What does the urinary system excrete to remove urea?

• A. Urine
• B. Blood
• C. Bile
• D. Sweat

Answer: (A)

The urinary system removes nitrogenous wastes, like urea, by forming urine. Urea is produced in the liver from ammonia during protein metabolism and travels in the bloodstream to the kidneys. In the kidneys, blood is filtered in the nephrons, waste products are collected into the urine while essential substances are reabsorbed. The resulting urine, carrying urea and other wastes, is then stored in the bladder and excreted through the urethra. This is why urine is the route by which urea leaves the body.

Sweat does remove some waste via skin but is not the primary route for eliminating urea. Bile handles digestion and waste from the liver different from urea. Blood is the transport medium carrying wastes to the kidneys, not the waste product itself.