Which organs are primarily responsible for filtering waste from the blood and forming urine?

The kidneys are primarily responsible for filtering waste from the blood and forming urine. They perform this vital function through a process called nephron filtration, where blood passes through thousands of tiny filtering units known as nephrons. Within each nephron, waste products, excess salts, and water are filtered out of the blood, while essential substances, such as nutrients and proteins, are reabsorbed back into the bloodstream.

Once the waste products are filtered, they enter the renal tubules, where further processing occurs to regulate the body’s water and electrolyte balance. The final product, urine, is then transported to the bladder via the ureters, where it is stored until excretion.

Other organs mentioned play different roles in the body: the liver is primarily involved in detoxifying substances and metabolizing nutrients; the lungs facilitate gas exchange, removing carbon dioxide and providing oxygen; and the spleen is part of the lymphatic system and plays a role in filtering blood, but its primary function is related to immune response and recycling iron from erythrocytes, not waste filtration and urine formation. Thus, the kidneys are the key organs in the filtration process that leads to urine production.