kidney by stimulating 1-alpha hydroxylase activity, and it also stimulates calcium/phosphorous reabsorption.
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| what effect does PTH have on bone? | the bone has no PTH receptors on osteoclasts but PTH stimulates bone resorbing effect through RANKL. activation of RANKL promotes osteoclast differentiation and activation into mature active bone resorbing osteoclasts
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| what does RANKL stand for? | receptor activator NF-Kappa B ligand
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| what effect does PTH have on the intestines? | it has a secondary effect on calcium absorption through the activity of vitamin D.
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| what part of the intestines does calcium absorption occur? | small intestines, specifically in duodenum (acidic medium) has higher rate of calcium absorption. the largest amount of calcium absorption occurs in the ileum. but only about thirty percent of dietary calcium is absorbed.
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| active transport of calcium is activated by this | vitamin D
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| is calcium absorption more effecient in an acidic or basic environment? | acidic
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| what are some important factors of phosphorous | ATP, DNA, RNA, phosphate buffer system, phospholipids, nucleotides, covalent modificaiton, signaling molecules.
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| what two substances in the body control phosphorous regulation? | PTH, and Vitamin D
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| what is the relationship between the regulation of phosphorous and calcium? | they are very similar
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| what are the two sources of vitamin D acquired by humans? | production of it by UV radiaiton, ingested in the diet.
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| why is vitamin D not a classic hormone? | because it is not produced or secreted by an endocrine "gland", not is it a true "vitamin" because it can be synthesized de novo.
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| how is vitamin D a "true" hormone? | it acts on distant target cells to evoke responses after binding to high affinity receptors
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| where does synthesis of vitamin D take place? | vitamin D3 (previtamin D)synthesis occurs in keratinocytes in the skin.
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| describe the process of vitamin D production in the skin | vitamin D3 forms, 7-dehydrocholesterol is photoconverted to previtamin D3, then spontaneously converted to vitamin D3. previtamin D3 becomes degraded by over exposure to UV light and thus is not overproduced. also, calcitrol feedback inhibits vit D produc
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| give some examples of individuals with decreased vitamin D production | albinos, people in certain cultures, geographic locations, dark skinned people with a lot of melanin, basically people who do not get enough sun exposure.
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| what kind of receptor is vitamin D? | a steroid receptor that is fat soluble, so it doesn't work like other vitamins do.
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| calcitrol increases blood calcium in these three ways... | increases calcium absorption by the small intestine, increases calcium and phosphate resorption from the skeleton. it binds to hematopoietic stem cells and causes differentiation of osteoclasts, weakly promotes reabsorption of Ca y kidney cells
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| calcitonin is secreted from where and does what | C cells in the thyroid and lowers calcium concentration in the blood promotes deposition of calcium into bone (inhibits osteoclasts), controls the secretion of calcium from C cells.
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| this is the current standard for measuring nutritional adequacy and is composed of four reference values: EAR, RDA, AI and UL. | dietary reference intakes (DRIs)
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| this is the average daily nutrient intake level estimated to meet the requirement of half the healthy individuals in a particular life stage and/or gender group. | estimate average requirement (EAR)
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| this is the average daily dietary nutrient intake level sufficient to meet the nutrient requirement of nearly all (98%) of healthy individuals in a particular life stage and gender group. | recommended dietary allowance (RDA)
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| the recommended average daily nutrient intake level based on observe3d or experimentally determined approximations or estimates of nutrient intake by a group of healthy people. this is used when RDA cannot be determined | Adequate Intake (AI)
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| this is the highest average daily nutrient intake level likely to pose no risk of adverse health effects to almost all individuals in the general population. as intake increases above this value, the potential risk of adverse effects may increase. | tolerable upper intake level (UL)
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| why are DRIs important? | establishing nutrition standards, national school lunch programs, breakfast programs, evaluation of dietary survey data, designing nutritinoal programs. DRIs can also change.
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| defined as the availability of a vitamin in the intestines and the actual amount absorbed. a high value indicates that the vitamin is easily digested and absobed. | bioavailability
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| factors that affect bioavailability | digestion/absorption, nutritional status, food-nutrient interaction (calcium), food preparation, nutrient source
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| how much calcium and vitamin D do children need daily? | 1000mg Ca, 600IU Vit. D
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| how much calcium and vitamin D do teens need daily? | 1300 mg Ca, 600IU vit. D
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| how much calcium and Vit. D do people need between ages 51-70? | 1000mg C, 600IU vitamin D
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| what are the calcium and vitamin D recommendations for people 70 yrs and older? | 1200mg Calcium, 800 IU vitamin D
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| what are some dietary sources of calcium? | dark green leafy vegetables, sardines and canned salmon, clams, oysters, fortified foods like OJ, milk, dietary fiber...etc.
