The urinary system is a very important system in the human body. The urinary system is composed of the bilateral kidneys, the bilateral ureters, and the bladder and urethra. The main function of the urinary system is to remove impurities and metabolic wastes from the blood by filtration through the kidneys. Through filtration, the kidneys can form primary urine from the useless components of circulating blood, which is reabsorbed by the glomerulus and then formed into urine. The main function of the ureter is to transport the urine formed by the kidneys through the ureter to the bladder. The main function of the bladder is to have the function of temporary storage of urine as well as the function of urination. When the bladder capacity reaches a certain level, a voiding reflex is induced and urine is expelled from the body. The main function of the urethra is to urinate, and when the bladder urinates, it can expel urine out of the body through the urethra. In addition, for men, the urethra is also responsible for the passage of ejaculation.