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Kidney filtration. Coloured scanning electron micrograph (SEM) of tissue from a healthy kidney, showing the glomerular structure. The surface of a glomerulus is encased in podocyte cells (purple). These have branching processes that interlock. Below the surface, blood flows through the coiled capillary that is the core of a glomerulus. The function of the glomeruli is to filter waste products from the blood. Liquid passes from the blood through the narrow slits formed by the podocyte cells. After the reabsorption of certain substances elsewhere in the kidney, the liquid is transported to the bladder as urine. Magnification unknown. (KEYSTONE/SCIENCE PHOTO LIBRARY/STEVE GSCHMEISSNER)