Urine formation takes place in the kidneys. This formed urine is then transported to the urinary bladder by the ureters, where it is stored. This stored urine is then passed out of the body by an opening in a muscular tube-like structure, called urethra.

The process of urine formation is given below in the diagram:

(a) - Glomerular filtration:
Blood containing useful substances (glucose, amino acids, vitamins, hormones, electrolytes ) and harmful substances (urea, uric acids, creatinine, ions, etc.) reaches the kidneys for filtration. This takes place through the semipermeable walls of the glomerular capillaries and Bowman’s capsule.

(b) - Selective reabsorption:
Wastes dissolved in water is filtered out as urine in the kidneys.

(c) - Tubular secretion:
Ureters carry urine to the urinary bladder.

Urine stored in the urinary bladder is passed out through the urinary opening at the end of the urethra.