Research work · 2024
Excretory systems
Ariel D. Chipman
Oxford University Press eBooks
Abstract
Abstract Excretory systems have two separate roles: elimination of waste products and maintaining a correct ion balance. Waste products are mostly breakdown products of nitrogenous compounds, which include toxic ammonia. The excretory system has to detoxify and remove ammonia to prevent it from accumulating in tissues. Maintaining ion balance, or osmoregulation, involves selectively removing excess ions and water or both to maintain a level of salinity of the tissue fluids that is similar to that of sea water. The simplest excretory organs are protonephridia. These are single-cell structures that draw water and small molecules from the body fluids and remove excess material as urine. Metanephridia are multicellular structures that draw fluids into a lumen and return necessary components back to the body, removing the excess as urine. Terrestrial arthropods have a third type of excretory organ, known as Malpighian tubules—these remove excess ions from the body fluids and transfer them to the digestive system for removal.