Urine is the waste product of human body. It forms in kidneys. There are four steps of formation of Urine.
1. Filtration: The renal artery brings the blood which containing the waste material to the kidneys. Then it enters to the glomerulus under high pressure. Water and small solutes are filtered in the Bowman’s capsule.
2. Reabsorption: The filtrate passes through the thin walls of the Bowman’s capsule into the urinary or renal tubule. As it passes through the tubule, water and many useful substances are reabsorbed by the renal blood capillaries.
3. Secretion: The remaining liquid along with such as urea, uric acid etc are called urine and is collected in urinary bladder.
4. Excretion: Urine leaves the kidneys and passes into the urinary bladder through the ureters. When the urinary bladder is full, urine is passed out through the urethra.