The Excretory System
More Parts of the System
After blood exits the kidneys, it still contains the metabolic waste carbon dioxide. This blood flows to the lungs, where the carbon dioxide in the blood is exchanged for the oxygen in the lungs through the alveoli, small structures that facilitate gas exchange.The carbon dioxide is then removed from the body by the contractions of the lungs which force the waste out through the mouth and nose. The lungs are vital to the Excretory System because they dispose of the only remaing waste in the blood after it flows to the kidneys: carbon dioxide.
Source: http://www.ihaelth.com/lung-diagram-with-labels/
The skin is also involved in the excretory system because it contains sweat glands and ducts. These structures that are located beneath the skin secrete perspiration, also known as sweat. Sweat contains some of the same components as urea, which means that the skin also excretes metabolic wastes from the body. However, this is not the main function of these sweat glands. Their main function is to regulate temperature and salt concentration within the body.
Source: http://fromyourdoctor.com/topic.do?title=Dermatology+Glossary+D&t=11411