Urination is the process by which the body expels liquid waste, primarily composed of water, urea, and other substances. This process occurs in the kidneys, which filter blood to remove waste products. The filtered waste is then stored in the bladder until it is ready to be released. When the bladder fills, nerve signals prompt the urge to urinate. The brain then coordinates the relaxation of the sphincter muscles to allow urine to flow through the urethra and out of the body. This process is essential for maintaining the body's fluid balance and removing toxins.