What are the three main functions of the urinary system?

The three main functions of the urinary system are excretion, secretion, and elimination. Excretion refers to the removal of waste products from the bloodstream, which is primarily accomplished by the kidneys filtering blood and generating urine. Secretion involves the active transport of certain substances into the tubular fluid, which can include ions, acids, and drugs, playing a crucial role in maintaining homeostasis. Elimination is the final stage where urine, containing the filtered wastes, is expelled from the body through the urinary tract.

This understanding highlights the urinary system's vital role in regulating the body's internal environment by controlling the volume and composition of bodily fluids, ensuring that harmful substances are efficiently removed from the body. The other options do not fully encompass the primary functions of the urinary system or incorporate functions that are unrelated to typical urinary processes.