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How do bones store calcium and phosphate for the body?
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skeleton
Selected vertebrate skeletons.
Bones serve as the primary reservoir for the body's calcium and phosphorus, housing approximately 99 percent of total body calcium and 85 percent of total body phosphorus within their mineral deposits.3
Storage and Mineralization
These minerals are stored in the form of hydroxyapatite crystals, which are deposited into the collagen matrix of the bone. During bone mineralization, osteoblasts secrete matrix vesicles containing calcium and phosphate ions, which act as nucleation sites for crystal formation.12
Regulation and Release
Bone acts as a dynamic buffer to maintain stable ionic concentrations in the blood. This process is regulated by hormonal control loops involving parathyroid hormone, calcitonin, and vitamin D:3
- Resorption: When blood calcium levels are low, osteoblasts recruit osteoclasts, which secrete hydrochloric acid and enzymes to dissolve bone mineral, releasing calcium and phosphorus into the circulation.34
- Deposition: When calcium needs are met, osteoblasts increase bone formation and mineralization, effectively storing excess ions back into the bone matrix.35