No fasting is required prior to this test. The test evaluates how your body processes sugar. A high level in your blood may indicate your body is not processing sugar effectively (positive test). If the results of this screen are positive, the woman may have the Glucose Tolerance Test performed.
A valve is a mechanism that opens and closes to control the flow of fluids. In a scientific context, fluids include both liquids and gases â any substance that can flow freely â and valves may use either. Valves control fluid flow in motors, plumbing, irrigation, pneumatic and hydraulic systems.
Definition of valve for Students. 1  1 : a structure in the body that temporarily closes to prevent passage of material or allow movement of a fluid in one direction only a heart valve. 2  2 : a mechanical device by which the flow of liquid, gas, or loose material may be controlled by a movable part.