Kidney anatomy, illustration. The microscopic structure of a kidney (sectioned at upper left) is shown in inset at right. The inset shows the arrangement of capillaries in the form of a filtration structure called a nephron. At upper left in the inset is the structure called Bowman's capsule. Within these structures, waste products are filtered from the blood to produce urine, and ion exchange takes place. Typical ions include sodium, potassium and glucose. Water retention (far left) takes place in the collecting tube (far right).