What organ filters blood to produce urine?

The kidneys are essential organs in the urinary system responsible for filtering blood to produce urine. Their primary function is to remove waste products and excess substances from the bloodstream, which helps regulate body fluids, electrolytes, and acid-base balance. The kidneys contain millions of tiny filtering units called nephrons, which play a crucial role in this filtration process. As blood flows through the nephrons, waste products and excess substances, such as urea and creatinine, are filtered out, while essential components like glucose and certain ions are reabsorbed back into the bloodstream. The filtered waste is then excreted as urine.

The liver primarily processes nutrients and detoxifies various metabolites, but it does not filter blood in the same way as the kidneys. The lungs are involved in gas exchange, not in the filtration of blood to produce urine. The bladder serves as a storage organ for urine before it is excreted from the body, but it does not participate in the filtration process. Therefore, the kidneys are the correct answer, as they are specifically designed for filtering blood to create urine.