The two kidneys play a vital role in homeostatis by processing the blood a waste fluid called urine. By so doing, the kidneys are carrying out two major functions. first is excretion of unwanted, and potentially poisonous,metabolic wastes produced by cells,notably urea, a nitrogenous waste product generated by the deamination of amino acid in the liver. second is osmoregulation, the removal of excess water and salts in order to maintain constant levels of water and salts in the blood.
the filtering mechanism blood flows at high pressure through the capillaries of the bowmans capsule and only one small molecules are forced through the wallsinto the first part of nephron the filtrate passes down the proximal tubule anndd... reabsorbs water, sodium essential salts, glucose and amino acids into the blood .. then the unwanted salts , urea, and water are left as urine