History and Uses: Although calcium is the fifth most abundant element in the earth's crust, it is never found free in nature since it easily forms compounds by reacting with oxygen and water.Metallic calcium was first isolated by Sir Humphry Davy in 1808 through the electrolysis of a mixture of lime (CaO) and mercuric oxide (HgO).ther common compounds of calcium include: calcium sulfate (CaSO 4), also known as gypsum, which is used to make dry wall and plaster of Paris, calcium nitrate (Ca(NO 3) 2), a naturally occurring fertilizer and calcium phosphate (Ca 3 (PO 4) 2), the main material found in bones and teeth.
incretin: A gastrointestinal hormone causing an increase in the amount of insulin released from the beta cells of the islets of Langerhans after eating, even before blood glucose levels become elevated.
There are two main incretin hormones in humans, GIP (glucose-dependent insulinotropic peptide; also known as gastric inhibitory peptide) and GLP-1 (glucagon-like peptide-1). Both hormones are secreted by endocrine cells that are located in the epithelium of the small intestine.ncretin hormone release is regulated in a similar way to other digestive tract hormones. An increase in the concentration of a substance in the lumen of the digestive tract (in this case glucose) acts as the trigger for hormone secretion. The mechanism of incretin action is schematized in the figure below.