Inside the kidney the blood vessels continue to divide until they become so small that their walls are too thin to hold back water and small molecules. Some of these molecules are excess body wastes. These tiny vessels are known as capillaries. The glomerulus is the filtering unit and contains the leaky capillary. The filtered blood (filtrate) that passes through the capillaries and the glomerular membrane collects into a sac called Bowmans capsule and drains into the proximal tubule. The water is recycled. Only one percent leaves the body, and is eliminated as urine. The filtered blood is returned to the body through veins.