The excretory system plays a vital role in ridding the body of waste material. Although several organs are involved in this process, including the sweat glands and the lungs, it is the kidneys that are the primary organs of the excretory system.
The role of the kidneys is crucial because of the amount of water in our bodies. About sixty percent of your body contains water, which contains a precisely balanced level of salt. As the salt level of the water rises and falls, the kidneys work to remove the excess salt.
Of course, excess salt is not the only product we need to get rid of. Much like a car producing exhaust fumes, the body constantly produces waste matter as a by-product of the many processes it takes to keep us alive.
These wastes are poisonous, so if they build up and are not eliminated, they can cause problems. Thus the lungs work to expel carbon dioxide and water vapour, while other wastes such as urea, uric acid, various salts, and assorted nitrogenous wastes, are removed by the kidneys and sweat glands.
The liver also plays a role in this process, working to filter our blood, cleaning out toxic waste and acid.