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The Urinary System
The function of the excretory organs is just as essential to the well-being of the body as those of the other body systems.
Like the world in which we live, the human body has its pollution problems. Nutrients, taken in through the digestive system, and oxygen, supplied by the inhaled air, are utilised to provide the energy needed to power the activities of the body. But the metabolic processes, like those in huge factories, generate by-products and wastes. To prevent the body from polluting itself-with its own waste products they, must be eliminated as they are produced. The excretory organs and the major substances they eliminate are summarized below :
Excretory Organs Substances Excreted Lungs
Gaseous wastes, carbon
dioxide, water vapour Skin (sweat glands) Water, salts, nitrogenous
wastes Alimentary canal Solid wastes of digestion (large intestine) Kidneys
Water, nitrogenous wastes, soluble salts, bacterial toxins, infested drugs and poisons, etc.
We have already dealt with the excretory functions of the lungs, skin, and large intestine. We shall, therefore, discuss here the kidneys together with the other organs of the urinary system. The alimentary canal is not the main waste disposal system, but the urinary system is. The former may become inactive for quite some time without
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