CBSE Class 10 Answered

Urine is produced by the nephrons of kidneys. Urine formation takes place in 3 steps:

i) Glomerular filtration - Filtration of blood under pressure in the glomerulus. This process ia called ultrafiltration.

ii) Selective Reabsorption - Useful substances from filtrate are reabsorbed by renal tubular cells and returned to blood.

iii) Tubular secretion - Separation of unwanted substances from blood and actively secreting them into the renal filtrate.

The concentrated urine is then taken to urinary bladder through ureters and stored there, until release.

This figure is given in the site:

http://home.bway.net/rjnoonan/humans_in_space/nephron.gif