The main function of kidney is urine formation, which completes in three steps:
Ultra Filtration: -
i) This process takes place in renal corpuscle.
ii) Due to blood pressure in glomerulus blood is filtered in Bowman’s
capsule. Here Bowman’s filtrate is obtained which consists of salts,
glucose, urea and uric acid.
iii) This filtrate is trickled down in the renal tubule.
Selective Reabsorption: -
i) This process takes place in network of capillaries.
ii) Here glucose and much of water is reabsorbed than some salts are sent
back to the blood.
Removal of Urine: -
i) Un-necessary water with urea, uric acid and other wastes traveled down
to pelvis.
ii) From there they are sent to urinary bladder through ureter.
Osmo-Regulatory function of Kidney: -
It is control of water content and other ingredients (salts and acids) in blood. If the blood contain too much water then more urine is produced, but if the blood is much concentrated then less urine is produced. The message for drinking water is sent to hypothalamus of brain (thirst center) to restore the blood consistency to its normal concentration. Above process to regulate the osmotic strength of the blood is collectively called osmo-regulatory function of kidney. Beside excretion, the kidney help to maintain the pH, blood pressure and composition of blood plasma.