Which organ is primarily responsible for filtering blood and forming urine?

• A. Liver
• B. Kidneys
• C. Lungs
• D. Pancreas

Answer: (B)

Kidneys are the organs that filter the blood and form urine. They host nephrons, the tiny filtering factories where blood is first filtered at the glomerulus to make a filtrate. This filtrate then moves through tubules where most water, electrolytes, and nutrients are reabsorbed, while wastes like urea and some ions are secreted into the filtrate to become urine. This system keeps body fluids balanced, maintains electrolyte and acid-base harmony, and helps regulate blood pressure. Other organs have different primary roles: the liver detoxifies and metabolizes substances, the lungs exchange oxygen and carbon dioxide, and the pancreas produces digestive enzymes and bicarbonate. Thus, the kidneys are the ones chiefly responsible for filtering blood and forming urine.