Which organ is primarily involved in filtering blood and producing urine?

The kidney is the organ primarily responsible for filtering blood and producing urine. This vital function is accomplished through a complex system of nephrons, the functional units of the kidney. Each nephron filters blood plasma, removing waste products, excess substances, and toxins while retaining essential compounds like proteins and cells.

As blood passes through the glomerulus, a network of capillaries within the nephron, filtration occurs. The resulting filtrate then undergoes further processing in the renal tubules, where substances can be reabsorbed back into the bloodstream or secreted into the urine. This process not only helps eliminate waste but also plays a critical role in maintaining homeostasis, including regulating blood pressure, electrolyte balance, and acid-base balance.

The liver, while involved in metabolism and detoxification, does not have a direct role in urine production. The heart is responsible for circulating blood throughout the body, and the lungs facilitate gas exchange, not blood filtration. Therefore, the kidney is essential for these specific functions related to urine production and blood filtration.