Selective reabsorption: The composition and volume of the glomerular filtrate are greatly altered when it passes through the convoluted tubule, the loop of Henle and the collecting tubule. Certain substances, such as, water, glucose, minerals are reabsorbed from the glomerular filtrate.  These substances are essential for metabolism of the body. The reabsorbed substances maintain the electrolyte balance of the body and the alkalinity of the blood. Some constituents of the glomerular filtrate do not appear in the urine, for example, glucose, amino acids and vitamins. These substances are called high-thresholdsubstances. , medical billing training online teaches you all these in detail.