Term
| What organ helps regulate Ca+2 serum concentration? |
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Definition
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Term
| What glands help regulate Ca+2 serum concentration? |
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Definition
Parathyroid glands (they respond to LOW levels of serum calcium)
NOTE:thyroid gland produces calcitonin in responds to HIGH levels, but no known effect |
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Term
| What is the normal serum Ca+2 concentration level? |
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Definition
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Term
| What are the 2 types of bone? |
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Definition
1: Cortical (or lamellar) bone: skull, shafts of long bones
2: trabecular (or cancellous): distal radius, vertebral bodies, trochanter |
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Term
| What are the bone sites where trabecular (or cancellous) bone predominates? |
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Definition
| greater trochanter neck of the femor vertebrae the distal radius |
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Term
| What is so important about trabecular (or cancellous) bone? |
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Definition
| most osteoporotic fractures occur at sites in which trabecular bone predominates |
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Term
| Bone is completely replaced (remodeled) every ________ years. |
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Definition
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Term
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Definition
| Synthesize components of bone scaffolding into which bone regenerates |
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Term
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Definition
| resorb (or remove) old bone |
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Term
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Definition
| sense biomechanical strain within bone and communicates with osteoblasts (signaling when and where new bone is needed) and osteoclasts (signaling when and where old bone needs to be removed) |
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Term
| What are osteoclasts made of? |
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Definition
| macrophages that fuse together and form a sealing zone over the bone surface |
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Term
| Ca+2 fluxes in and out of extracellular fluid via what 3 routes? |
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Definition
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Term
| What is the normal daily intake of calcium? |
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Definition
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Term
| How much of the dietary calcium intake actually ends up being absorbed? |
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Definition
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Term
| Where is the majority of calcium excreted? |
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Definition
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Term
| What is parathyroid hormone (PTH)? |
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Definition
| A hormone secreted by the parathyroid glands in response to low serum calcium levels |
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Term
| What responses occur in the body in response to PTH secretion? |
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Definition
| 1: kidneys hold on to more calcium 2: osteoclasts resorb more bone (i.e., they pull Ca+2 from bone into blood) 3:GI absorbs more calcium |
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Term
| What happens in the kidney in response to PTH? |
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Definition
| 1: renal secretion of calcium is inhibited 2: Phosphate and bicarbinate reabsorption are inhibited proximal tubules stimulated to produce more active form of vitamin D |
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Term
| What happens in the skeleton in response to PTH? |
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Definition
1: Activation of osteoclastic bone resorption to mobilize calcium
2: over the long term, it also stimulates osteoblasts to produce new bone, thereby removing calcium from blood |
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Term
| How many parathyroid glands are there? |
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Definition
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Term
| Where are the parathyroid glands? |
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Definition
| located behind the normal thyroid lobes, two on each side |
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Term
| What vitamin is associated with PTH? |
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Definition
| PTH helps to produce the active form of vitamin D. |
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Term
| What are the 2 forms of vitamin D? |
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Definition
| D2 (ergocalciferol) and D3 (cholecalciferol) D2 is derived from plant sterols D3 is derived primarily from sunlight on skin |
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Term
| What is the difference between phosphate and phosphorus? |
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Definition
| Phosphorus is a neutral, inorganic element Phosphate is a biologically active, negatively charged ion which contains phosphorus the terms are often used interchageably (unfortunately) |
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Term
| Is phosphate primarily an intracellular or extracellular ion? |
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Definition
| It is primarily INTRAcellular, but both have function. |
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Term
| What does the EXTRAcellular phosphate do? |
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Definition
| Pairs with calcium to provide structural integrity to the skeleton. |
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Term
| What is the normal serum level of phosphorus? |
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Definition
| 3.0 to 4.5 mg/dL. NOTE that it is PHOSPHORUS, not PHOSPHATE level that most labs measure. |
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Term
| What is the relationship of phosphate to the pH of blood? |
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Definition
Phosphate is a very important buffer, helping to keep the blood pH WNL.
In metabolic acidosis, phosphate leaves the cells and enters the blood to buffer the acid.
