Which organ filters blood and forms urine?

• A. Liver
• B. Kidney
• C. Spleen
• D. Heart

Answer: (B)

The kidneys are the organs that filter blood and form urine. Each kidney contains nephrons, the tiny filtering units. Blood passes into the glomerulus, where water and small solutes are filtered into Bowman's capsule, creating filtrate. As this filtrate moves through the tubules, the body reabsorbs needed substances like water, glucose, and electrolytes, while waste products and excess acids are secreted into the filtrate. The resulting urine then travels from the kidneys to the bladder for excretion. The liver, spleen, and heart do not form urine—liver processes nutrients and toxins, the spleen filters blood for immune and hematologic functions, and the heart pumps blood.