the brain
they remove waste products from the body that might otherwise be harmful, like urine, or waste products from the digestive system.
excretory organ (an organ that separates waste substances from the blood and discharges them)
A respiratory organ would be an organ that aids in the process of respiration/breathing i.e. the lungs. An excretory organ is an organ that aids in the process of excreting urine or feces i.e. the...
that is because Excretion is the process of eliminating waste products of metabolism and other non-useful materials