Excretion
From Freepedia
Excretion is the biological process by which an organism chemically separates waste products from its body. The waste products are then usually expelled from the body by elimination.
In mammals, for example, the two major excretory processes are the formation of urine in the kidneys and the formation of carbon dioxide in the lungs. The waste products are eliminated by urination and respiration respectively. Perspiration is another excretory process which removes salts and water, although the primary purpose is cooling.
A common misunderstanding is that feces are a product of excretion. However unlike urine, fecal matter is not extracted from the bloodstream and is not part of a metabolic process.
In insects, a system involving Malpighian tubules is utilized to excrete metabolic waste. Metabolic waste diffuses or is actively transported into the tubule, which transports the wastes to the intestines. The metabolic waste is then released from the body along with fecal stuffs.
