Ca is the most abundant mineral in the body.
Ca homeostasis involves a system of hormones and vitamin D.
Whenever blood Ca falls too low or rises too high, 3 organ systems organ systems
respond: the intestine, bone, and kidney.
Ca in bone provides a nearly inexhaustible bank of Ca for the blood.
The blood borrows and returns Ca as needed so that even with a
dietary deficiency, blood Ca remains normal dietary deficiency, blood Ca remains normal—even as even as bone Ca bone Ca
diminishes.
Blood Ca above normal Ca above normal results in results in Ca rigor: the muscles contract and
cannot relax.
Blood Ca below normal Ca below normal causes Ca tetany: uncontrolled muscle
contraction.
On average, adults absorb about On average, adults absorb about 25% of the Ca the % of the Ca they ingest. y ingest.
The stomach’s acidity helps to keep Ca soluble, and vitamin D helps to
make the make the Ca-binding protein binding protein needed for absorption. needed for absorption.
Ca participates in the regulation of muscle contractions, the blood
clotting, the transmission of nerve impulse, the secretion of hormone,
and the activation of some enzyme reactions