ABSTRACT
This chapter considers the physiology of the generalized excretory organs. Excretory organs are involved in the removal of the waste products of metabolism, such as the breakdown products of nitrogen metabolism, and the removal of exogenous substances, such as drugs in humans. Generalized excretory organs include such structures as contractile vacuoles and various types of tubular structures, e.g. nephridial organs, Malpighian tubules and nephrons. Contractile vacuoles are the excretory organs of the coelenterates and the protozoans. Protonephridia are excretory structures which exist as closed or blind-ended, tubules and which do not connect with the coelomic cavity. Metanephridia, sometimes called nephridia, are the organs of excretion found in many annelid worms. Malpighian tubules are the excretory organs of the insects. Crustaceans have excretory organs called green or antennal glands, located in the head region. The principal excretory organ of the vertebrates is the kidney, the functional unit of which is the nephron.
