Editing Calcium

[[file:Ca(aq)6_improved_image.tif|thumb|left]] [[file:Ein_Ghazal_Venus.jpg|thumb|left]] [[file:Pamukkale_Hierapolis_Travertine_pools.JPG|thumb|right]] [[file:Calcium_intake_world_map.svg|thumb|right]] '''Calcium''' is a [[chemical element]] with the symbol '''Ca''' and [[atomic number]] 20. It is an [[alkaline earth metal]] and is the fifth most abundant element by mass in the [[Earth's crust]]. Calcium is essential for living organisms, particularly in cell physiology, where movement of the calcium ion Ca²⁺ into and out of the [[cytoplasm]] functions as a signal for many cellular processes.

== Properties ==
Calcium is a soft gray metal that is an essential constituent of [[teeth]] and [[bones]]. It is the fifth most abundant element in the [[human body]] and the most abundant metal by mass in many animals. Calcium ions play a vital role in the physiology and biochemistry of organisms and cells, particularly in signal transduction pathways, where they act as a second messenger, in [[neurotransmitter]] release from neurons, in contraction of all muscle cell types, and in fertilization.

== Occurrence ==
Calcium does not occur naturally in its elemental state but is found in various [[minerals]] such as [[calcite]], [[dolomite]], and [[gypsum]]. It is also a major component of [[limestone]], which is used in the production of [[cement]] and [[concrete]].

== Biological Role ==
Calcium is crucial for many physiological functions. It is a key component of [[bone]] and [[tooth]] structure, where it is present as [[calcium phosphate]] in the form of [[hydroxyapatite]]. Calcium ions are also important in [[blood clotting]], [[muscle contraction]], and [[nerve function]].

=== Bone Health ===
Calcium is stored in bones and teeth, where it supports their structure and hardness. The body needs calcium to maintain strong bones and to carry out many important functions. About 99% of the calcium in the body is in bones and teeth. The remaining 1% is found in blood, muscle, and other tissues.

=== Cellular Functions ===
Calcium ions play a crucial role in many cellular processes. They are involved in the release of [[neurotransmitters]] at synapses, the contraction of muscle cells, and the regulation of enzyme activity. Calcium ions also act as a second messenger in many signal transduction pathways.

== Dietary Sources ==
Calcium can be obtained from various dietary sources. [[Dairy products]] such as [[milk]], [[cheese]], and [[yogurt]] are rich in calcium. Other sources include [[leafy green vegetables]], [[nuts]], and [[fish]] with edible bones such as [[sardines]] and [[salmon]].

== Deficiency ==
A deficiency in calcium can lead to various health issues, including [[osteoporosis]], a condition characterized by weak and brittle bones. Symptoms of calcium deficiency include muscle cramps, numbness, and tingling in the fingers, and abnormal heart rhythms.

== Supplementation ==
Calcium supplements are available for individuals who do not get enough calcium from their diet. These supplements come in various forms, including [[calcium carbonate]] and [[calcium citrate]]. It is important to take calcium supplements as directed by a healthcare provider to avoid potential side effects such as kidney stones.

== See Also ==
* [[Magnesium]]
* [[Phosphorus]]
* [[Vitamin D]]
* [[Bone mineral density]]
* [[Parathyroid hormone]]

== References ==
{{Reflist}}

== External Links ==
{{Commons category|Calcium}}
{{Wiktionary|calcium}}

[[Category:Chemical elements]]
[[Category:Alkaline earth metals]]
[[Category:Essential minerals]]
[[Category:Nutrition]]
[[Category:Bone health]]

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