Which mineral is primarily stored in bones?

• A. Sodium
• B. Potassium
• C. Calcium
• D. Iron

Answer: (C)

Calcium acts as the mineral stored in bones, forming the rigid framework of the skeleton through calcium phosphate crystals. About 99% of the body's calcium in adults sits in the bones, serving as a reservoir that can be drawn upon to maintain blood calcium levels. When blood calcium is needed for essential functions like muscle contraction, nerve signaling, and blood clotting, hormones trigger bone resorption to release calcium. Sodium and potassium are primarily found in body fluids where they support nerve and muscle function, not in bone as major storage. Iron is mainly stored in the liver and spleen as ferritin and hemosiderin for making hemoglobin, not in bone. So calcium is the mineral primarily stored in bones.