The excretory system is how metabolic wastes and foreign wastes are passed through,or excreted,from the body. Many organs are involved in the excretory system, including the skin, lungs, liver and kidneys. During the excretory system wastes will be extracted from blood, and other bodily fluids. The excretory system also helps the body to maintain homeostasis. By extracting wastes and other harmful molecules it helps our bodies stay at a constant and healthy waste levels. During the excretory system carbon dioxide salts and other molecules will be taken out of our bodies. The main goals of the excretory system are to: get rid of wastes, eliminate useless by-products, eradicate harmful chemical build ups and to maintain a steady balanced chemical concentration. The excretory system interacts with many other body systems, including the Digestive and the Respiratory systems. In the digestive system food is broken down into smaller molecules so that out cells can use them. Foods will also contain some molecules that cannot be used by cells. The blood carries these wastes or extra molecules and takes them to the lungs.(The Respiratory System) When there is a buildup of these wastes your body will exhale these molecules, which is part of the excretory system because wastes are being extracted from the body. Also in the Circulatory system blood is being transferred to various organs in the body. These organs will then process the blood which is part of the excretory system.