The urinary system functions to eliminate waste from the body through urine and regulate water balance, electrolytes, and acid-base balance. The major organs are the kidneys, ureters, urinary bladder, and urethra. The kidneys contain nephrons, which are the functional units that form urine. Urine is formed through a three step process - filtration in the glomerulus, reabsorption of water and nutrients by the renal tubule, and secretion of wastes not reabsorbed.