Homeostasis is the biological process of coping with changes within and outside the body. It is the maintenance of a constant internal environment regardless of what is happening elsewhere. All organs take part in homeostasis but the key is in the excretory system which plays a major role.
Otherwise known as the Urinary system, the excretory system is made up of the Kidneys, ureter, urethra and and the bladder. It is responsible for osmoregulation; the maintenance of solutes (dissolved substances) and water regulation.
Without the excretory system we would poison ourselves with the toxic by-products of our metabolisms, or drown ourselves from the inside! This marvelous system prevents this, without allowing us to become dehydrated at the same time. It finds the perfect balance our bodies need.
From Crash Course: Biology on YouTube presented by Hank Green.