Gastrointestinal: Adjective referring collectively to the stomach and small and large intestines. The commonly used abbreviation for gastrointestinal is GI. (Outside of medicine, GI can also stand for galvanized iron, general issue or government issue-as in GI Joe).
Before the extracellular matrix is calcified, the tissue is called osteoid (bone-like) tissue. When the concentrations of calcium and phosphate ions rise high enough, they are deposited into the extracellular matrix, and the bone calcifies.
An oolite is a sedimentary rock formed of spherical grains conposed of concentric layers, called ooids (egg stones). Once an ooid grows beyond 2 mm it is called a pisolite (Figure 8-40) . Ooids and pisolites are a commonly composed of calcite or hematite, but can form from other minerals.