There are two types of calcium. One type of calcium is tightly bound within the bone and the other more accessible type of calcium is found on the bone.
The skeleton serves as a bank of minerals for the body. 99% of the calcium in human body is stored in bones and teeth which support body structure. The remaining 1% of body calcium is found within intracellular and extracellular fluids. The body can borrow from the skeletal stores when blood calcium levels drop and return calcium to bones as needed.
A constant supply of calcium is necessary throughout our lifetime, but is especially important during phases of growth, pregnancy, and lactation (breast feeding).
Calcium is also necessary for the secretion of hormones and enzymes, for the efficient functioning of neurotransmitters and for both muscle and blood vessel contraction.
In the circulating blood, calcium concentration is typically 2.25-2.5 mmol. About 40-45% of this quantity is bound to plasma proteins, about 8-10% is complexed with ions such as citrate, and about 45-50% is dissociated as free ions.
About 10-40% of dietary calcium is absorbed in the small intestine with the help of vitamin D. The body will absorb more calcium if there is a deficiency.
Calcium in human body
