Is there a difference between renal system and urinary system? Or are they the same but have different names?
I would say both words are used in case of vertebrate anatomy and physiology. Renal or urinary system could be actually termed as excretory system.
Nitrogenous waste products of animals are excreted by various organs which form excretory system.
Few examples of excretory organs of different groups of animals are as follows:
Malpighian tubules in insects,
Green gland in prawns/cray fishes,
Nephridia in annelidan worms,
Flame cells and tubules in flat worms,
Kidneys in vertebrates.
The word 'RENAL' has Latin origin, which means 'related to kidneys'. The kidneys are excretory organs of vertebrates.
In vertebrates blood is filtered in kidneys and the excretory product is not always liquid as it is in case of mammals.
The liquid excretory product of renal system in mammals, including man, is called urine. Thus excretory system in such animals is often termed urinary system.