How Water Becomes Urine
The water runs down the throat, past the epiglottis (which is closed so that water doesn't end up in the lungs) and down through the oesophagus into the stomach.
The Stomach
In the stomach, water is needed to assist in the processing and digestion of food. So far, the body has not absorbed any water. The only thing that has happened is that any thirst was probably quenched and the amount of saliva has increased.
The water and food are mixed into a dough and kneaded out into the intestines.
The Small Intestine
In the small intestine, the body starts to absorb fluid, as well as vitamins and other nutrients from the dough. These nutrients are absorbed by the blood and transported to all the body's cells.
In the small intestine, the food is so finely ground and kneaded that it is no longer firm, but rather looks like batter. After a while, this batter leaves the small intestine and continues on to the large intestine.
The Large Intestine
The large intestine's task is to absorb as much liquid as possible from the thin batter, so that the body can make use of this liquid and achieve a proper balance of body fluids. This is important, as 60% of the human body is made of water.
The Kidneys and the Bladder
The liquid is absorbed by the blood vessels in the large intestine and transported by the blood to the kidneys. In the kidneys, blood is purified and water is converted into urine which flows through the ureters to the bladder. When the bladder contains about 200 - 400ml of urine, signals are usually sent to the brain to promote urination.