Calcium and phosphorus are the most abundant inorganic elements in the human body. Approximately 99% of calcium and 86% of phosphorus exist in the form of hydroxyapatite within bones and teeth, while the remainder is distributed in dissolved form within bodily fluids and soft tissues. Blood calcium refers to the total calcium present in serum, with a normal concentration of 2.25–2.75 mmol/L in adults. Phosphorus in the blood exists in both organic and inorganic forms, and blood phosphorus typically refers to the inorganic phosphorus in plasma, with a normal concentration of 1.1–1.3 mmol/L in adults.
The primary physiological functions of calcium include the formation and maintenance of bone and tooth structures, supporting normal cell functions, regulating cellular processes and enzyme activities, maintaining neuromuscular excitability, and participating in the coagulation process. Phosphorus is an essential component of nucleic acids within all cells of the body, a critical structural element of cell membranes, and an indispensable component in processes such as metabolism, skeletal structure, and fluid composition. Phosphorus is involved in the body's energy metabolism and regulates the activity of biological macromolecules. Phosphates also constitute a vital part of the blood buffering system.
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