Which organ filters water-soluble chemicals from the blood for elimination in urine?

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

Answer: (B)

The kidneys are responsible for filtering water-soluble chemicals from the bloodstream and eliminating them in urine. Blood is filtered through the glomeruli, where small, water-soluble molecules are pushed into the urine-forming filtrate. As this filtrate moves through the renal tubules, useful substances are reabsorbed while waste products and additional toxins are secreted into the urine for excretion. This makes the kidneys the primary pathway for removing many water-soluble pesticide metabolites from the body. The liver detoxifies by transforming substances to more water-soluble forms, but its products are usually cleared via the kidneys or bile, not by direct filtration for urine in the initial step. The spleen mainly filters blood cells and supports the immune system, while the intestine handles digestion and fecal waste, not the filtration of blood for urine elimination.