What is the main role of the urinary system?

The main role of the urinary system is the elimination of waste. This systems efficiently filters the blood to remove waste products and excess substances, which are then excreted as urine. The kidneys serve as the primary organs in this process by performing filtration, reabsorption, and secretion. They help maintain the body's electrolyte balance, regulate pH, and ensure that toxic substances do not accumulate in the body. By removing metabolic wastes such as urea and creatinine, the urinary system plays a crucial role in maintaining homeostasis and overall health.

The other options pertain to different bodily systems and functions; for instance, the production of blood cells is primarily associated with the bone marrow and the spleen, while defense against infections involves the immune system. Regulation of blood pressure is mainly managed by the cardiovascular system, along with hormones and the kidneys having a more supportive role through fluid balance.