A Fluid is a substance that has no fixed shape and continually deforms/flows when external force is applied on it. Fluids are a phase of matter that include liquids, gases and plasmas. Liquids form a free surface (that is, a surface not created by the container) while gases do not.
Examples of a fluid can be oxygen, water, and even air! Not only do we use fluids, such as air and water, to stay alive, the human body is mostly made of fluids. Each of us is about 60–70 % water. Table 2 shows other fluids our bodies make and use.
How does dialysis work?
Sometimes technology is needed to maintain the health of our bodies’ fluid systems. Our body cells produce waste continuously. This waste is carried in the bloodstream and could harm or kill us if it were not removed. For people whose kidneys do not work properly, a dialysis machine performs this function (Photo on the left). Blood flows through a tube into the machine, is cleaned, and then returns to the body. Each dialysis treatment takes four to five hours.