Amino acid is produced due to digestion of protein. This amino acid is used to perform various Biological functions. Excess and unused amino acid under the influence of enzyme named de-aminase takes part in de-amination process. In this de-amination process amine reacts with water to produce ammonia, thus ammonia is separated from the amino acid. Ammonia is a harmful substance for the body of the toad.
Along with blood, ammonia reaches the liver. There under the influence of an enzyme, urginase, ammonia by reacting with carbon dioxide produces urea and water.
You have learnt earlier that the afferent branches of the renal arteries dividing into numerous fine blood capillaries form the glomerulus. Through these afferent branches blood enters the glomerulus and passes through the capillaries. Due to high blood pressure, urea, glucose, and other soluble substances of blood enter the renal tubules crossing by the delicate walls of glomerulus and Bowman’s capsule. Refined blood leaves the Bowman’s capsule through different arteries. By the cells of the walls of renal ducts water, glucose, sodium chloride and other substances are absorbed from the solution inside these ducts. Residues are discharged with urea from the body by uretor.