Kidney as osmoregulator and excreatory organ

Kidney is not only excretory organ but it also act  as osmoregulator organ .Kidney keep the water concentration in limit.
 When the blood is dilute less water is re absorbed from the renal tubule thus large volume of dilute urine is produced.
When blood is too concentrated more water is re absorb from the kidneyll tubule thus amount of concentrated urine is produced

 deficiency of water in blood feel thirst.in the individual thus the individual drink the water.to restore water concentration .Similarly kidney also maintain the acid base balance in the body.acid are excreted in urine while the excessive loss of base is prevented .