In metabolic alkalosis, phospate leaves the blood and enter the cells. |
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Term
| Where within the GI system is phosphous absorbed? |
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Definition
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Term
| What circumstances could lead to phosphorus deficiency? |
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Definition
| Alcoholism ICUs without adequate oral or parenteral nutrition intestinal malabsorption phosphate-binding antacid use [NOTE that most diets are adequate in phosphorus] |
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Term
| Where is phosphate stored? |
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Definition
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Term
| Name 3 important ways calcium is used in the body. |
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Definition
| 1- muscle and nerve membrane excitability 2-skeleton 3- intracellular signaling |
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Term
| What organ is most responsible for the regulation of calcium levels in the body? |
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Definition
| Kidneys. They reabsorb about 90%, then work with the remaining 10% to adjust the levels based on body need at the moment. |
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Term
| About how much calcium (kg) is actually contained in the human skeleton? |
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Definition
| Men: 1.2 kg; women 1.0 kg |
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Term
| What is the purpose of "active" vitamin D in the body? |
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Definition
| It regulates intestinal calcium absorption (the more active Vitamin D, the more calcium is absorbed in the intestines). To a lesser extent, it also promotes absorption of phospate in the intestine. |
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Term
| What is the liver's involvement with vitamin D? |
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Definition
| The liver converts one precursor form of vitamin D to another precursor form, which the kidneys will then convert to the active form of vitamin D. Severe liver failure can prevent that precursor step, which can lead to low vitamin D levels. |
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Term
| What is the form of vitamin D that is measured in labs? The active form, or a precursor form? |
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Definition
| The inactive precursor form that is formed in the liver is what is measured in lab tests. |
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Term
| What activity regulates phosphate entry and exit from skeletal bone? |
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Definition
| Osteoclast and osteoblast activity regulates the entry and exit of phosphate from the skeleton. Phosphate moves along with the calcium in and out of the bone (i.e., it is a "passive passenger"). |
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Term
| What disease processes can lead to hypophosphatemia? |
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Definition
Osteoblastic metastasis in prostate cancer and breast cancer, and the "hungry bone syndrome" that can develop following parathyroidectomy all lead to clinically significant hypophosphatemia.
Chronic alcoholism can also lead to dietary phosphate deficiency. |
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Term
| What disease processes can lead to hyperphosphatemia? |
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Definition
| Skeletal destruction in multiple myeloma or severe immobilization syndromes can lead to both hypercalcemia and hyperphosphatermia. Basically, the diseases are "eating" the bone, throwing the remnants into the blood. |
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Term
| What problems can hypercalcemia and hyperphosphatemia cause? |
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Definition
| Nephrocalcinosis and renal failure. |
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Term
| How is PTH related to phosphate levels? |
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Definition
| PTH inhibits renal reabsorption of phosphate in the renal tubules. |
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Term
| What are the differences between how the body regulates magnesium as compared to phosphate? |
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Definition
| There's not much difference; the regulation of both are pretty much the same. Note, however, that magnesium is a CATION (Mg+2) in the body, while phospate is an ANION (PO4-3). |
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Term
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Definition
| skeletal muscle weakness, smooth muscle hypoactivity, mental dysfunction, renal dysfunction, decreased GFR, renal stones, shortening of QTc on ECG |
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Term
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Definition
| hyperexcitability of neurons (spontaneous seizures, parasthesias) and muscles muscle spasm, tetany |
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Term
| What does calcium have to do with nerves? |
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Definition
| It regulates the nerve excitability. Too MUCH calcium outside the cell (i.e., in the blood) makes it HARDER to excite the nerve==>muscular weakness==>coma. Too LITTLE calcium outside the cell makes it EASIER to excite the cell==>convulsions, muscle cramps, contractions (tetany). |
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Term
| What does calcium have to do with bone? |
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Definition
| It is the major structural cation in the bone. Too little calcium in the bone leads to spontaneous fractures. |
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Term
| What does calcium have to do with cells? |
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Definition
| Calcium is a signaling tool inside cells. Without it, those signals don't get processed inside the cells. |
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Term
| What does it mean to say that osteoclasts "resorb" bone? |
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Definition
It means osteoclasts remove bone tissue by removing the mineralized matrix and breaking up the organic bone.
Osteoclasts basically "eat" bone tissue. |
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