The urinary system includes two kidneys, two ureters, the bladder, two sphincter muscles, and the urethra.
The urinary system works with the lungs, skin, and intestines - all of which also excrete wastes - to keep the chemicals and water in your body balanced. The urinary system removes a type of waste called urea from your blood. Urea is produced when foods containing protein, such as meat, poultry, and certain vegetables, are broken down in the body. Urea is carried in the bloodstream to the kidneys.
The kidneys remove urea from the blood through tiny filtering units called nephrons. Each nephron consists of a ball formed of small blood capillaries, called a glomerulus, and a small tube called a renal tubule. Urea, together with water and other waste substances, forms the urine as it passes through the nephrons and down the renal tubules of the kidney.