The glomerulus is the network of blood capillaries surrounded by the renal capsule, the glomerulus is made up of 40 nephrons; anatomical and functional unit of the kidney ) come into contact with capillary ( endings of the arteries, so the blood to leak ).The structure of the glomerulus and the capsule is such that approximately 25% of the content of the blood is filtered towards the interior of the tubule, and that both the capillary endothelium and the epithelium of the capsule are permeable to all those substances that do not have one molecular weight of 65, 000.La filtration occurs because to be the diameter of the afferent arteriolesuperior to the of the efferent, the pressure in the glomerulus is very large, which leads to the occurrence by a physical process of the passage of substances towards the inside of the renal capsule. In this way produces a liquid called glomerular filtrate composed of water, mineral salts, ions, urea, glucose, amino acids, uric acid, etc.The two kidneys filtered through the glomerulus 125 ml per minute, which represents 180 litres per day. Obviously the rest of the nephron is adapted to alter that very high volume of filtration, blood returning most of the substances into only two litres of urine are removed on a daily basis.