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| which calcium supplement has a higher bioavailability of calcium, calcium carbonate, or calcium citrate? | calcium carbonate
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| deficiency of calcium leads to these diseases: | osteomalacia and colon cancer
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| toxicity of calcium leads to this... | hypercalcemia, calcification in kidneys, malabsorption of other minerals such as iron, zinc, manganese
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| calcium inhibits the absorption of this mineral. that's why these vitamins should be taken at different times of the day. | iron.
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| the FDA uses this to describe the amount of calcium needed by general U.S. population daily. | "percent daily value"
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| what are some at risk populations for calcium deficiency | children and youth, post menopausal women, elderly, people with poor diets, lacking in dairy.
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| the absorption of phosphus primarily occurs in which state? | the inorganic state
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| organically bound phosphate is broken down in the intestines by these | phosphatases
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| absorption of phosphorous is dependent on this part of the stomach | the proximal part of the duodenum, which has low pH.
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| the phosphorus from vegetarian diet is received from this, which is poorly digested in humans | phytate
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| phosphorus is excreted via... | kidneys
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| is phosphorus deficiency common or rare? | rare (esp in patients taking drugs that have phosphate binders)
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| an elevation of this hormone would occur with phosphorus activity | PTH, also can result in secondary hyperparathyroidism, decrease in bone density, increase risk of fractures
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| this other mineral is found in large quantities in bones and muscles and absorption varies from one person to another but usually varies from thirty five to forty five percent | magnesium
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| absorption of magnesium typically occurs in this part of the body | the small intestine, and largest absorption occurs in the jejunum
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| what are the two mechanisms of magnesium absorption | a carrier facilitated process, simple diffusion
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| the kidneys can control the amount of magnesium by altering... | excretion
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| significant sources of magnesium are from: | seeds, nuts, logumes, milled cereal grains and dark green vegetables
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| deficiency of magnesium is rare but includes these symptoms: | tremors, muscle spasms, mood swings, anorexia, nausea, vomiting, hypocalcemia, hypokalemia, decrease levels of PTH, sodium retention
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| some problems that could potentially cause magnesium deficiency: | renal disease, diuretic therapy, malabsorption, hyperthyroidism, pancreatitis...etc.
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| vitamin D can be obtained via... | diet and de novo
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| does aging increase or decrease the body's ability to make vitamin D? | decrease. so does obesity
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| what are some food sources of vitamin D? | fatty fish, fish oils, fortified foods like milk, cereal, and breads
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| in this disease, there is a deficiency of vitamin D in children, leading to disorganization and hypertrophy of chondrocytes at mineralization front | Rickets
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| this is a vitamin D decifiency in adults, leading to mineralization defect in skeleton, poor mineralization of collagen matrix, osteopenia,...etc | osteomalacia
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| deficiency of vitamin D can lead to low calcium levels, called... | hypocalcemia
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| deficiency of vitamin D can lead to low phosphate levels...called... | hypophosphatemia
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| what are the main dietary sources of vitamin D? | fortified milk, fortified cereals, cold saltwater fish..etc. some calcium and vitamin/mineral supplements
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| how is the body able to make vitamin D? | it can be manufactured by the skin due to sunlight exposure. the amount synthesized varies with time of day, season, latitude, and skin pigmentation. 10-15 mins exposure of hands, arms, and face two to three times a week may be sufficient
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| what are some at risk populations for vitamin D deficiency? | breastfed infants, older adults, people with limited sun exposure, darker skin pigments, certain religious groups.
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| what are three vitamin D related diseases | rickets, osteomalacia, osteoporosis
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| which groups of people are at greatest risk for vitamin D deficiency? | low dietary intake: BF infants, children without access to fortified milk, malabsorption syndrome, severe liver disease, drugs, higher latitudes, people who spend little time outside, older adults, decreased sun exposure due to cultural reasons,highmelani
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| factors that influence accumulation of bone minerals are... | heredity, gender, diet, physical activity, endocrine status, maternal vitamin D status
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| some toxicities of vitamin D include: | hypercalcemia, hyperphosphatemia, calcification of soft tissues, constipation, polyuria, polydipsia, kidney stones, headache, weakness
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| rickets resuls in... | the failure of cartilage calcification and endochondral ossificaiton. the metaphyses are widened, uneven, concave, or cupped and because of the delay in or absence of calcification
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| osteoperosis can be related ot calcium loss due to the following dietary and behavioral patterns... | high meat protein diets, phosphorylated soft drinks, smoking, lack of exercise, high caffeine intake
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| some treatment of osteoperosis include: | elimination of risk factors, exercise, calcium supplements, estrogen administration
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| this disease results from a loss of bone density | osteoporosis
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| this disease results in a lack of mineralization | osteomalacia
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| vitamin D and calcium can play important roles in the prevention of these cancers | colon cancer, breast cancer
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| the recommended intake of calcium is... | 1000mg
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| the recommended intake if vitamin D is.... | 600IU
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| two main ways to increase the intake of calcium and vitamin D are... | changing diet, including supplements
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