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Calcium Homeostasis
| Question | Answer |
|---|---|
| what does calcium homeostasis depend on? | depends on a balance between dietary intake, urinary & fecal losses, & exchanges with the osseous tissue |
| what 3 hormones regulate calcium? | calcitonin, parathyroid hormone (PTH) & calcitriol |
| calcitonin | *if blood Ca conc. incr, then incr. calcitonin* secreted by C cells of the thyroid gland. It is secreted when blood Ca concentration rises too high, functions to lower concentration *think "calci tone it down" |
| what two principle mechanisms does calcitonin use to lower blood Ca concentration? | decr. osteoclast activity (which liberates less calcium from skeleton) incr. osteoblast activity (they promote deposition of calcium into skeleton by forming osteoid which gets hardened. |
| Parathyroid Hormone | PTH: secreted by parathyroid gland. It is secreted when blood Ca conc. drops too low; functions to raise conc. |
| what four principle mechanisms does PTH use to raise blood Ca concentration? | -stimulate osteoclasts (promotes bone resrption & liberates Ca from bones into blood plasma) -incr dietary uptake of Ca from intestines -incr. Ca reabsorption from filtrate in kidnys -promotes final step of calcitriol synthsis in kidneys |
| Calcitriol | the active form of vitamin D produced by sequential action of the skin, liver & kidneys. It behaves like a hormone in the blood, and its principal function is to raise blood Ca conc. |
| what 3 mechanisms does calcitriol use to raise blood Ca conc? | -incr. osteoclast activity (promotes bone resorption & liberates Ca & phosphate from bones into blood) -incr. Ca & phosphate absorption by the smalll intestine -decr. urinary secretion of ca and phosphate (less ca lost in urine) |
| where can we find vitamin D? | UV light, vitamin pills, fortified milk, liver, egg yolks, butter & cheese |
| explain synthesis of vitamin D? | the first step of vitamin D synthesis is carried out in skin. skin cells exposed 2 sun use UV light to convrt a steroid into vit D3 (inactive). goes 2 liver where a hydroxyl group added, and changed again in the kidneys: convrts 2 actve form =calcitriol |
| basic function of kidneys? | filter-->reabsorb-->secrete |
| which hormone functions to decrease blood ca concentration? | calcitonin |
| which hormone(s) function to increase blood ca concentration? | Parathyroid hormone (PTH) and calcitriol (active vitamin D) |
| Rickets | insufficient vitamin D in kids. |
| what does Rickets result inside body and what are physical ramifications | a disease resulting in reduced mineralization of organic matrix of bone. so kid will have bowed bones and inflamed joints (i.e. growth plates) *think: not enough vitamin D = not enough calcium = not enough hardening/calcification of bone |
| Osteomalacia | insufficient vitamin D in adults. |
| what does Osteomalacia result inside the body? | a disease where you have softening of the bones as a result of Ca depletion (excess accumulation of osteoid) *think: not enough vitamin D = not enough calcium = not enough hardening/calcification of bone |
| Osteoporosis | when bone resorption outpaces bone deposit. (i.e. osteoclasts work harder than osteoblasts) Most common bone disease |
| what do Rickets & Osteomalacia have in common | insufficient vitamin D leads to calcium depletion, leads to insufficient bone deposition/mineralization of the skeleton |
| how is Osteoporosis different from Rickets & Osteomalacia? | its not a problem of insufficient bone deposition, just that bone resorption happens to be outpacing it |
| what does Osteoporosis lead to in body? | bones become more porous & lighter. spongy bone in the spine is most vulnerable, and this will lead to compression fractures. |
| estrogen & testosterone.. | help restrain osteoclasts |
| explain a digestive disorder that may lead to Osteomalacia | some people have a hard time absorbing fats. If this is the case you won't absorb vitamin D into the body well since it is a fat soluble vitamin. So if u can't absorb Vit D from small int. you can't absorb Ca either, leads 2 calcium depletion/osteomalacia |
Created by:
kalmetina
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