Glomerulus. Transmission electron micrograph (TEM) of a section through a nephron in a human kidney, showing a cluster of capillaries within a renal corpuscle, also known as a glomerulus. Renal corpuscles are the blood filtration system in the kidneys and consist of many clusters of capillaries, as seen here. Two podocyte cells can also be seen. These extend many fine cytoplasmic 'foot processes' that terminate on the capillary wall. The tiny gaps between these processes form part of the selective blood filtration barrier across the wall of the capillary. The wall itself is selectively porous. Waste products from blood plasma pass from the glomerular capillaries into the spaces that surround them. This is called Bowman's space, from which the filtrates