There are about one million nephrons in each kidney. Waste products and excess fluid are filtered out of the blood inside the kidneys. The clean blood is returned to the body's central bloodstream through renal veins. The wastes and excess fluid leave the kidneys and are stored in the bladder as urine. When the bladder is full, urine is passed out of the body.
Nephrons are the microscopic filters inside the kidneys that cleanse the blood.
A nephron consists of a filter of tiny blood vessels called a glomerulus, which is attached to a tubule. The glomerulus filters the blood to remove wastes and excess fluid. The job of the tubules is to balance the amount of fluid and chemicals your body needs. It returns needed fluid and chemicals to the blood, and discards whatever the body does not need. The extra water and wastes is called urine.