<P> The excretory system is a passive biological system that removes excess , unnecessary materials from the body fluids of an organism , so as to help maintain internal chemical homeostasis and prevent damage to the body . The dual function of excretory systems is the elimination of the waste products of metabolism and to drain the body of used up and broken down components in a liquid and gaseous state . In humans and other amniotes ( mammals , birds and reptiles ) most of these substances leave the body as urine and to some degree exhalation , mammals also expel them through sweating . </P>
the function of the excretory system is to help maintain homeostasis by
removes excess , unnecessary materials from the body fluids of an organism