How bones get their calcium

[brendan928]

I was wondering how the human body is actually able to separate the calcium from the food ingested from other unwanted minerals and it is able to get the calcium and only the calcium into the bones.

After checking wikipedia, I've found out that bones contain the compound calcium phosphate and that the stomach acid is hydrochloric acid. I also know that the calcium in bone is a base.

Thus, I'm led to believe that the separation occurs somewhere between the intestines and the bones.

I don't know much about the digestive tract after intestines but my assumption is that it goes directly into the bloodstream and is somehow absorbed into the bones.

But I'm mainly concerned about how this calcium separation happens.

If anyone can clarify this for me it would be greatly appreciated.

A college article (or research paper/journal) would also be preferable if possible but is a secondary concern.

Thanks!

Also, I'm aware that this does not apply only for humans but I was unable to find a more suitible place to put this question.

[canalon]

Basicallly the calcium used by the bones comes from the Ca++ in solution, it is absorbed in the intestine and into the bloodstream.
The regulation of the concentration of Ca++ in the blood involved numerous cells as Ca++ is not only useful to build bones, but also as a signal molecule in many different cells. But when there is enough, the cells building bones are going to be able to extract the calcium they need to build the bones and to precipitate it (make it solid) selectively to build bones.

You can start with that:
http://www.dummies.com/how-to/content/b ... by-da.html

[brendan928]

Yes, but how exactly is the calcium-and only the calcium-made to solidify? Is there a certain chemical applied to the blood that allows this, or is it a chemical property of calcium that lets it become solid since it's a metal? If there is a chemical used to solidify the calcium, what would the chemical be?

[canalon]

Cells are able to selectively conecntrate ions with protein pumps. Although it is posssible that some other metals that behave similarly to Calcium might be incorporated. But they are pobably less concentrtated in the body, and there is indeen selection of ions both by the osteoblasts and the chemical reaction causing the Ca precipitation.

[brendan928]

After checking the link and wikiing the important words, I've found that it is the Vitamin D that does something to the intestines that increases calcium absorption or something along those lines. Would this be accurate? Also, you mentioned a chemical reaction that precipitates the calcium. What exactly does the calcium react with and is it only the calcium compound that is precipitated?