Function of Calcium

Calcium, a common and essential mineral in the human body, is mostly found in the teeth and bones; only 1% is located in the soft tissue and blood.

The levels of calcium in the extracellular fluid (fluid surrounding the cells) as well as in the blood need to be kept within a very narrow concentration range for normal physiological function.

Function of Calcium

The biological function of calcium is very significant for the body to survive as the body will demineralize bone to maintain normal blood calcium levels in conditions when calcium consumption is not sufficient. Calcium is stored in the body in two ways:

  1. In the exchangeable pool that allows this mineral to be released in the blood stream in times wherein the dietary intake is too low, and
  2. The rest of the calcium is kept in the non-exchangeable bone reserves.

The bone’s mineral component is made of hydroxyapatite crystals that contains huge amount of the mineral and of phosphate.

The osteoclasts, also known as the bone cells, start the process of remodeling by reabsorbing or dissolving bone as the bones are dynamic tissues that is being remodeled constantly in life.

The osteoblasts, the bone-forming cells, will be synthesizing new bones to substitute for the bone that was resorbed. Bone formation exceeds bone resorption during normal growth as osteoporosis could arise whenever bone resorption recurrently exceeds such formation.

The role of calcium

Calcium plays a significant role in the relaxation and contraction of vasodilation and vasoconstriction of the blood vessels, muscle contraction, nerve impulse transmission, and the hormone secretion such as insulin. Nerve cells, skeletal muscle and other excitable cells contain voltage-dependent calcium channels for rapid changes in the concentrations of calcium.

Calcium is also vital in stabilizing a number of enzymes and proteins that will be optimizing their functions, making calcium a cofactor for proteins and enzymes. The binding of calcium ions is needed for the stimulation of the clotting factors, the seven “vitamin K-dependent”, in the coagulation cascade. This process, the coagulation cascade, denotes on the chain of events that is dependent with each other.

The concentrations of calcium in the fluid that surrounds the cells and in the blood are closely managed for the preservation of normal physiological function. In cases of insufficient intake of calcium, once the blood calcium level decreases, the calcium-sensing proteins in the parathyroid glands will be sending signals that will result in the parathyroid hormone (PTH) secretion. The parathyroid hormone is stimulating the conversion of vitamin D to calcitriol, which is its active form in the kidneys.

This active form upsurges the calcium absorption from the small intestine. Calcitrol, along with PTH, stimulates the calcium release from bones by activating the bone resorbing cells, the osteoclasts, and decreasing the calcium urinary excretion through its increased reabsorption in the kidneys. The parathyroid glands will discontinue the secretion of PTH once the calcium levels in the blood rises to normal levels.

Adequate consumption of calcium is highly important that is why there is a revised Recommended Dietary Allowance for calcium that needs to be observed. Visit these pages for information of Calcium rich foods and for a list of calcium rich foods.

References and Further Reading

LPI; Orchard; Wikipedia.