This document discusses the relationship between water and excretion. It defines excretion as the process by which the body separates and removes waste. Several organs are involved in excretion, including the kidneys, urethra, bladder, skin, and liver. The kidneys filter waste from the blood into urine, while the urethra and bladder transport urine out of the body. The skin excretes salts and heat through sweat. The liver converts ammonia into urine. Water plays a key role, as it carries waste through the organs and is a main component of urine, sweat, and other excretions. Without water, the excretory system could not function properly to remove waste from the body.